General Car Audio Info/FAQ's/Questions...
07-11-2005, 04:44 AM
#1
Senior Member
SL Member
Thread Starter
Join Date: Apr 2005
Location: A-Town
Posts: 176
General Car Audio Info/FAQ's/Questions...
I haven't seen a post of this type around here, so I felt it useful/necessary to begin some type of thread where those new to the aftermarket audio world be able to consult that contains fact, as opposed to marketing schemes you'd find at shops, from manufacturers, etc. That said, I'll begin with a few brief points, and expand if you all deem it necessary. This comes from knowledge I've obtained whether from firsthand experimentation, read at some point, seen on a soundboard, in a lab, etc. Some of it will be copied and pasted from other places, etc in order to save my retarded, bleeding fingers from typing some stuff that might become muttled and hard to skim through because of my sometimes sleepiness, and laziness that might make things hard to understand, etc. That said, here's a little informatin to whet the appetite. Yes, I understand it's probably going to be a long read but, IMO, it's well worth it for information that might help when choosing a product to purchase. And yes, I've posted this in other places on the net, but it's still the same information that's good info regarding car audio that is a great read for beginners.
Without further adieu:
You get what you pay for?
the fact is, you don’t get what you pay for. not always. Its a problematic statement, especially with the overuse of the term "90% install, 10% equipment." Its a poor statement as well, but it really does apply to this situation.
lets compare. You just purchased DLS 3" wide range speakers which you’ve installed into your a pillars. I just purchased JL VR coaxials which I just put into my doors. our cars are otherwise identical in every other way.
you bought high end 3's and paid twice as much as I did for my entry level coaxials. who got better sound?
well, if we start getting random members to sit in our cars, the very VERY first thing they will notice is the lack of low frequency extension in your car. assuming we don’t have subwoofers, or even if we do, bass guitar will simply be more impressive in my car than yours. That alone will get me more votes for my car than you.
next thing to notice will be the top end. You will probably have some problems with your top octave. my VR tweeters wont have too many problems at least getting parts of the top octave. they might say I have brighter highs or something, or have to be told, but I will probably still get more votes than your car, though it will be closer.
the final problem will be actual location. this will require members who understand a thing or two about sound stage. when they sit in our cars, the first thing they will notice is my car has an image. center is within reasonable location, at a decent height. distribution will be kind of off, but again, we aren’t arguing perfection at this point, merely which "sounds better." When we sit in your car, we will notice that we hear whichever speaker is closer to us (driver OR passenger) and it will be so overpowering that it will sound louder than the other side, and phase will make some voices like center sound like there are two. I'm hearing double!
when it came down to money, You spent about twice as much on your soundstage than I did. yet my car outperforms yours in every way, shape, and form.
it becomes a tricky situation when we take into account that most members here aren’t going to be comparing installs, and that they will just be thinking about what door speaker will sound best. in the door. period. But, even here, its not quite so concrete as more money is better! those kodas at $80 each will yield much better off axis performance and higher low frequency extension than, say, digital designs midranges. practicality also enters into the setup, as those same DD speakers are over 3 inches deep!
and that even tang band speakers wont easily fit into the doors, despite having neodymium magnets.
Finally, threes always the ebay/forum phenomenon. say I stumble on a gentleman who happens to be selling his scanspeak revelator's for $200 the pair, he was just feeling REALLY nice. guess who's car is going to absolutely thrash any other in here who is also running $200 worth of midrange?
so, I don’t really think that you do get what you pay for.
Lacking Midbass?
the issue lacking midbass is something that should probably be out in the open, but the way its worded doesn’t work very well. many speakers are available that output plenty of Midas even at a very reasonable price. JL VR coaxials are one of them. I don’t see them often in cars. infinity reference, cdt classics, I see very, very often. why? they are in a group of a great many entry level speakers that don’t have basically any midbass capabilities at all. so yes, I can definitely see why we could use a tip that lets people know to expect a drop in midbass performance at the cost of improved volume capability for cheap upgrades.
but this isn’t to say that we cant choose speakers that can match the stock frequency response performance! we can reasonably easily find a great many speakers that have both enhanced volume and enhanced low frequency extension, as long as we aren’t shopping in the $30 speaker category! and even then there are a few models, if one looks hard enough!
I don’t see the relationship though, with being able to take more power and having less low frequency extension. I'll cheat with this example, and say what about your subwoofers? increased power handling AND increased LFE!
but seriously, we can stick with 6 inch speakers. what about those JL VR's? what about the XR's? what about adire kodas? what about kicker cmb is it? and what about the speakers that can get pretty close to as low as the stocks, if not well exceeding them? like DD w6's, peerless csc's, image dynamics chameleons? we can even cheat, and look at tang band 6's or JL w0's. talk about low frequency extension!
Amps adding/enhancing LFE?
I don’t see an amplifier enhancing LFE. you are stuck with the low frequency performance of whatever driver you buy. if you buy a 6.5" that only plays to 100 Hz, till play to 100 off deck power, till do that off an amp.
in fact, threes some evidence to suggest aping your speakers might DECREASE bass performance! as the gain goes up you'll be more likely to have problems with your bottom end, and be forced to have bad sound at high volume, or up the highpass filter cutoff frequency.
now, component sets sound best when accompanied by subwoofers? to use the term "component set" in this way is to suggest a component set works with a subwoofer better than a coaxial works with a sub! we can make many, many, many potential equipment combinations with both component sets and coaxials that are good and bad both! So it cant be that.
or was the statement intended to say that the speakers in front in the car work best with a subwoofer? again, simply not true! will it be better? probably. my mother sure wouldn’t agree! neither does my girlfriend!
the term "bass" is very difficult to discuss, especially when bridging a discussion between midrange drivers and sub-bass drivers. 100 and below? 50-150 Hz? is it a system we are trying to maximize low frequency extension up front, or do we not care, and use 8 inch subwoofers in he back playing up to 200 Hz, so long as we get all octaves covered? It makes things more difficult.
regardless, I try to use relative terms, so no one gets confused. thus, the bottom end of 6.5 inch speakers becomes low frequency extension. the very very bottom octave of subwoofers becomes low frequency extension, too. in terms of frequency values, the same frequencies for 6.5 lfe becomes subwoofer top end, etc. and that even changes based on size.
but the relative discussion makes for absolutely ZERO confusion when someone tells someone else "yeah, these speakers have a lot of bass". then based on that tip, someone makes a purchase and is ____ed his speakers don’t play low at all!
Soldering Connections, and RCA’s
There’s no way I can advocate solder to make connections. the name of the game in a car is "preserve the value of the vehicle", not "make the best connection that’s humanly possible". there’s a reason that the vast VAST majority of high end shops out there use t-taps rather than solder, and its not entirely speed! Its far more important to have a high resale value on the car five years from now than a connection that will last forty years rather than twenty years! if your taps are falling off after two weeks, its not a sign you need to solder, its a sign you should be working harder on making a solid tap!
cables themselves. there is no way I can advocate buying kimber cables over radioshack gold series every time. noise floor in a car is ridiculous as it is, but even with the car off, in a quiet neighborhood, I get ZERO noise in my own car. I don t have kimber, I have el-cheapo!
now, I can definitely see instances when high end cabling would be needed. I was routing some RCA's in my car in a previous install right across the fuel pump. got some noise! throw in a higher shielded cable, and everything was fine. does that mean I needed to buy $70 rca cables to get from the radio to the rear seats? no way!
as for the connections, its all about long term reliability, and nothing else. are you gonna unplug your RCA's three times a day? will they be tweaked this way and that, will there be pressure on them by a trim piece, or when stuff gets thrown into your car? you’d be a fool to buy radioshack cabling! My own amplifiers are in their own designated areas, foreign objects cant access them, and I don’t tug on the cables. why should I buy cables with burly and bulky ends?
as to those cables themselves, I was doing a mustang a couple years ago. we had two cables in the car, monster and audiopipe. the monster turned out to be noisy as heck! they were routed in the SAME spot, and the monster cable induced more noise than the audiopipe! haws that for high end! so sometimes, a cheaper cable can really be the better one from a noise perspective!
as for the head durability problem, another friend and a ford ranger, with knu top end rca cabling. Every time we unplug the cables, the heads start to unscrew! talk about annoying! if he bought the uber UBER cheap cables from radioshack, he wouldn’t have problems with the heads coming unscrewed! not that I am advocating the ultra cheaps in this case, I think he would have had a great deal of problems with noise and connection reliability with kids crawling around the back of the truck to have radioshack rca back there, but when you are paying triple digit numbers JUST for rca cables, there is NO reason I should have to threadlock the heads on!
so what IS better? radioshack? monster? kimber? audiopipe? well, I think its gotta be application based with a heavy emphasis on budget. It definitely surpasses the help a one sentence tip could give on the matter, unless that tip said "when in doubt, let your budget do the talking"!
Dynamat Prevents Rattle?
I think its a very good idea to be promoting the fact the dynamat will probably not prevent rattles. But absorb vibrations? Imp pretty sure most of dynamat if not all is the type that merely raises panel resonance to prevent ULF (ultra low frequency) waves from causing resonance issues. regardless, a tip thread should be unimpeachable.
but lets not forget ALL the applications if we are going to say it cleans bass and makes bass louder! we use it to eliminate road noise, engine noise, raise bass efficiency, seal doors better than stock, etc, etc, etc! It might be better to leave the rest of the practical apps of dynamat entirely out of the tip thread, a tip thread is to give practical advice on how to act in a certain way as a reference.
thus "dynamat is not designed to prevent rattles" is probably a sufficient tip.
but here's the ultimate in offensive results of dynamat use. Ever install dynamat extreme behind your door speakers? reflections off the aluminum plate often causes cone interference and make your sound FAR worse! But those who were willing to spend $40 or more on those small pieces of mat and then thought their performance increased would be offended if we insulted that use of money.
Bass, truly omni directional?
I wish bass were omni directional, but its not. its a simple test though. put your HT subwoofer on the right side of your room. when something explodes on screen, does it explode on the screen, or does it explode off to the right?
same thing in the car. all my sub-bass comes from behind me. I wish bass were omni directional, I could put subwoofers in the trunk and they would sound like they are on my hood! But I have to live with bass coming from behind me.
Fire Direction relates to response?
we can load the subwoofers off the rear deck, we can down fire, side fire, put them into the cabin, even mold them into the dash! its redundant and unnecessary information to discuss rear and forward firing exclusively here, especially when its incomplete just discussing those two topics, much less including all others. eddie runner spent more time discussing box facings than I have in this thread all together. its a complex subject!
different subwoofers, boxes, and firing positions will provide different bass performance results. not better, not worse. different for different desired effects/applications.
Capacitors?
People saying that caps help keep voltage constant around 14.4 V, etc. I'm sick of reading stuff like "get a cap, it'll help blah, blah, blah..." The following information is excerpted from CarSound's great cap debate thread, or whatever they choose to call it. The excerpted portion that I am pasting here is all information posted by Richard Clark, whom is a moderator there, and one of the godfathers of car audio. He even offers $5,000 for anyone that can disprove him, but the catch is you have to have factual scientific data to prove it. There are several books that both he and Dave Navone co-authored about car audio, and have the data included. I'm sure there is a PDF somewhere as well, but this is a long read of information that proves the "theorys" related to cap functions incorrect, and untrue. Read through the whole thing, and gain an understanding of caps, and their use, and what they actually do before trying to debate this information. If you have a dispute with it, perhaps you should contact Mr. Clark. Caps do nothing except possibly, not defiantly, possibly help dimming. They aren’t guaranteed cures for voltage problems/lacking voltage/falling voltage, etc…
Lesson 1
Ok “powertrip” how about we have a discussion in basic electrical theory? At the end of this thread you should be the one that can explain to the world that according to ohms law it is impossible for these things to do any good. That is of course if you can admit that they do obey ohms law. We will do this a little at a time so how about you humor me and stick to my questions. We will do them a couple at a time so everyone can follow along. Let’s do a little calculation. Suppose we have a resistor that is .017 ohms (seventeen milliohms). I think that is what you say the ESR of the giant caps is.
