xbdition

Has anyone modified the capacitor crossover on the stock tweeter? Stock they have a 3.9 microfarad cap that crosses over at 10khz. That means the woofer takes up all the midrange responsibilities up to 10khz and beyond, and does a horrible job at doing it.

So, for fun, before I jump into and find time for a full stereo, I replaced the cap with a 10 microfarad cap which should cross the tweeter over at just shy of 4khz. Midrange is better and the soundstage is higher. Maybe a little too high, but worth it compared to the crappy mids the stock woofers put out.

It in no way sounds as good as a decent set of amplified components, but at about $3.00 for two caps, it was a cheap and quick improvement.

xseveredveganx

Nice! Not a bad idea!

xbdition

Thanks man. I'm tempted to throw an inductor coil on the woofer, but if I had the time to do that, I'd be better off just upgrading everything. For now, the little cap mod will have to do.

TrevorS

iTrader: (1)

Only thing is you're directing a lot more power into the tweeter than it may be comfortable with (and you're also beaming the midrange (EDIT: foot in mouth disease -- this condition results in driver decoupling, the reverse situation results in beaming, sorry about that )). I would strongly recommend upgrading the door speakers rather than lowering the crossover frequency. However, if you upgrade the door speakers, you'll need to damp the door panels as well. Still, I recommend biting the bullet rather than ruining your tweeters -- I find they work very well with the OE crossover and aftermarket door co-axials (midrange and bass) plus receivers.

xbdition

Weeeellll, if you want to get technical, crossovers don't split power, they split frequencies. The tweeters are getting as much power as they were before, just at lower frequencies. They handle the 4khz up range just fine and they're only seeing about 17 watts RMS from the headunit.

Yes, there may be impedance rise as the frequencies go up, and less power will be seen at higher frequencies, but...meh, if they can't handle 17 watts down to 4khz, I can't wait for them to blow so I can replace them with a proper setup. I'm not worried about replacing them as I've got a closet worth of gear waiting for some time to be installed.

I'm not sure what you mean by "beaming" the midranges and if by "ruining" you mean changing the capacitors, but like I said, all this stuff is just until I get time to install. Thanks for your input.

TrevorS

iTrader: (1)

It just so happens I very well know what I'm talking about (have been heavily into audio for many years) and what I said is entirely accurate. However, it's your choice and I'm only offering advice -- do what you will, but I hope others will be careful about copying your example.

PS. There will be no reduction of high frequency power, but there will be addition of midrange power (it's the additional power that puts the tweeters at risk). Also, beaming occurs as the frequency gets lower compared to the diameter of the driver (EDIT: foot in mouth disease -- this condition results in driver decoupling, the reverse situation results in beaming, sorry about that ).

xbdition

Oh, you're one of those huh? Okay chief

TrevorS

iTrader: (1)

Oops, sorry -- I said beaming, but the problem is actually driver uncoupling with reducing frequency. My apologies ! But that's secondary, it's the additional coil heating that's the real concern, especially if you tend to crank the volume at all.

xbdition

yeeahhh...like I said, okay chief.

If you or anyone else thinks they will blow their speakers with 17 watts RMS, then caveat emptor don't do what I did. Happy? I'm not selling drugs here.

BTW, distortion kills speakers, power by itself doesn't, and I don't buy that you know for sure there will be no impedance rise. I only mentioned impedance rise to give some credence to what you were saying.

I've given my re-capped tweeters as much as my headunit could handle, and they don't distort, but hey, you need not do as I say or as I do.

TrevorS

iTrader: (1)

Just pointing out, these aren't full range speakers, they're tweeters and designed for a limited bandwidth. Absolutely, if an amplifier is driven to the point of clipping, resulting high frequency energy will likely result in damaging the tweeter. However, that is just one way to deliver excess energy to a tweeter. A crossover that is set too low can accomplish the very same thing by requiring the tweeter to handle more energy than intended (can result in excessive heating that can damage the voice coil). Just be aware !

xbdition

I don't think you have a whole lot of real world experience despite your being "heavily into audio for many years". Now you're spouting off a bunch of irrelevant information, alot of it bordering on distortion and disinformation. I think the problem is that you assume I know a whole lot less than you, when you don't actually know that much.