The ones I have seen have measured higher but I will give you the benefit of the doubt. According to ohms law how many volts are dropped across .017 ohms if 100 amps of current are flowing? How about if we up the current to 300 amps? Let’s establish the answers to these questions before we go any farther. If we can't agree on the answer to this there is no hope we will ever get to the truth.
Lesson 2
Thanks David you are exactly right. If anyone wants this explained please ask David to clarify it. If everyone is going to follow this and understand fully the final conclusion it is important that no one miss any steps. There will be about ten lessons. Since power trip has left the building we will continue with the rest of the class. ESR stands for equivalent series resistance. This means exactly what it sounds like. It means that if we have a source of voltage it will behave exactly as if it has a resistor of the same value in series with its output. An amplifier has ESR, a power supply has ESR, a battery has ESR, and yes, a cap has ESR. Components have ESR’s because we do not have perfect conductors to make things from.
And now for the homework. Last night we learned that if 100 amps flows through .017 ohms there will be a voltage drop of 1.7 volts. And if the amp flow increases to 300 amps the voltage drop will increase to 5.1 volts.
For the sake of theory only let’s say we have built the largest cap in the universe and it has billions and billions of Farads. Its plates are made of a newly discovered material we'll call unobtanium. This new material has no resistance therefore our super cap has an ESR of ZERO ohms. We then charge the capacitor to 14.2 volts. We then place a resistor with a value of .017 ohms in series with one of the terminals of this cap. The question is: If we place a load that draws 100 amps from this cap what will the resulting voltage be on the load side of the resistor? What will the voltage be on the cap side of the resistor? What about if we increase the load to 300 amps? What will the voltages be on each side of the resistor?
Lesson 3
Ok now that we have studied ESR and understand what it is and it’s effect on the working of a circuit we will move on to another subject. But don’t forget about ESR as it is one of the important final building blocks in our search for truth about caps and we will come back to it. Today we will review the important concepts about total energy storage in a device like a cap. This has been covered in earlier posts (and I will say quite correctly) but I am going to expand on it as well as reiterate it for those who did not get to read it. Besides, I think I can simplify it a little.
In electronics, we measure power in watts. Wattage tells us how much work a device can do. But a wattage rating does not tell us anything about how long we can sustain that work. When we add the element of time to our wattage, we use a value we call Joules. A joule is a watt second. This means that one Joule of energy can provide a watt for a second. Ten joules can provide a watt for ten seconds or ten watts for one second or five watts for two seconds one hundred watts for a tenth of a second, and so on.
The formula for determining the total joules stored in a capacitor is very simple. We take one half the capacitor’s value in farads and multiply it times the squared charge voltage. For example a one farad cap charged to 14 volts would be .5 X (14x14) = 98 or .5 X 196 = 98 Joules. A 20 farad cap charged to 14 volts would be 10 X (14x14) = 1960 Joules.
There is a very important concept to understand about energy storage. A capacitor actually stores electricity.
Batteries don’t. Batteries have the potential to produce electricity by means of a chemical reaction but caps actually store electrons on their plates in the form of an electrostatic charge. In our next two lessons we will learn why this is important to know.
But first, the homework. This is a “think about it question”. We have learned that a Joule is a watt second. A Yellow top battery is rated at 65 amp hours. This means it can provide 65 amps for an hour. The question is how many Joules does this represent? Since this is a thought question, it would really help if whoever answers would show us your math.
Lesson 4
In the actual real world the voltage of the battery would drop a little from its open circuit voltage of 12.8 volts with a 65 amp load. In the case of the yellow top its actual voltage at 65 amps is about 12.2v when fully charged. By the end of the hour it would be down to about 10v. If we use 11 as an average our answer would be........ 2,574,000. Now that's still a lot of joules! Now actually this is not enough to totally kill the battery but at this point there isn't much left in it. This brings us to a very important fact. The energy in a battery will be depleted almost completely by the time it is down to 10 volts.
Lesson 4 (continued)
By the time we have removed those 2.5 million joules from the battery it probably doesn't have more than a hundred thousand joules left. We can almost totally deplete the battery's energy and never drop below 10 volts. This is because the battery doesn't store electricity. It stores chemicals. A chemical reaction produces the electricity. Storing actual electrical charges is very inefficient.
Look at our poor capacitor. Even if we made one as big as a battery it would still only be good for perhaps fifty to one hundred thousand joules---less than that left in a nearly dead battery. But if that were not enough there's more bad news. This exercise will be tonight’s homework.
A capacitor is like a gas tank in a car. The pump can only remove gas down to the pickup point. Any gas below this point can never be removed by the pump. If we charge a 20 farad cap to 14 volts we know from previous lessons that it will contain 1,960 joules. If we use that cap in a system and load it till it drops to 10 volts along with our battery how many joules will we have removed from the cap? How many joules will remain in the cap that we can never benefit from if our system never drops below 10 volts?
Lesson 5
In our last lesson we learned that caps actually store charges on their plates. And of the 1960 joules stored in a 20 Farad cap, 1000 of them sit at a potential below 10 volts. This means there is no way they can ever be used by an operational audio system. Today we will look at another loss factor. It has to do with the loss factor due to the ESR of the cap.
We have already studied voltage drop due to ESR but now let’s view it from an energy/watts standpoint. Let’s clarify things. The power delivered to the stereo by the battery and alternator bypass the cap. They merely flow by its terminals. If the cap charge is lower than the battery/alternator potential current will flow INTO the cap until it reaches equilibrium with the Battery/Alternator. If the B/A potential is lower than the charge potential of the cap current will flow OUT of the cap to the battery and or the amp.
Always remember that voltage always flows from the highest potential to the lowest potential, just like water. Current does not however flow into the alternator even if it is lower than the battery and cap because it has diodes on its output that only let current flow FROM its output. Now whenever any current flows into or out of the cap it must pass thru the ESR of the cap. The resistance is really distributed throughout the cap but it behaves just like it was right on the output terminal as in a series circuit location in the circuit loop does not matter. Now suppose our 20 farad cap is charged to 14.2 volts and we place a load on its output. This load is the same one that we used in lesson 2 to cause 100 amps of current to flow from our unlimited capacity cap. Only now we have our smaller 20 farad cap.
Lesson 5 (continued)
We know that if 100 amps of current flows out of our cap, those 1.7 volts will drop across the ESR of .017 ohm. This will cause the output to drop to 12.5 volts just like it did with the unlimited cap.
This means that the load (100 ohms resistance) will be consuming 1250 watts from our cap. 12.5 volts x 100amps = 1250 watts. The total wattage output produced by the cap is 1420 watts. 14.2 volts x 100 amps = 1420 watts. Unfortunately 170 watts of power will be lost in heat in the ESR of the cap. This represents a loss of 13% of our total usable joules (960) at this point. Now tonight’s question is if we increase the current draw to 300 amps (300amps x 14.2volts = 4260 watts), how many watts will be dissipated in the ESR of the cap and what percentage of the total 4260 watts does it represent? Of our total usable 960 joules, what percentage will be left for the stereo?
Lesson 6
Ok before the next lesson let’s review lesson five. When I checked the posts no one had the correct answer of 56% but some were close. The important part is that everyone seems to understand the loss mechanism. From lesson five we see that the energy we can get out of a cap is inversely proportional to the rate that we try to take it out. This is because the ESR that is in series with the output stays constant regardless of the load. At very high power levels, this ESR can amount to a sizeable amount.
In an earlier lesson we learned that the ESR causes a voltage drop proportional to current flow. When voltage is dropped across a resistance heat is created. Lesson five taught us that with 100 amps (flowing from a cap with .017 ohm ESR) we lose 13% of our joules as heat when we try to remove them. If a cap has an ESR of .017 ohms, and 300 amps flows we will lose 56% of the stored energy when we try to remove it. In our giant cap example with 300 amps of current, we will lose this as 1530 watts of heat. This is the same loss mechanism that causes a battery or amp or power supply to get hot when they are delivering high power levels. Virtually all voltage sources have at least some ESR. At this point we should have a good understanding of how ESR affects a component. The next logical thing to cover is ESL.
ESL stands for equivalent series inductance. Just like the ESR it can be modeled as an inductor in series with the output of our capacitor. Now everyone in car audio knows what inductors do. They resist a change in current flow. Their most common use is in speaker crossovers. When used in series with a woofer they let the slowly changing low frequencies pass, but stop the fast changing high frequencies. The reason an inductor does this is because it behaves like a resistor that changes value with frequency. Unlike a capacitor that decreases in value with increasing frequency an inductor decreases in value with decreasing frequency.
Lesson 6 (continued)
Now I have been told that the ESL value of the giant cap is 0.2 mh. Somebody check my math but I think this would put the reactance of the cap near .063 ohms at 50 Hz. This means that if we wanted to refresh our amps at a rate of 50 Hz (seems reasonable if we were playing bass real loud) our ESL of .07 ohm would be in series with our .017 ohm ESR for a total value of .08 ohms.
Now we know from ohms law that if we try to get 100 amps through .08 ohms we will have a voltage drop of 8 volts and at 300 amps the drop would be about….well it’s pretty clear that we will be left with less than a fraction of a volt if we start out with only 14.2. Is everybody still with me? I know it’s not good news but I’m not making this stuff up.
Now for tonight’s lab lesson to prepare us for lesson 7. Tomorrow, I will post the results of the following test. If you want to check me, go to Radio Shack and buy the following: Bulb # 272-1127, Socket # 272-360, and a nine volt alkaline battery. For the battery a Radio Shack is ok but a Duracell is better. Make sure it is fresh!!!!!
Wire the socket and connect it to the nine volt battery and record how long the bulb stays lit. Be prepared to wait for a couple hours. Charge a giant cap to 14.2 volts and do the same with it. Be prepared to wait about an hour. Charge a 1 or 1.5 Farad cap to 14.2 volts and do the same. This will take only a few minutes. Record the times and we will discuss the importance of this in our next lesson.
Lesson 7
Ok in last lesson I left everyone with instructions to duplicate the results of the test I am going to post tonight. The purpose of this test was to put the capacity of even a giant cap in perspective. As I have pointed out in earlier lessons storing electrons in the form of a charge on a plate is not really very efficient. Some folks think we should stand in awe of a value like 2000 Joules. Well our test tonight puts some reality in this value. If we perform a test like described in the end of lesson 6 we come up with the following results.
1.5 Farad cap lights the bulb for about …………5 minutes and 28 seconds
a giant cap lights the bulb for about……………. 54 minutes
a nine volt alkaline does so about …………………. 2 hours and 14 minutes
did anybody get results similar to these…….are we in agreement on these numbers ?
Lesson 7 (continued)
As for the relationship of these numbers, each of these units has a higher ESR than the previous one. The highest ESR in the group was the nine volt battery. It actually has enough energy to light the bulb far longer but since its ESR is fairly high it loses a lot of its energy as heat internally. But even still it should be apparent that it holds more energy than the giant cap and a whole lot more than a 1.5 farad unit
For now I do not care to concern ourselves with the meaning of this ---we will cover it in the closing. Before going on let’s review a few facts. In lesson 3 we learned that a giant cap can hold 1960 joules at 14 volts. In lesson 4 we learned that only 960 of them sit at a potential above 10 volts. In lesson 5 we learned that if we want to use them at a rate of 100 amps we will lose 13% of the 960 that are left.
If we use them at a rate of 300 amps we will lose 56% of the 960 which will leave us with only about 500 usable joules. And these losses are only for the ESR mechanisms—they do not include the ESL mechanisms that could actually be higher if the demands are quick enough.
It has been suggested that the purpose of these giant caps is to provide quick energy. It has also been suggested that they are for slow energy.
I am not sure what is being claimed so I guess I need to cover both situations. As for slow energy I think the previous test could put that thought out to pasture. For long term energy one of these units is less useful than a nine volt battery and to compare it to a car battery is really useless. After all what good is 500 useable joules when we have over 2 million in the car battery? It should be obvious if one of these devices can be of any use at all it will have to be able to provide energy faster than a car battery. But before we get to that issue lets cover the behavior of alternators and batteries under dynamic load conditions.
Tomorrow is Saturday and I will have time to measure the response time of a few alternators. This will enable me to model my closing explanations more exactly. I will post the results of these tests tomorrow night.
Lesson 8
For this lesson I have done some actual measurements. Here are the test conditions: To measure voltage we used an Audio Precision with a DCX module. It is accurate to three decimal places. For sample time we chose 40 samples per second. For the non audio system test I used a KAL carbon pile load tester. It can do power tests on 12 volt charging systems up to 1200amps continuous. The audio system consisted of a couple of Rockford 1100 amps bridged into four ohm nominal speakers. The alternator was a stock Delco 80 amp CS type unit.
Lesson 5 (continued)
Its case temperature was monitored by a Raytek ST2L IR sensor. Engine speed was regulated with a Thexton #398 IACV tester. The music material was the SPL track # 30 from the IASCA competition disc. The battery was a Stinger spb-1000. All voltage measurements were done directly at the terminals of one of the amps.
Chart 1 Alternator/cap/battery test with 200 amp dummy load
For this test we monitored the voltage of the car with the stereo turned off. With the car running the voltage can be seen to be stable at about 13.7 volts. After 22 seconds (The horizontal scale is 100 seconds-10 sec per major division) we applied a 200 amp load. The voltage can be seen to drop to 11.6 on both traces. This test obviously exceeds the ability of the alternator to keep its regulation set point so its voltage falls. The drop can be seen to be nearly instant (steep curve) until about 12.5 volts where the battery starts to supply a significant amount of the power.
Ultimately the voltage drops to 11.6 and at 26 seconds we turn off the load. The voltage then starts to rise to the regulator set point as the battery is recharged (yellow curve) and as the battery and cap (green curve) are recharged. At a time of 50 seconds I turn the motor off so the alternator stops. The voltage then droops down to the float voltage of the battery—about 12.7. The only reason for the small difference at 50 seconds is because I couldn’t get the timing of the engine shut-off exactly the same every time. I did it several times and these two are within one second. That was as close as I could get it.
I am able to see no difference from these measurements. There are microscopic differences but I believe they are due to the alternator temperature. Alternator regulators are usually temperature sensitive. As they get hotter they tend to fold back. For this reason we let the unit cool off between each test and closely monitored the case temp throughout the tests. For this reason I believe that none of these measurements are meaningful to more than a couple tenths of a volt.
Chart 2 Music tests with an audio system
Note: Between each test the alternator was allowed to cool and the battery was charged until an automatic charger said it was topped off.
Purple curve
For our first test we played the system with the engine off and no cap. The result was the purple trace at the bottom. We played the system as loud as we could get it that seemed to produce no audible distortion. This was track 30 of the IASCA disc. It starts off with fairly low level sounds for the first 34 seconds. In order to insure the electrical system was stable we did not start the measurement until we were 20 seconds into the song. This means that our 0 starting point is: 20 on the CD counter. The battery was able to maintain its voltage just below 12.5 until the loud bass hits at 34 seconds (14 seconds into our chart) At this time it dropped to about 11.5 and had a few large variations due to the music. According to the computer calculations (third chart) the average voltage for this test was 11.7volts. This test was done as a baseline for the following tests.
Yellow curve—no cap
For this test the volume was left as it was for the baseline test. The engine was started. Notice that at low volume the alternator was able to maintain about 14 volts. When the loud music hit the voltage dropped to about 12.5 where it remained except for a few short moments where it actually climbed back to over 13.5 volts. The computer averaged calculations for the average voltage during the 100 seconds of this test was 12.973 volts.
Red curve—cap added
This test was identical to the previous test except the cap (15 farad type) was added 6 inches from the amp with 4 gauge wire—no relays or fuses. The red curve seems to overlay the yellow except that the actual peaks don’t rise as fast or as high during the brief quiet moments. I feel this would be due to the alternator having to recharge the cap. The voltage on loud passages hovered around 12.5 volts. The computer averaged calculations for this test show the average voltage to be 12.878 volts. I see no meaningful differences with or without the cap. I certainly don’t see the voltage sitting solid at 14 volts.
One note I might add is that this was a two thousand watt system driven right to clipping and the average voltage stayed above 12.8 with a stock 80 amp alternator. Under these conditions the battery would never discharge!
The green and blue curves were done just for kicks while we had the system set up. In both these tests we turned the volume up until the system was very distorted. This placed a severe load on the alternator and caused the voltage to dip as low as 12 volts. The curves seem to follow each other so closely that unless you have a good monitor it is doubtful you can tell there are two curves. The average voltage for these two curves was both 12.277 and 12.295 volts. If this volume were sustained for very long periods of time this battery would discharge.
Any questions? Please ask -- I will give everyone a chance to ask them before I sum this all up in lesson 9.
Lesson 9
Now that we have had time to study theory in each of the 8 lessons and the results of the actual tests on a real system it is finally time to bring this discussion to a close. Unfortunately, when this thread started I was unable to explain the concept, as it was obvious that many of the people posting responses just didn’t have a good grasp of the way things really work. Those of you who have taken the time to follow the lessons should know by now why I was so frustrated at the arguments that were so illogical. It is important to keep in mind that this is a technical forum, not a marketing forum. I do not care or want to know about companies or brand names.
Nothing I have said was ever meant to disparage a particular product or company and I would appreciate it if in the future we could always keep that in mind. We should be able to discuss the merits of radial vs. bias ply tires without caring if they are made by Michelin or Goodyear.
In car audio we have little choice of how we are going to power our systems. Presently we have only four things that are practical. Each of them has its own characteristics that incorporate good points and bad points.
Let’s review them
The battery--this device has the ability to provide a very large amount of current. But due to its nature the current is provided at a voltage that is less than optimum –at least for a high powered stereo. Since its float point is 12.8 volts if fully charged, it can provide current only at voltages that are proportionally lower than 12.8 Volts.
The alternator—this device is electronically regulated at a point that allows it to recharge the battery. The alternator is usually designed to output voltage in the 13.8 to 14.5 volt range. Because its output is actively regulated it attempts to maintain this voltage with varying load conditions up to the point where it’s output cannot keep up with the load at which time it’s output drops off very rapidly. While relatively tight regulation is the strong point of the alternator it’s weak point is that it simply is not practical to obtain one that can provide large amounts of current like a battery is capable of.
The capacitor. The advantages of a cap are that it can charge up to whatever the highest voltage source in the system is, (in a car this would be the alternator) and provide current at this elevated voltage. The down side of a cap is that it cannot store very much total energy and only a portion of this energy is available at a usable voltage potential. The fourth type of device is an electronic voltage regulator. These devices have not been part of this discussion so I will pass over them for now.
Now modern car audio amplifiers are capable of consuming enormous amounts of power. Even with efficiencies in the range of 60% to 90% an audio system is capable of drawing hundreds or thousands of amps from the cars electrical system. Typically, the audio system is larger than any other electrical device in the car including the engine starter. Fortunately for the car, the demands of an audio system are rarely continuous in nature. The very nature of music rarely demands more than a duty cycle of 10% to 20% from a power standpoint. This means that the audio system is demanding short term, but repetitive peaks of current from the electrical system.
The primary source of this power is the alternator. It should be considered primary for two reasons. The alternator is the only first generation source of power. It ultimately provides all the power for the system either directly or indirectly by restoring power to the battery or cap. It is also primary as it is the power source with the highest voltage potential. In an electrical system current always flows from the source of highest voltage to circuits of lower of lower potential.
All three devices can be used in a system to great advantage. But the dynamic conditions present in a music system determine the role each device plays and to what degree. To understand this lets consider a low current drain condition. In this scenario the alternator will be at or near its set point.
This voltage is designed to be high enough to charge the battery meaning it will be one or two volts above 12.8 volts. This means that the battery will actually be a continuous load on the alternator and provides no power to the system. The size of load it presents is determined by the state of charge of the battery. The higher its state of charge the smaller the load will be. A cap if present in a system in this state will present a load for a finite amount of time until its charge voltage reaches equilibrium with the alternator.
Unlike the battery, the cap will cease to be a load after it is charged except for a factor known as dissipation, which for all practical purposes can be ignored in this application unless it is excessive. Under these circumstances, as long as the alternator can maintain its set point, it will provide all the power for the music system and the rest of the cars accessories. The battery and cap may as well not even be in the car.
Now if we increase the current demands of the music system to an amount that taxes the alternator its output voltage will begin to drop. Even so the alternator will continue to be a source of current to the system –i.e., the car, music system, and battery. It is at this time that the cap will begin to discharge and begin to augment the alternator as a source of current. The degree to which it provides current to the system is dependent on the actual voltage at the alternators terminals. Only when the alternator begins to drop below the caps charge potential does current flow out of the cap.
This is a continuous process and the current provided by the cap tries to maintain the voltage at its charge potential. The degree to which it can do this is dependent on two things. The current provided by the cap is limited to the total capacity of the cap and any series reactance’s (resistive or inductive components) that are part of the cap. The instant the cap starts to output current its charge potential begins to drop.
Now just what can we expect the cap to provide? Suppose we happened to have a cap charged to 14 volts, with a total reactance (made up of either resistive or inductive components) of about .017 ohm. We could figure that at the first instant of discharge it could provide ten amps at 13.83 volts. Of course if we were playing the system at a level enough to load our alternator, ten amps is not likely to provide much relief. But perhaps 30 amps might help—at this modest level our cap could begin to provide current at a potential of 13.5 volts. (lesson 2).
Of course this voltage level would drop at an exponential rate commensurate with the discharge curve that is standard with caps. No doubt the cap could help out a hundred amp alternator with the addition of an extra 30 amps even though it might be for only a brief instant. But it is sort of interesting that at even this modest power level of 130 amps (100 amps alternator + 30 amps cap) the cap is unable to maintain the voltage at 14 volts.
Of course in this scenario we are sitting at 13.5 volts for a brief instant and our poor battery is unable to help at all as its potential is at a lowly 12.8 volts. In fact the battery is still a load on the system!
Now what if we get serious with our stereo and we really crank it up? Lets say we have something like a manufacturers demo van with lots of amplifiers that can draw hundreds of amps on musical peaks. Lets pick a nice round number like 500 (“Cade” said 490) amps. Lets say we have a 200 (“Cade” said 190) amp alternator. Typically such an alternator can maintain a voltage near its set point up to perhaps 80% of its rating-after which its voltage begins to drop as it provides large amounts of current. As I am not familiar with all the different alternators lets just assume these assumptions are close and our alternator is putting out 200 amps. Well our amplifiers in an instant are asking for 500 amps so what happens?
In any constant voltage system when the current capability is exceeded the voltage drops. So let’s say our alternator voltage starts dropping. What does our cap do? Since its charge potential is at 14 volts it starts to discharge and provide a source of current. Since the cap is now sharing the load with the alternator it is called on to provide what the alternator can’t—that would be 300 (see footnote) amps.
What happens to the terminal voltage of our cap when 300amps is flowing? Well for starters, the voltage tries to drop nearly 5 volts inside the cap before it can even get out. Not in a short time but instantly. There is no time constant in the formulas for ohms law. They are instantaneous calculations! But wait. The voltage doesn’t really drop to 9 volts because we have our battery sitting in reserve waiting at 12.8 volts.
Our cap lets our poor alternator down as the voltage plummets and when things hit 12.8 volts our battery jumps in and starts to take over. The battery with its enormous storehouse begins to provide vast amounts of current until things lighten up for our poor cap and alternator. Of course we could add another cap to halve our ESR loss to only 2.5 volts but that would still cause the cap terminal voltage to drop to 11.5 volts.
Let’s see how many caps of this spec we would have to add to keep the voltage at 13.5 for even a few milliseconds. We would need a cap bank with a total ESL of about .001 ohm. Gee it looks like it would take over thirty caps paralleled to maintain 13.5 volts at 300 amps for even a brief instant. And let’s hope we don’t need to do this for long, as the total power contained in thirty units is only about what is in a dozen 9v alkaline batteries! (lesson 7)
It should be clear that if the voltage doesn’t drop the caps don’t do anything. The voltage MUST drop for them to start discharging.
Now, is it possible to have a steady 14 V because we added caps? I don’t think so.
When considering a replacement for your stock speakers please realize that they are designed to output bass, mid bass, AND highs. If you replace the speakers with something else and they take alot more power, you will most likely end up with much less bass and mid bass.
If you replace the stock speakers with a component set you will get mostly mid bass and highs. If you use an external amplifier it will be a little better for bass, but component sets sound best when you accompany them with subwoofers.
Make quality connections or nothing will work right or for very long. Use Gold/Platinum ends if possible.
Don't skimp on connections.
Dynamat DOES NOT STOP RATTLES. It absorbs vibrations which will (long story short) clear up the sound and make your speakers/subwoofers louder.
Subwoofers / Amplifiers
Human hearing is 20Hz - 20,000Hz. Anything over 20,000Hz you will not hear. Anything under 20Hz you will feel but not hear.
When matching an amp with a sub or a speaker to an amplifier/Head Unit, make sure the RMS rating on the amp is less than or equal to that of the sub, for that impedence (ohm rating).
As a general rule the best mix of SPL and SQ for subwoofers will be in a box built to the specifications of the subwoofer company for that specific sub.
Keep in mind the wattage ratings on amplifiers are usually at 14.4 volts or close. This means if it draws alot of power and the voltage drops to 12 then the amplifier will not be outputting as much power. The only amplifiers that combat this effect are ones featuring a "Regulated Power Supply" like the JL Audio Slash series
When tuning an amplifier do not turn the gain way up or put large amounts of bass boost on;
Clipping is when the shape of the sound wave becomes less round and more square.
You may safely give the subwoofer or speaker less power than it can take, but make sure you do not get distortiona and clip the signal
It is also possible to give a subwoofer much more power than is recommended but at this point it is much more sensitive to distortion and will blow much much easier. If you do not know about this already then do not overpower or underpower you speakers or subwoofers! (Or get professional help)
Make sure your fuse is the right rating!!! Too much and it will let your amp kill itself. Too little and the fuse will blow all the time.
When adding/moving a battery to the trunk make sure it is in a sealed enclosure. Your body does not act well to toxic gases.
Make sure you use a large enough wire (smaller gauge) to carry power and to ground. If the wires are too small they will hold back your system and could possibly overheat and melt.
Head Units
For most cars you will need a mounting bracket to mount an aftermarket stereo because the stock stereo is not a regular size or shape.
Most recievers are DIN or Double-DIN sized. Almost all mounting brackets accept DIN sized stereos, but there are a select few Double DIN kits for our cars.
A regular CD will hold about 20-25 songs. An MP3 cd can hold 256 songs. Make sure you get a CD player with MP3 support even if you do not plan on using it. You will thank me later.
Some recievers support WMA also, which is like an MP3 but compressed differently. If you rip music using Windows Media Player you NEED WMA support!
Many recievers are Satellite radio ready, so if you use Sirius or XM get a head unit that can control the reciever instead of having 2 things to worry about
Don't use the loud, Magna Bass, or other stupid functions on your reciever. They just distort the sound and can cause harm to your speakers and subwoofers (to an extent)
The more band the EQ is the more control over sound quality and sound shaping you will have.
Preamp outs are necessary for decent subwoofer performance unless you are going to use a quality line converter.
In Dash DVD
It is only illegal to have a screen that the driver can see if it has motion (ie movies, etc)
A screen of text is not illegal even when moving.
It is illegal to have an in dash DVD player wired to be able to watch movies while driving if the screen is in view of the driver.
Most units have a seperate brain box that is quite large and must be mounted outside of the area of the reciever with the screen. If you dont want to mount a seperate box look at the select few that do not have them (VRX745VD now re-released by clarion as VRX755VD with a few new features)
Wiring an Amplifier
The first thing you should do is purchase a pre-assembled amplifier wiring kit if you are not very knowlegable and experienced in this.
Start with the power wire; Connect the + power wire, with NO fuse in the fuse holder, to the + terminal on the battery. MAKE SURE THE FUSE IS WITHIN 12 INCHES OF THE BATTERY!!! I CANNOT STRESS THIS ENOUGH!
Next run the power wire along the other wires going down toward the passenger side fire wall. Use Zip Ties to secure the wire along other wires, this way there is no chance of it ever getting cut or damaged. To get the wire to the trunk you may do one of 2 things. First you could take out the seat on that side, and run the wire completly under the carpet, which will end up coming out under the rear seats. You may also run the wire under the plastic trim that goes along the floor and then up through the sides of the rear seats Once you get the power wire to the trunk, or wherever you are wiring the amplifier, move onto the signal wires.
Remove the stereo from the center console using the instructions above. Connect the Amplifier Turn On wire you got in your wiring kit to the corresponding wire off the back of the stereo. This is usually blue.
Next connect the RCA cables if you are using them to take the signal to the rear of the car.
Route the RCA + Amp Turn On wire either through the plastic trim along the outside of the car or under the carpets like before, but DO NOT LET THEM TOUCH RUN ON THE SAME SIDE AS THE POWER WIRE TO AVOID INTERFERANCE.
Pull all the wires through to the trunk.
To ground, find a metal spot close the the Amplifier and scrape away all the paint in a small 1" diameter circle(I like to remove the paint with a wire brush attachment on my drill then sand away after that to ensure removal of all the paint). Drill a hole in this circle and then take the ground wire and a metal (preferably grounding grade(green usually))screw, and screw the ground wire into place. The more bare metal and less paint on the metal panel, the more solid the ground connection.
Mount your amplifier.
Connect the amplifier turn on, power wire, ground wire, then RCA wires (in that order if you would like to, doesnt matter too much)
Connect your speaker wire you your amplifier, then connect it to your subs/speakers.
Check all connections, put everything in its place, reassemble the console. Make sure nothing is pinched.
Put the fuse in the fuse holder under the hood.
Enjoy your new subs/speakers. Just go easy on them for a few weeks, no loud music, or they will not break in properly.
(I cut and pasted some of that. I skimmed it pretty well, but I'm sure there are still a few things I disagree with in some of it, it's mostly basic information, and generally helpful though.)
there are 3 basic ways to kill a speaker: mechanical overload, thermal overload, thermal fatigue. power will not blow a speaker, whether too much or too little. you may feed a subwoofer any amount of power you wish. As a general rule, if you can't hear distortion, you will not blow the speaker.
unfortunately, even this is a misleading and fallacious statement. the bandpass box user will be delighted and crank the volume, hearing no distortion and thinking himself set. No relationship is made between the three methods of speaker destruction and power handling, such a discussion would most likely be too long and drawn out for a general bulleted tip list.
I dunno, I guess if I had to compress it down to a bullet, I would say something like: "power doesnt kill speakers, whether too much or too little. overuse of the gain know plus overuse of the volume **** kills speakers"
and again, its still not enough, it doesnt call for how much gain or volume! its a tricky one to bullet, I dont think I can come up with anything thatll be good.
Now, here's a few links that could also help some of the audio newbs...
First, here's my sound deadening FAq thread:
https://www.scionlife.com/forums/vie...ight=deadening
eCoustics- www.ecoustics.com Lots of information contained there, reviews, basic info, detailed info, forum, etc...
Basic Car Audio Electronics - http://www.bcae1.com/ - This site has it all. Everything you could ever ask is discussed here, but yet its extremely easy to understand here.(There's a bunch of links down the right side, navigate there, not on teh large left portion of the screen. It's a tan colored area)
Eddie Runner's site: http://www.installer.com/tech/index.html - Has some interesting articles about interesting stuff
Car Audio Usenet FAQ - http://www.mobileaudio.com/rac-faq/rac-faq_toc.html - Lots of basic information
Crossover Design Calculators - http://ccs.exl.info/calc_cr.html - For those that want to make their own passive crossovers
The Polyfill Article - http://www.win.net/audtatious/audio/fiber.html - Learn exactly how much box stuffing to use for your desired enclosure and what box stuffing really does for enclosures
Car Audio Forum - www.caraudioforum.com - Forum and chat room, chat room is owned and run by a friend of mine. Feel free to stop by and watch the freakshow
Elite Car Audio - www.elitecaraudio.com - Tightarsed high end audio junkies. They get annoying and stuck up on the forum, but they know their stuff quite well
Sound Illusions - www.soundillusions.net - Another good site
Port Tuning Calculator - http://www.2k4civic.com/portcalculator.html - A simple port tuning calculator that gives you a tuning frequency for a square or round ported box
Hopefully some of or all of that information helped you and maybe some other people on here understand some things they were having some trouble with.
Yeah, I know it's really long, but I still feel like it's worth the read, especially if you're just getting into car audio, or even if you've been into it for years. I'm sure there are people here that aren't going to learn anything, or aren't going to agree with everything. That's fine too, if you disagree, post so, and give reasoning. Sometimes the best way to a solution is to get opposing views to get the best possible answer. In my opinion, the information is accurate (to the best of my knowledge) and correct. Sure, I haven't skimmed it in a few days, so there's probably something I don't agree with in there, but it's probably minor information. I'll reskim it again in the near future adn edit it as I see fit. If you have something to add, or a question to ask me, feel free to post or PM me.
Without further adieu:
You get what you pay for?
the fact is, you don’t get what you pay for. not always. Its a problematic statement, especially with the overuse of the term "90% install, 10% equipment." Its a poor statement as well, but it really does apply to this situation.
lets compare. You just purchased DLS 3" wide range speakers which you’ve installed into your a pillars. I just purchased JL VR coaxials which I just put into my doors. our cars are otherwise identical in every other way.
you bought high end 3's and paid twice as much as I did for my entry level coaxials. who got better sound?
well, if we start getting random members to sit in our cars, the very VERY first thing they will notice is the lack of low frequency extension in your car. assuming we don’t have subwoofers, or even if we do, bass guitar will simply be more impressive in my car than yours. That alone will get me more votes for my car than you.
next thing to notice will be the top end. You will probably have some problems with your top octave. my VR tweeters wont have too many problems at least getting parts of the top octave. they might say I have brighter highs or something, or have to be told, but I will probably still get more votes than your car, though it will be closer.
the final problem will be actual location. this will require members who understand a thing or two about sound stage. when they sit in our cars, the first thing they will notice is my car has an image. center is within reasonable location, at a decent height. distribution will be kind of off, but again, we aren’t arguing perfection at this point, merely which "sounds better." When we sit in your car, we will notice that we hear whichever speaker is closer to us (driver OR passenger) and it will be so overpowering that it will sound louder than the other side, and phase will make some voices like center sound like there are two. I'm hearing double!
when it came down to money, You spent about twice as much on your soundstage than I did. yet my car outperforms yours in every way, shape, and form.
it becomes a tricky situation when we take into account that most members here aren’t going to be comparing installs, and that they will just be thinking about what door speaker will sound best. in the door. period. But, even here, its not quite so concrete as more money is better! those kodas at $80 each will yield much better off axis performance and higher low frequency extension than, say, digital designs midranges. practicality also enters into the setup, as those same DD speakers are over 3 inches deep!
and that even tang band speakers wont easily fit into the doors, despite having neodymium magnets.
Finally, threes always the ebay/forum phenomenon. say I stumble on a gentleman who happens to be selling his scanspeak revelator's for $200 the pair, he was just feeling REALLY nice. guess who's car is going to absolutely thrash any other in here who is also running $200 worth of midrange?
so, I don’t really think that you do get what you pay for.
Lacking Midbass?
the issue lacking midbass is something that should probably be out in the open, but the way its worded doesn’t work very well. many speakers are available that output plenty of Midas even at a very reasonable price. JL VR coaxials are one of them. I don’t see them often in cars. infinity reference, cdt classics, I see very, very often. why? they are in a group of a great many entry level speakers that don’t have basically any midbass capabilities at all. so yes, I can definitely see why we could use a tip that lets people know to expect a drop in midbass performance at the cost of improved volume capability for cheap upgrades.
but this isn’t to say that we cant choose speakers that can match the stock frequency response performance! we can reasonably easily find a great many speakers that have both enhanced volume and enhanced low frequency extension, as long as we aren’t shopping in the $30 speaker category! and even then there are a few models, if one looks hard enough!
I don’t see the relationship though, with being able to take more power and having less low frequency extension. I'll cheat with this example, and say what about your subwoofers? increased power handling AND increased LFE!
but seriously, we can stick with 6 inch speakers. what about those JL VR's? what about the XR's? what about adire kodas? what about kicker cmb is it? and what about the speakers that can get pretty close to as low as the stocks, if not well exceeding them? like DD w6's, peerless csc's, image dynamics chameleons? we can even cheat, and look at tang band 6's or JL w0's. talk about low frequency extension!
Amps adding/enhancing LFE?
I don’t see an amplifier enhancing LFE. you are stuck with the low frequency performance of whatever driver you buy. if you buy a 6.5" that only plays to 100 Hz, till play to 100 off deck power, till do that off an amp.
in fact, threes some evidence to suggest aping your speakers might DECREASE bass performance! as the gain goes up you'll be more likely to have problems with your bottom end, and be forced to have bad sound at high volume, or up the highpass filter cutoff frequency.
now, component sets sound best when accompanied by subwoofers? to use the term "component set" in this way is to suggest a component set works with a subwoofer better than a coaxial works with a sub! we can make many, many, many potential equipment combinations with both component sets and coaxials that are good and bad both! So it cant be that.
or was the statement intended to say that the speakers in front in the car work best with a subwoofer? again, simply not true! will it be better? probably. my mother sure wouldn’t agree! neither does my girlfriend!
the term "bass" is very difficult to discuss, especially when bridging a discussion between midrange drivers and sub-bass drivers. 100 and below? 50-150 Hz? is it a system we are trying to maximize low frequency extension up front, or do we not care, and use 8 inch subwoofers in he back playing up to 200 Hz, so long as we get all octaves covered? It makes things more difficult.
regardless, I try to use relative terms, so no one gets confused. thus, the bottom end of 6.5 inch speakers becomes low frequency extension. the very very bottom octave of subwoofers becomes low frequency extension, too. in terms of frequency values, the same frequencies for 6.5 lfe becomes subwoofer top end, etc. and that even changes based on size.
but the relative discussion makes for absolutely ZERO confusion when someone tells someone else "yeah, these speakers have a lot of bass". then based on that tip, someone makes a purchase and is ____ed his speakers don’t play low at all!
Soldering Connections, and RCA’s
There’s no way I can advocate solder to make connections. the name of the game in a car is "preserve the value of the vehicle", not "make the best connection that’s humanly possible". there’s a reason that the vast VAST majority of high end shops out there use t-taps rather than solder, and its not entirely speed! Its far more important to have a high resale value on the car five years from now than a connection that will last forty years rather than twenty years! if your taps are falling off after two weeks, its not a sign you need to solder, its a sign you should be working harder on making a solid tap!
cables themselves. there is no way I can advocate buying kimber cables over radioshack gold series every time. noise floor in a car is ridiculous as it is, but even with the car off, in a quiet neighborhood, I get ZERO noise in my own car. I don t have kimber, I have el-cheapo!
now, I can definitely see instances when high end cabling would be needed. I was routing some RCA's in my car in a previous install right across the fuel pump. got some noise! throw in a higher shielded cable, and everything was fine. does that mean I needed to buy $70 rca cables to get from the radio to the rear seats? no way!
as for the connections, its all about long term reliability, and nothing else. are you gonna unplug your RCA's three times a day? will they be tweaked this way and that, will there be pressure on them by a trim piece, or when stuff gets thrown into your car? you’d be a fool to buy radioshack cabling! My own amplifiers are in their own designated areas, foreign objects cant access them, and I don’t tug on the cables. why should I buy cables with burly and bulky ends?
as to those cables themselves, I was doing a mustang a couple years ago. we had two cables in the car, monster and audiopipe. the monster turned out to be noisy as heck! they were routed in the SAME spot, and the monster cable induced more noise than the audiopipe! haws that for high end! so sometimes, a cheaper cable can really be the better one from a noise perspective!
as for the head durability problem, another friend and a ford ranger, with knu top end rca cabling. Every time we unplug the cables, the heads start to unscrew! talk about annoying! if he bought the uber UBER cheap cables from radioshack, he wouldn’t have problems with the heads coming unscrewed! not that I am advocating the ultra cheaps in this case, I think he would have had a great deal of problems with noise and connection reliability with kids crawling around the back of the truck to have radioshack rca back there, but when you are paying triple digit numbers JUST for rca cables, there is NO reason I should have to threadlock the heads on!
so what IS better? radioshack? monster? kimber? audiopipe? well, I think its gotta be application based with a heavy emphasis on budget. It definitely surpasses the help a one sentence tip could give on the matter, unless that tip said "when in doubt, let your budget do the talking"!
Dynamat Prevents Rattle?
I think its a very good idea to be promoting the fact the dynamat will probably not prevent rattles. But absorb vibrations? Imp pretty sure most of dynamat if not all is the type that merely raises panel resonance to prevent ULF (ultra low frequency) waves from causing resonance issues. regardless, a tip thread should be unimpeachable.
but lets not forget ALL the applications if we are going to say it cleans bass and makes bass louder! we use it to eliminate road noise, engine noise, raise bass efficiency, seal doors better than stock, etc, etc, etc! It might be better to leave the rest of the practical apps of dynamat entirely out of the tip thread, a tip thread is to give practical advice on how to act in a certain way as a reference.
thus "dynamat is not designed to prevent rattles" is probably a sufficient tip.
but here's the ultimate in offensive results of dynamat use. Ever install dynamat extreme behind your door speakers? reflections off the aluminum plate often causes cone interference and make your sound FAR worse! But those who were willing to spend $40 or more on those small pieces of mat and then thought their performance increased would be offended if we insulted that use of money.
Bass, truly omni directional?
I wish bass were omni directional, but its not. its a simple test though. put your HT subwoofer on the right side of your room. when something explodes on screen, does it explode on the screen, or does it explode off to the right?
same thing in the car. all my sub-bass comes from behind me. I wish bass were omni directional, I could put subwoofers in the trunk and they would sound like they are on my hood! But I have to live with bass coming from behind me.
Fire Direction relates to response?
we can load the subwoofers off the rear deck, we can down fire, side fire, put them into the cabin, even mold them into the dash! its redundant and unnecessary information to discuss rear and forward firing exclusively here, especially when its incomplete just discussing those two topics, much less including all others. eddie runner spent more time discussing box facings than I have in this thread all together. its a complex subject!
different subwoofers, boxes, and firing positions will provide different bass performance results. not better, not worse. different for different desired effects/applications.
Capacitors?
People saying that caps help keep voltage constant around 14.4 V, etc. I'm sick of reading stuff like "get a cap, it'll help blah, blah, blah..." The following information is excerpted from CarSound's great cap debate thread, or whatever they choose to call it. The excerpted portion that I am pasting here is all information posted by Richard Clark, whom is a moderator there, and one of the godfathers of car audio. He even offers $5,000 for anyone that can disprove him, but the catch is you have to have factual scientific data to prove it. There are several books that both he and Dave Navone co-authored about car audio, and have the data included. I'm sure there is a PDF somewhere as well, but this is a long read of information that proves the "theorys" related to cap functions incorrect, and untrue. Read through the whole thing, and gain an understanding of caps, and their use, and what they actually do before trying to debate this information. If you have a dispute with it, perhaps you should contact Mr. Clark. Caps do nothing except possibly, not defiantly, possibly help dimming. They aren’t guaranteed cures for voltage problems/lacking voltage/falling voltage, etc…
Lesson 1
Ok “powertrip” how about we have a discussion in basic electrical theory? At the end of this thread you should be the one that can explain to the world that according to ohms law it is impossible for these things to do any good. That is of course if you can admit that they do obey ohms law. We will do this a little at a time so how about you humor me and stick to my questions. We will do them a couple at a time so everyone can follow along. Let’s do a little calculation. Suppose we have a resistor that is .017 ohms (seventeen milliohms). I think that is what you say the ESR of the giant caps is.
The ones I have seen have measured higher but I will give you the benefit of the doubt. According to ohms law how many volts are dropped across .017 ohms if 100 amps of current are flowing? How about if we up the current to 300 amps? Let’s establish the answers to these questions before we go any farther. If we can't agree on the answer to this there is no hope we will ever get to the truth.
Lesson 2
Thanks David you are exactly right. If anyone wants this explained please ask David to clarify it. If everyone is going to follow this and understand fully the final conclusion it is important that no one miss any steps. There will be about ten lessons. Since power trip has left the building we will continue with the rest of the class. ESR stands for equivalent series resistance. This means exactly what it sounds like. It means that if we have a source of voltage it will behave exactly as if it has a resistor of the same value in series with its output. An amplifier has ESR, a power supply has ESR, a battery has ESR, and yes, a cap has ESR. Components have ESR’s because we do not have perfect conductors to make things from.
And now for the homework. Last night we learned that if 100 amps flows through .017 ohms there will be a voltage drop of 1.7 volts. And if the amp flow increases to 300 amps the voltage drop will increase to 5.1 volts.
For the sake of theory only let’s say we have built the largest cap in the universe and it has billions and billions of Farads. Its plates are made of a newly discovered material we'll call unobtanium. This new material has no resistance therefore our super cap has an ESR of ZERO ohms. We then charge the capacitor to 14.2 volts. We then place a resistor with a value of .017 ohms in series with one of the terminals of this cap. The question is: If we place a load that draws 100 amps from this cap what will the resulting voltage be on the load side of the resistor? What will the voltage be on the cap side of the resistor? What about if we increase the load to 300 amps? What will the voltages be on each side of the resistor?
Lesson 3
Ok now that we have studied ESR and understand what it is and it’s effect on the working of a circuit we will move on to another subject. But don’t forget about ESR as it is one of the important final building blocks in our search for truth about caps and we will come back to it. Today we will review the important concepts about total energy storage in a device like a cap. This has been covered in earlier posts (and I will say quite correctly) but I am going to expand on it as well as reiterate it for those who did not get to read it. Besides, I think I can simplify it a little.
In electronics, we measure power in watts. Wattage tells us how much work a device can do. But a wattage rating does not tell us anything about how long we can sustain that work. When we add the element of time to our wattage, we use a value we call Joules. A joule is a watt second. This means that one Joule of energy can provide a watt for a second. Ten joules can provide a watt for ten seconds or ten watts for one second or five watts for two seconds one hundred watts for a tenth of a second, and so on.
The formula for determining the total joules stored in a capacitor is very simple. We take one half the capacitor’s value in farads and multiply it times the squared charge voltage. For example a one farad cap charged to 14 volts would be .5 X (14x14) = 98 or .5 X 196 = 98 Joules. A 20 farad cap charged to 14 volts would be 10 X (14x14) = 1960 Joules.
There is a very important concept to understand about energy storage. A capacitor actually stores electricity.
Batteries don’t. Batteries have the potential to produce electricity by means of a chemical reaction but caps actually store electrons on their plates in the form of an electrostatic charge. In our next two lessons we will learn why this is important to know.
But first, the homework. This is a “think about it question”. We have learned that a Joule is a watt second. A Yellow top battery is rated at 65 amp hours. This means it can provide 65 amps for an hour. The question is how many Joules does this represent? Since this is a thought question, it would really help if whoever answers would show us your math.
Lesson 4
In the actual real world the voltage of the battery would drop a little from its open circuit voltage of 12.8 volts with a 65 amp load. In the case of the yellow top its actual voltage at 65 amps is about 12.2v when fully charged. By the end of the hour it would be down to about 10v. If we use 11 as an average our answer would be........ 2,574,000. Now that's still a lot of joules! Now actually this is not enough to totally kill the battery but at this point there isn't much left in it. This brings us to a very important fact. The energy in a battery will be depleted almost completely by the time it is down to 10 volts.
Lesson 4 (continued)
By the time we have removed those 2.5 million joules from the battery it probably doesn't have more than a hundred thousand joules left. We can almost totally deplete the battery's energy and never drop below 10 volts. This is because the battery doesn't store electricity. It stores chemicals. A chemical reaction produces the electricity. Storing actual electrical charges is very inefficient.
Look at our poor capacitor. Even if we made one as big as a battery it would still only be good for perhaps fifty to one hundred thousand joules---less than that left in a nearly dead battery. But if that were not enough there's more bad news. This exercise will be tonight’s homework.
A capacitor is like a gas tank in a car. The pump can only remove gas down to the pickup point. Any gas below this point can never be removed by the pump. If we charge a 20 farad cap to 14 volts we know from previous lessons that it will contain 1,960 joules. If we use that cap in a system and load it till it drops to 10 volts along with our battery how many joules will we have removed from the cap? How many joules will remain in the cap that we can never benefit from if our system never drops below 10 volts?
Lesson 5
In our last lesson we learned that caps actually store charges on their plates. And of the 1960 joules stored in a 20 Farad cap, 1000 of them sit at a potential below 10 volts. This means there is no way they can ever be used by an operational audio system. Today we will look at another loss factor. It has to do with the loss factor due to the ESR of the cap.
We have already studied voltage drop due to ESR but now let’s view it from an energy/watts standpoint. Let’s clarify things. The power delivered to the stereo by the battery and alternator bypass the cap. They merely flow by its terminals. If the cap charge is lower than the battery/alternator potential current will flow INTO the cap until it reaches equilibrium with the Battery/Alternator. If the B/A potential is lower than the charge potential of the cap current will flow OUT of the cap to the battery and or the amp.
Always remember that voltage always flows from the highest potential to the lowest potential, just like water. Current does not however flow into the alternator even if it is lower than the battery and cap because it has diodes on its output that only let current flow FROM its output. Now whenever any current flows into or out of the cap it must pass thru the ESR of the cap. The resistance is really distributed throughout the cap but it behaves just like it was right on the output terminal as in a series circuit location in the circuit loop does not matter. Now suppose our 20 farad cap is charged to 14.2 volts and we place a load on its output. This load is the same one that we used in lesson 2 to cause 100 amps of current to flow from our unlimited capacity cap. Only now we have our smaller 20 farad cap.
Lesson 5 (continued)
We know that if 100 amps of current flows out of our cap, those 1.7 volts will drop across the ESR of .017 ohm. This will cause the output to drop to 12.5 volts just like it did with the unlimited cap.
This means that the load (100 ohms resistance) will be consuming 1250 watts from our cap. 12.5 volts x 100amps = 1250 watts. The total wattage output produced by the cap is 1420 watts. 14.2 volts x 100 amps = 1420 watts. Unfortunately 170 watts of power will be lost in heat in the ESR of the cap. This represents a loss of 13% of our total usable joules (960) at this point. Now tonight’s question is if we increase the current draw to 300 amps (300amps x 14.2volts = 4260 watts), how many watts will be dissipated in the ESR of the cap and what percentage of the total 4260 watts does it represent? Of our total usable 960 joules, what percentage will be left for the stereo?
Lesson 6
Ok before the next lesson let’s review lesson five. When I checked the posts no one had the correct answer of 56% but some were close. The important part is that everyone seems to understand the loss mechanism. From lesson five we see that the energy we can get out of a cap is inversely proportional to the rate that we try to take it out. This is because the ESR that is in series with the output stays constant regardless of the load. At very high power levels, this ESR can amount to a sizeable amount.
In an earlier lesson we learned that the ESR causes a voltage drop proportional to current flow. When voltage is dropped across a resistance heat is created. Lesson five taught us that with 100 amps (flowing from a cap with .017 ohm ESR) we lose 13% of our joules as heat when we try to remove them. If a cap has an ESR of .017 ohms, and 300 amps flows we will lose 56% of the stored energy when we try to remove it. In our giant cap example with 300 amps of current, we will lose this as 1530 watts of heat. This is the same loss mechanism that causes a battery or amp or power supply to get hot when they are delivering high power levels. Virtually all voltage sources have at least some ESR. At this point we should have a good understanding of how ESR affects a component. The next logical thing to cover is ESL.
ESL stands for equivalent series inductance. Just like the ESR it can be modeled as an inductor in series with the output of our capacitor. Now everyone in car audio knows what inductors do. They resist a change in current flow. Their most common use is in speaker crossovers. When used in series with a woofer they let the slowly changing low frequencies pass, but stop the fast changing high frequencies. The reason an inductor does this is because it behaves like a resistor that changes value with frequency. Unlike a capacitor that decreases in value with increasing frequency an inductor decreases in value with decreasing frequency.
Lesson 6 (continued)
Now I have been told that the ESL value of the giant cap is 0.2 mh. Somebody check my math but I think this would put the reactance of the cap near .063 ohms at 50 Hz. This means that if we wanted to refresh our amps at a rate of 50 Hz (seems reasonable if we were playing bass real loud) our ESL of .07 ohm would be in series with our .017 ohm ESR for a total value of .08 ohms.
Now we know from ohms law that if we try to get 100 amps through .08 ohms we will have a voltage drop of 8 volts and at 300 amps the drop would be about….well it’s pretty clear that we will be left with less than a fraction of a volt if we start out with only 14.2. Is everybody still with me? I know it’s not good news but I’m not making this stuff up.
Now for tonight’s lab lesson to prepare us for lesson 7. Tomorrow, I will post the results of the following test. If you want to check me, go to Radio Shack and buy the following: Bulb # 272-1127, Socket # 272-360, and a nine volt alkaline battery. For the battery a Radio Shack is ok but a Duracell is better. Make sure it is fresh!!!!!
Wire the socket and connect it to the nine volt battery and record how long the bulb stays lit. Be prepared to wait for a couple hours. Charge a giant cap to 14.2 volts and do the same with it. Be prepared to wait about an hour. Charge a 1 or 1.5 Farad cap to 14.2 volts and do the same. This will take only a few minutes. Record the times and we will discuss the importance of this in our next lesson.
Lesson 7
Ok in last lesson I left everyone with instructions to duplicate the results of the test I am going to post tonight. The purpose of this test was to put the capacity of even a giant cap in perspective. As I have pointed out in earlier lessons storing electrons in the form of a charge on a plate is not really very efficient. Some folks think we should stand in awe of a value like 2000 Joules. Well our test tonight puts some reality in this value. If we perform a test like described in the end of lesson 6 we come up with the following results.
1.5 Farad cap lights the bulb for about …………5 minutes and 28 seconds
a giant cap lights the bulb for about……………. 54 minutes
a nine volt alkaline does so about …………………. 2 hours and 14 minutes
did anybody get results similar to these…….are we in agreement on these numbers ?
Lesson 7 (continued)
As for the relationship of these numbers, each of these units has a higher ESR than the previous one. The highest ESR in the group was the nine volt battery. It actually has enough energy to light the bulb far longer but since its ESR is fairly high it loses a lot of its energy as heat internally. But even still it should be apparent that it holds more energy than the giant cap and a whole lot more than a 1.5 farad unit
For now I do not care to concern ourselves with the meaning of this ---we will cover it in the closing. Before going on let’s review a few facts. In lesson 3 we learned that a giant cap can hold 1960 joules at 14 volts. In lesson 4 we learned that only 960 of them sit at a potential above 10 volts. In lesson 5 we learned that if we want to use them at a rate of 100 amps we will lose 13% of the 960 that are left.
If we use them at a rate of 300 amps we will lose 56% of the 960 which will leave us with only about 500 usable joules. And these losses are only for the ESR mechanisms—they do not include the ESL mechanisms that could actually be higher if the demands are quick enough.
It has been suggested that the purpose of these giant caps is to provide quick energy. It has also been suggested that they are for slow energy.
I am not sure what is being claimed so I guess I need to cover both situations. As for slow energy I think the previous test could put that thought out to pasture. For long term energy one of these units is less useful than a nine volt battery and to compare it to a car battery is really useless. After all what good is 500 useable joules when we have over 2 million in the car battery? It should be obvious if one of these devices can be of any use at all it will have to be able to provide energy faster than a car battery. But before we get to that issue lets cover the behavior of alternators and batteries under dynamic load conditions.
Tomorrow is Saturday and I will have time to measure the response time of a few alternators. This will enable me to model my closing explanations more exactly. I will post the results of these tests tomorrow night.
Lesson 8
For this lesson I have done some actual measurements. Here are the test conditions: To measure voltage we used an Audio Precision with a DCX module. It is accurate to three decimal places. For sample time we chose 40 samples per second. For the non audio system test I used a KAL carbon pile load tester. It can do power tests on 12 volt charging systems up to 1200amps continuous. The audio system consisted of a couple of Rockford 1100 amps bridged into four ohm nominal speakers. The alternator was a stock Delco 80 amp CS type unit.
Lesson 5 (continued)
Its case temperature was monitored by a Raytek ST2L IR sensor. Engine speed was regulated with a Thexton #398 IACV tester. The music material was the SPL track # 30 from the IASCA competition disc. The battery was a Stinger spb-1000. All voltage measurements were done directly at the terminals of one of the amps.
Chart 1 Alternator/cap/battery test with 200 amp dummy load
For this test we monitored the voltage of the car with the stereo turned off. With the car running the voltage can be seen to be stable at about 13.7 volts. After 22 seconds (The horizontal scale is 100 seconds-10 sec per major division) we applied a 200 amp load. The voltage can be seen to drop to 11.6 on both traces. This test obviously exceeds the ability of the alternator to keep its regulation set point so its voltage falls. The drop can be seen to be nearly instant (steep curve) until about 12.5 volts where the battery starts to supply a significant amount of the power.
Ultimately the voltage drops to 11.6 and at 26 seconds we turn off the load. The voltage then starts to rise to the regulator set point as the battery is recharged (yellow curve) and as the battery and cap (green curve) are recharged. At a time of 50 seconds I turn the motor off so the alternator stops. The voltage then droops down to the float voltage of the battery—about 12.7. The only reason for the small difference at 50 seconds is because I couldn’t get the timing of the engine shut-off exactly the same every time. I did it several times and these two are within one second. That was as close as I could get it.
I am able to see no difference from these measurements. There are microscopic differences but I believe they are due to the alternator temperature. Alternator regulators are usually temperature sensitive. As they get hotter they tend to fold back. For this reason we let the unit cool off between each test and closely monitored the case temp throughout the tests. For this reason I believe that none of these measurements are meaningful to more than a couple tenths of a volt.
Chart 2 Music tests with an audio system
Note: Between each test the alternator was allowed to cool and the battery was charged until an automatic charger said it was topped off.
Purple curve
For our first test we played the system with the engine off and no cap. The result was the purple trace at the bottom. We played the system as loud as we could get it that seemed to produce no audible distortion. This was track 30 of the IASCA disc. It starts off with fairly low level sounds for the first 34 seconds. In order to insure the electrical system was stable we did not start the measurement until we were 20 seconds into the song. This means that our 0 starting point is: 20 on the CD counter. The battery was able to maintain its voltage just below 12.5 until the loud bass hits at 34 seconds (14 seconds into our chart) At this time it dropped to about 11.5 and had a few large variations due to the music. According to the computer calculations (third chart) the average voltage for this test was 11.7volts. This test was done as a baseline for the following tests.
Yellow curve—no cap
For this test the volume was left as it was for the baseline test. The engine was started. Notice that at low volume the alternator was able to maintain about 14 volts. When the loud music hit the voltage dropped to about 12.5 where it remained except for a few short moments where it actually climbed back to over 13.5 volts. The computer averaged calculations for the average voltage during the 100 seconds of this test was 12.973 volts.
Red curve—cap added
This test was identical to the previous test except the cap (15 farad type) was added 6 inches from the amp with 4 gauge wire—no relays or fuses. The red curve seems to overlay the yellow except that the actual peaks don’t rise as fast or as high during the brief quiet moments. I feel this would be due to the alternator having to recharge the cap. The voltage on loud passages hovered around 12.5 volts. The computer averaged calculations for this test show the average voltage to be 12.878 volts. I see no meaningful differences with or without the cap. I certainly don’t see the voltage sitting solid at 14 volts.
One note I might add is that this was a two thousand watt system driven right to clipping and the average voltage stayed above 12.8 with a stock 80 amp alternator. Under these conditions the battery would never discharge!
The green and blue curves were done just for kicks while we had the system set up. In both these tests we turned the volume up until the system was very distorted. This placed a severe load on the alternator and caused the voltage to dip as low as 12 volts. The curves seem to follow each other so closely that unless you have a good monitor it is doubtful you can tell there are two curves. The average voltage for these two curves was both 12.277 and 12.295 volts. If this volume were sustained for very long periods of time this battery would discharge.
Any questions? Please ask -- I will give everyone a chance to ask them before I sum this all up in lesson 9.
Lesson 9
Now that we have had time to study theory in each of the 8 lessons and the results of the actual tests on a real system it is finally time to bring this discussion to a close. Unfortunately, when this thread started I was unable to explain the concept, as it was obvious that many of the people posting responses just didn’t have a good grasp of the way things really work. Those of you who have taken the time to follow the lessons should know by now why I was so frustrated at the arguments that were so illogical. It is important to keep in mind that this is a technical forum, not a marketing forum. I do not care or want to know about companies or brand names.
Nothing I have said was ever meant to disparage a particular product or company and I would appreciate it if in the future we could always keep that in mind. We should be able to discuss the merits of radial vs. bias ply tires without caring if they are made by Michelin or Goodyear.
In car audio we have little choice of how we are going to power our systems. Presently we have only four things that are practical. Each of them has its own characteristics that incorporate good points and bad points.
Let’s review them
The battery--this device has the ability to provide a very large amount of current. But due to its nature the current is provided at a voltage that is less than optimum –at least for a high powered stereo. Since its float point is 12.8 volts if fully charged, it can provide current only at voltages that are proportionally lower than 12.8 Volts.
The alternator—this device is electronically regulated at a point that allows it to recharge the battery. The alternator is usually designed to output voltage in the 13.8 to 14.5 volt range. Because its output is actively regulated it attempts to maintain this voltage with varying load conditions up to the point where it’s output cannot keep up with the load at which time it’s output drops off very rapidly. While relatively tight regulation is the strong point of the alternator it’s weak point is that it simply is not practical to obtain one that can provide large amounts of current like a battery is capable of.
The capacitor. The advantages of a cap are that it can charge up to whatever the highest voltage source in the system is, (in a car this would be the alternator) and provide current at this elevated voltage. The down side of a cap is that it cannot store very much total energy and only a portion of this energy is available at a usable voltage potential. The fourth type of device is an electronic voltage regulator. These devices have not been part of this discussion so I will pass over them for now.
Now modern car audio amplifiers are capable of consuming enormous amounts of power. Even with efficiencies in the range of 60% to 90% an audio system is capable of drawing hundreds or thousands of amps from the cars electrical system. Typically, the audio system is larger than any other electrical device in the car including the engine starter. Fortunately for the car, the demands of an audio system are rarely continuous in nature. The very nature of music rarely demands more than a duty cycle of 10% to 20% from a power standpoint. This means that the audio system is demanding short term, but repetitive peaks of current from the electrical system.
The primary source of this power is the alternator. It should be considered primary for two reasons. The alternator is the only first generation source of power. It ultimately provides all the power for the system either directly or indirectly by restoring power to the battery or cap. It is also primary as it is the power source with the highest voltage potential. In an electrical system current always flows from the source of highest voltage to circuits of lower of lower potential.
All three devices can be used in a system to great advantage. But the dynamic conditions present in a music system determine the role each device plays and to what degree. To understand this lets consider a low current drain condition. In this scenario the alternator will be at or near its set point.
This voltage is designed to be high enough to charge the battery meaning it will be one or two volts above 12.8 volts. This means that the battery will actually be a continuous load on the alternator and provides no power to the system. The size of load it presents is determined by the state of charge of the battery. The higher its state of charge the smaller the load will be. A cap if present in a system in this state will present a load for a finite amount of time until its charge voltage reaches equilibrium with the alternator.
Unlike the battery, the cap will cease to be a load after it is charged except for a factor known as dissipation, which for all practical purposes can be ignored in this application unless it is excessive. Under these circumstances, as long as the alternator can maintain its set point, it will provide all the power for the music system and the rest of the cars accessories. The battery and cap may as well not even be in the car.
Now if we increase the current demands of the music system to an amount that taxes the alternator its output voltage will begin to drop. Even so the alternator will continue to be a source of current to the system –i.e., the car, music system, and battery. It is at this time that the cap will begin to discharge and begin to augment the alternator as a source of current. The degree to which it provides current to the system is dependent on the actual voltage at the alternators terminals. Only when the alternator begins to drop below the caps charge potential does current flow out of the cap.
This is a continuous process and the current provided by the cap tries to maintain the voltage at its charge potential. The degree to which it can do this is dependent on two things. The current provided by the cap is limited to the total capacity of the cap and any series reactance’s (resistive or inductive components) that are part of the cap. The instant the cap starts to output current its charge potential begins to drop.
Now just what can we expect the cap to provide? Suppose we happened to have a cap charged to 14 volts, with a total reactance (made up of either resistive or inductive components) of about .017 ohm. We could figure that at the first instant of discharge it could provide ten amps at 13.83 volts. Of course if we were playing the system at a level enough to load our alternator, ten amps is not likely to provide much relief. But perhaps 30 amps might help—at this modest level our cap could begin to provide current at a potential of 13.5 volts. (lesson 2).
Of course this voltage level would drop at an exponential rate commensurate with the discharge curve that is standard with caps. No doubt the cap could help out a hundred amp alternator with the addition of an extra 30 amps even though it might be for only a brief instant. But it is sort of interesting that at even this modest power level of 130 amps (100 amps alternator + 30 amps cap) the cap is unable to maintain the voltage at 14 volts.
Of course in this scenario we are sitting at 13.5 volts for a brief instant and our poor battery is unable to help at all as its potential is at a lowly 12.8 volts. In fact the battery is still a load on the system!
Now what if we get serious with our stereo and we really crank it up? Lets say we have something like a manufacturers demo van with lots of amplifiers that can draw hundreds of amps on musical peaks. Lets pick a nice round number like 500 (“Cade” said 490) amps. Lets say we have a 200 (“Cade” said 190) amp alternator. Typically such an alternator can maintain a voltage near its set point up to perhaps 80% of its rating-after which its voltage begins to drop as it provides large amounts of current. As I am not familiar with all the different alternators lets just assume these assumptions are close and our alternator is putting out 200 amps. Well our amplifiers in an instant are asking for 500 amps so what happens?
In any constant voltage system when the current capability is exceeded the voltage drops. So let’s say our alternator voltage starts dropping. What does our cap do? Since its charge potential is at 14 volts it starts to discharge and provide a source of current. Since the cap is now sharing the load with the alternator it is called on to provide what the alternator can’t—that would be 300 (see footnote) amps.
What happens to the terminal voltage of our cap when 300amps is flowing? Well for starters, the voltage tries to drop nearly 5 volts inside the cap before it can even get out. Not in a short time but instantly. There is no time constant in the formulas for ohms law. They are instantaneous calculations! But wait. The voltage doesn’t really drop to 9 volts because we have our battery sitting in reserve waiting at 12.8 volts.
Our cap lets our poor alternator down as the voltage plummets and when things hit 12.8 volts our battery jumps in and starts to take over. The battery with its enormous storehouse begins to provide vast amounts of current until things lighten up for our poor cap and alternator. Of course we could add another cap to halve our ESR loss to only 2.5 volts but that would still cause the cap terminal voltage to drop to 11.5 volts.
Let’s see how many caps of this spec we would have to add to keep the voltage at 13.5 for even a few milliseconds. We would need a cap bank with a total ESL of about .001 ohm. Gee it looks like it would take over thirty caps paralleled to maintain 13.5 volts at 300 amps for even a brief instant. And let’s hope we don’t need to do this for long, as the total power contained in thirty units is only about what is in a dozen 9v alkaline batteries! (lesson 7)
It should be clear that if the voltage doesn’t drop the caps don’t do anything. The voltage MUST drop for them to start discharging.
Now, is it possible to have a steady 14 V because we added caps? I don’t think so.
When considering a replacement for your stock speakers please realize that they are designed to output bass, mid bass, AND highs. If you replace the speakers with something else and they take alot more power, you will most likely end up with much less bass and mid bass.
If you replace the stock speakers with a component set you will get mostly mid bass and highs. If you use an external amplifier it will be a little better for bass, but component sets sound best when you accompany them with subwoofers.
Make quality connections or nothing will work right or for very long. Use Gold/Platinum ends if possible.
Don't skimp on connections.
Dynamat DOES NOT STOP RATTLES. It absorbs vibrations which will (long story short) clear up the sound and make your speakers/subwoofers louder.
Subwoofers / Amplifiers
Human hearing is 20Hz - 20,000Hz. Anything over 20,000Hz you will not hear. Anything under 20Hz you will feel but not hear.
When matching an amp with a sub or a speaker to an amplifier/Head Unit, make sure the RMS rating on the amp is less than or equal to that of the sub, for that impedence (ohm rating).
As a general rule the best mix of SPL and SQ for subwoofers will be in a box built to the specifications of the subwoofer company for that specific sub.
Keep in mind the wattage ratings on amplifiers are usually at 14.4 volts or close. This means if it draws alot of power and the voltage drops to 12 then the amplifier will not be outputting as much power. The only amplifiers that combat this effect are ones featuring a "Regulated Power Supply" like the JL Audio Slash series
When tuning an amplifier do not turn the gain way up or put large amounts of bass boost on;
Clipping is when the shape of the sound wave becomes less round and more square.
You may safely give the subwoofer or speaker less power than it can take, but make sure you do not get distortiona and clip the signal
It is also possible to give a subwoofer much more power than is recommended but at this point it is much more sensitive to distortion and will blow much much easier. If you do not know about this already then do not overpower or underpower you speakers or subwoofers! (Or get professional help)
Make sure your fuse is the right rating!!! Too much and it will let your amp kill itself. Too little and the fuse will blow all the time.
When adding/moving a battery to the trunk make sure it is in a sealed enclosure. Your body does not act well to toxic gases.
Make sure you use a large enough wire (smaller gauge) to carry power and to ground. If the wires are too small they will hold back your system and could possibly overheat and melt.
Head Units
For most cars you will need a mounting bracket to mount an aftermarket stereo because the stock stereo is not a regular size or shape.
Most recievers are DIN or Double-DIN sized. Almost all mounting brackets accept DIN sized stereos, but there are a select few Double DIN kits for our cars.
A regular CD will hold about 20-25 songs. An MP3 cd can hold 256 songs. Make sure you get a CD player with MP3 support even if you do not plan on using it. You will thank me later.
Some recievers support WMA also, which is like an MP3 but compressed differently. If you rip music using Windows Media Player you NEED WMA support!
Many recievers are Satellite radio ready, so if you use Sirius or XM get a head unit that can control the reciever instead of having 2 things to worry about
Don't use the loud, Magna Bass, or other stupid functions on your reciever. They just distort the sound and can cause harm to your speakers and subwoofers (to an extent)
The more band the EQ is the more control over sound quality and sound shaping you will have.
Preamp outs are necessary for decent subwoofer performance unless you are going to use a quality line converter.
In Dash DVD
It is only illegal to have a screen that the driver can see if it has motion (ie movies, etc)
A screen of text is not illegal even when moving.
It is illegal to have an in dash DVD player wired to be able to watch movies while driving if the screen is in view of the driver.
Most units have a seperate brain box that is quite large and must be mounted outside of the area of the reciever with the screen. If you dont want to mount a seperate box look at the select few that do not have them (VRX745VD now re-released by clarion as VRX755VD with a few new features)
Wiring an Amplifier
The first thing you should do is purchase a pre-assembled amplifier wiring kit if you are not very knowlegable and experienced in this.
Start with the power wire; Connect the + power wire, with NO fuse in the fuse holder, to the + terminal on the battery. MAKE SURE THE FUSE IS WITHIN 12 INCHES OF THE BATTERY!!! I CANNOT STRESS THIS ENOUGH!
Next run the power wire along the other wires going down toward the passenger side fire wall. Use Zip Ties to secure the wire along other wires, this way there is no chance of it ever getting cut or damaged. To get the wire to the trunk you may do one of 2 things. First you could take out the seat on that side, and run the wire completly under the carpet, which will end up coming out under the rear seats. You may also run the wire under the plastic trim that goes along the floor and then up through the sides of the rear seats Once you get the power wire to the trunk, or wherever you are wiring the amplifier, move onto the signal wires.
Remove the stereo from the center console using the instructions above. Connect the Amplifier Turn On wire you got in your wiring kit to the corresponding wire off the back of the stereo. This is usually blue.
Next connect the RCA cables if you are using them to take the signal to the rear of the car.
Route the RCA + Amp Turn On wire either through the plastic trim along the outside of the car or under the carpets like before, but DO NOT LET THEM TOUCH RUN ON THE SAME SIDE AS THE POWER WIRE TO AVOID INTERFERANCE.
Pull all the wires through to the trunk.
To ground, find a metal spot close the the Amplifier and scrape away all the paint in a small 1" diameter circle(I like to remove the paint with a wire brush attachment on my drill then sand away after that to ensure removal of all the paint). Drill a hole in this circle and then take the ground wire and a metal (preferably grounding grade(green usually))screw, and screw the ground wire into place. The more bare metal and less paint on the metal panel, the more solid the ground connection.
Mount your amplifier.
Connect the amplifier turn on, power wire, ground wire, then RCA wires (in that order if you would like to, doesnt matter too much)
Connect your speaker wire you your amplifier, then connect it to your subs/speakers.
Check all connections, put everything in its place, reassemble the console. Make sure nothing is pinched.
Put the fuse in the fuse holder under the hood.
Enjoy your new subs/speakers. Just go easy on them for a few weeks, no loud music, or they will not break in properly.
(I cut and pasted some of that. I skimmed it pretty well, but I'm sure there are still a few things I disagree with in some of it, it's mostly basic information, and generally helpful though.)
there are 3 basic ways to kill a speaker: mechanical overload, thermal overload, thermal fatigue. power will not blow a speaker, whether too much or too little. you may feed a subwoofer any amount of power you wish. As a general rule, if you can't hear distortion, you will not blow the speaker.
unfortunately, even this is a misleading and fallacious statement. the bandpass box user will be delighted and crank the volume, hearing no distortion and thinking himself set. No relationship is made between the three methods of speaker destruction and power handling, such a discussion would most likely be too long and drawn out for a general bulleted tip list.
I dunno, I guess if I had to compress it down to a bullet, I would say something like: "power doesnt kill speakers, whether too much or too little. overuse of the gain know plus overuse of the volume **** kills speakers"
and again, its still not enough, it doesnt call for how much gain or volume! its a tricky one to bullet, I dont think I can come up with anything thatll be good.
Now, here's a few links that could also help some of the audio newbs...
First, here's my sound deadening FAq thread:
https://www.scionlife.com/forums/vie...ight=deadening
eCoustics- www.ecoustics.com Lots of information contained there, reviews, basic info, detailed info, forum, etc...
Basic Car Audio Electronics - http://www.bcae1.com/ - This site has it all. Everything you could ever ask is discussed here, but yet its extremely easy to understand here.(There's a bunch of links down the right side, navigate there, not on teh large left portion of the screen. It's a tan colored area)
Eddie Runner's site: http://www.installer.com/tech/index.html - Has some interesting articles about interesting stuff
Car Audio Usenet FAQ - http://www.mobileaudio.com/rac-faq/rac-faq_toc.html - Lots of basic information
Crossover Design Calculators - http://ccs.exl.info/calc_cr.html - For those that want to make their own passive crossovers
The Polyfill Article - http://www.win.net/audtatious/audio/fiber.html - Learn exactly how much box stuffing to use for your desired enclosure and what box stuffing really does for enclosures
Car Audio Forum - www.caraudioforum.com - Forum and chat room, chat room is owned and run by a friend of mine. Feel free to stop by and watch the freakshow
Elite Car Audio - www.elitecaraudio.com - Tightarsed high end audio junkies. They get annoying and stuck up on the forum, but they know their stuff quite well
Sound Illusions - www.soundillusions.net - Another good site
Port Tuning Calculator - http://www.2k4civic.com/portcalculator.html - A simple port tuning calculator that gives you a tuning frequency for a square or round ported box
Hopefully some of or all of that information helped you and maybe some other people on here understand some things they were having some trouble with.
Yeah, I know it's really long, but I still feel like it's worth the read, especially if you're just getting into car audio, or even if you've been into it for years. I'm sure there are people here that aren't going to learn anything, or aren't going to agree with everything. That's fine too, if you disagree, post so, and give reasoning. Sometimes the best way to a solution is to get opposing views to get the best possible answer. In my opinion, the information is accurate (to the best of my knowledge) and correct. Sure, I haven't skimmed it in a few days, so there's probably something I don't agree with in there, but it's probably minor information. I'll reskim it again in the near future adn edit it as I see fit. If you have something to add, or a question to ask me, feel free to post or PM me.
07-20-2005, 04:22 PM
#12
Senior Member
SL Member
Join Date: Jan 2005
Location: Wheaton, IL
Posts: 2,030
Originally Posted by jaydub
Originally Posted by AldoRx
Alot of it is a matter of opinion.
One point I seriously disagree with is that BASS IS OMNIDIRECTIONAL.
I've worked in studio and home theater acoustics for years. I build and design
professional sound absorption and diffusion. I have a good idea what I'm talking about.
Read VERY carefully. BASS IS OMNIDIRECTIONAL! The reason you can pinpoint
where your subs are, is because the air/sound from the sub is MOVING/RATTLING
objects and its THOSE objects (if not the air itself) that are giving you ear audio
cues as to where the bass is. NOT THE BASS, BUT WHAT THE BASS IS MOVING!
I think the point of mid drivers and frequency response is very subjective.
Maybe you didn't make your point clear enough for me to understand, but it came
off as "use JL VR or your setup will sound like crap". Could you please try and
clarify that point to me?
As for the info on caps, I'm not as experienced with electrical as I am Audio/Video,
but I've hand built several vacuum tube guitar amps and understand Ohms law
pretty well. I honestly can't contest anything written about caps not being able to
provide power when in need...or at least not enough to make much of a difference.
The same goes for the guitar amps I build; The caps are used to filter noise or filter
frequencies and not much else. But the theories are the same.
From what I gather, it still boils down to what those who truly know audio have always
said, get the BEST alternator/regular you can afford, and a "Fast" battery.
Correct me if I'm wrong?
P.S. Yes I did read every word here...I do wish I could see the charts/graphs mentioned
in the lessons.
07-20-2005, 05:08 PM
#13
Senior Member
SL Member
Thread Starter
Join Date: Apr 2005
Location: A-Town
Posts: 176
Bass doesn't really become omnidirectional until you go below the human hearing capacity. What we can hear is not omnidirectional.
I'm not an advocate of caps, I never have been. The information was to show that caps can not increase output voltage. Contrary to circulated myths, caps can not keep a vehicle's charging system at a constant 14.4 volts. Never have been able to, never will be able to stabilize voltage. I am a big advocate of the big 3, battery, then alternator (alternator being last). Those have a guranteed effect on dimming problems. True, a cap [b[can[/b] possibly help with dimming, but they don't always work.
The JL VR's were just an example. I used them to show that no, you don't always get what you pay for. I hate when people say that because it's not true anymore. That's merely all. I never stated that they are what to get and nothing can compare. I was simply using them as an example.
I'm not an advocate of caps, I never have been. The information was to show that caps can not increase output voltage. Contrary to circulated myths, caps can not keep a vehicle's charging system at a constant 14.4 volts. Never have been able to, never will be able to stabilize voltage. I am a big advocate of the big 3, battery, then alternator (alternator being last). Those have a guranteed effect on dimming problems. True, a cap [b[can[/b] possibly help with dimming, but they don't always work.
The JL VR's were just an example. I used them to show that no, you don't always get what you pay for. I hate when people say that because it's not true anymore. That's merely all. I never stated that they are what to get and nothing can compare. I was simply using them as an example.
07-20-2005, 05:49 PM
#14
Senior Member
SL Member
Join Date: Jan 2005
Location: Wheaton, IL
Posts: 2,030
OK, here is the theory behind Bass being Omni-Directional.
The way your brain figures direction and distance is through
Stereo. Both with your eyes, and ears. I'm sure you've heard
that someone who only has one eye, has no depth perception.
This is because your brain, being the amazing computer that it is computes the
difference in the image one eye sees compared to the other and calculates depth.
Same thing with your ears.
If you close your eyes and someone to your right claps, the wave passes your right
ear first, then your left ear. Your brain calculates the time it takes to pass and
says "hey, that's to the right and a little bit forward". Makes sense right?
Well here is were true Sub-woofer comes in. The distance between the ears
on a typical human head is about 6.5" (funny how 6.5" drivers are said to produce
the most natural reproduction, huh?). Now as the frequency of the sound, whatever it
is, gets lower, the vibrations get WIDER. If you were to see a high pitched squeal
on a scope, it would be a really tight wiggle of a wave. As you go lower, those waves
get larger and larger. Once those waves get larger then the 6.5" (average) distance
between your ears, your brain can no longer sense which side of your head the wave
originated from because the wave is now bigger then your head!!
This wave that gets bigger then your head is right around 80Hz. Right about where
our subs should start working and our mid drivers should be rolling off.
EVERYTHING below 80Hz is BELOW the range that our ears can sense direction.
As you get closer to 20Hz "limit" of the typical human ear, the waves are 40 feet long!!
So unless your head is 40 feet wide, your brain CAN NOT hear the direction of BASS
at those SUB frequencies!
If you can point out where the sub is in any setup, it's because of audio cues or
higher frequency (harmonics) of the note resonating from things around the sub,
the wooshing of air through a port, or even resonation of the sub-box itself if it's not
built very well (long unbraced panels)...or a bad (high) crossover point. If your subs
are extending over 80Hz then yeah, you'll hear where they are.
This is all very simple science and is known by every audio engineer since the early
days of sound reproduction. This is nothing new, nor some internet-hype. Do the
research yourself if you'd like, but I've summed it up pretty well here. You could
simply Google "bass is omnidirectional" and 80Hz and you'll see this is common
knowledge.
The way your brain figures direction and distance is through
Stereo. Both with your eyes, and ears. I'm sure you've heard
that someone who only has one eye, has no depth perception.
This is because your brain, being the amazing computer that it is computes the
difference in the image one eye sees compared to the other and calculates depth.
Same thing with your ears.
If you close your eyes and someone to your right claps, the wave passes your right
ear first, then your left ear. Your brain calculates the time it takes to pass and
says "hey, that's to the right and a little bit forward". Makes sense right?
Well here is were true Sub-woofer comes in. The distance between the ears
on a typical human head is about 6.5" (funny how 6.5" drivers are said to produce
the most natural reproduction, huh?). Now as the frequency of the sound, whatever it
is, gets lower, the vibrations get WIDER. If you were to see a high pitched squeal
on a scope, it would be a really tight wiggle of a wave. As you go lower, those waves
get larger and larger. Once those waves get larger then the 6.5" (average) distance
between your ears, your brain can no longer sense which side of your head the wave
originated from because the wave is now bigger then your head!!
This wave that gets bigger then your head is right around 80Hz. Right about where
our subs should start working and our mid drivers should be rolling off.
EVERYTHING below 80Hz is BELOW the range that our ears can sense direction.
As you get closer to 20Hz "limit" of the typical human ear, the waves are 40 feet long!!
So unless your head is 40 feet wide, your brain CAN NOT hear the direction of BASS
at those SUB frequencies!
If you can point out where the sub is in any setup, it's because of audio cues or
higher frequency (harmonics) of the note resonating from things around the sub,
the wooshing of air through a port, or even resonation of the sub-box itself if it's not
built very well (long unbraced panels)...or a bad (high) crossover point. If your subs
are extending over 80Hz then yeah, you'll hear where they are.
This is all very simple science and is known by every audio engineer since the early
days of sound reproduction. This is nothing new, nor some internet-hype. Do the
research yourself if you'd like, but I've summed it up pretty well here. You could
simply Google "bass is omnidirectional" and 80Hz and you'll see this is common
knowledge.
Thread
Thread Starter
Forum
Replies
Last Post
Beesh
Scion xA/xB 1st-Gen ICE & Interior
3
01-09-2015 06:30 PM