How likely do you think it is that anyone will be able to cause clipping with high frequency signals? What you say makes perfect theoretical sense, but does anyone listen to a sinusoidal wave through tweeters? Does music, podcasts, news, or what have you ever approach this theoretical possibility in the tweeter range?

Theres nothing special with the stock tweeter. It is a polymer tweeter that looks like it is 3/4". Tweeters typically have a useable range from around 2500hz and up. Also, most tweeters have a natural rolloff well before you approach the kinds of frequencies where clipping is a real concern. You are right, these are tweeters, and not full ranges. It's quite obvious. You point this out because you think it isn't obvious, or because you think I wouldn't notice?

Do you think these tweeters were specially made for Scion XB's so that they can't handle 17 watts? Let me point out to you that we are talking about headunit power which is optimistically rated at 17 watts RMS. It also likely sees alot less power than 17 watts at 4khz and up.

All of your techno jargon has contributed nothing so far. You've only accomplished getting your ego bruised because you thought I was questioning your technical knowledge, and now you just keep piling it on because you want to get the last word in.

This started as a good natured thread, just wanting to share my experience, but you've drawn me in to this type of back and forth because, as I said before, you're one of "those".

TrevorS

iTrader: (1)

Your thread is fine, but you've made it clear you have very limited understanding of audio speakers, despite your bold words. I've no interest in argument and it's not my problem. You and anybody else are free to abuse their drivers in any way desired. You say you plan on upgrading the drivers anyway, and no doubt that'll be a good move! I just happen to like the OE tweeters and would hate to damage them unnecessarily. To each their own, happy listening !

KaneoheKoa

I just have to put my 2 cents in (adjusted for inflation, natch!).

The design of the stock speakers are a variation of a simple coaxial design, except they moved the tweeter higher up. The woofer runs full range and the tweeter "sweetens" the sound. The woofer has a natural drop in tonal range (more pronounced as the tone goes up). Many 6" woofers start to roll off at about 4k-6khz or so, which is still pretty high up on the music scale. Ideally, the tweeter would start playing close to those frequencies. Good tweeters regularly play very well in that range, but they cost more. So, we get a more cost effective tweeter (ie, cheap) that plays just enough to sound okay in the showroom (where you're excited about everything else in the car).

Good two way systems have crossovers for the tweeter and woofer. The simplest (called Butterworth) use only 2 parts: a coil (or inductor) that blocks highs from going to the woofer (called low pass, as it only passes the lows), and a capacitor that blocks the lows from going to the tweeter (high pass). Now each speaker plays in its comfort range (at a 6dB per octave rolloff curve). Other designs use both a coil and cap for the woofer and coil/cap for the tweeter (now 12dB per octave), yielding an even clearer sound, at a higher price. And it goes on with more parts, adding in resistors, more coils, more caps until you can't afford it if you have to ask the price. But I digress. Typical separate systems use the 12dB crossover design; good sound, affordable.

As to how much power the tweeter in handling, it is correct that the more bandwidth it's given, the more power it has to handle as heat. So, you could overdrive your tweeter with 17 watts. The flip side is that you really don't need much power to make tweeters sound loud, hence you're not pushing a lot of juice into the tweeter, and not heating it up. You can blow them out by overdriving them, but you'll hear your woofers distorting like mad before that happens and then turn down the volume (hopefully).

A common misconception is that distortion destroys speakers. Actually, it's amplifier pushed into clipping that does the deed. The cause of this is trying to make an amp play harder than it's design. An unclipped sound wave goes up and then comes down immediately (think of a pyramid). Clipping flattens out the "peak" into a flat (for this illustration) long top, then back down. Now, think of a light bulb being turned on and off. 1 second on, 1 second off and so on. It'll get warm, but then have a chance to cool off. In clipping, the bulb may be on 1-3/4 seconds, but off for only 1/4 seconds. Bulb gets hot, remains hot, but doesn't have much cool down time. Hence the bulb gets too hot to handle. In the tweeter, this heat either burns out the finer than hair thin voice coil wires or melts the coil insulation and causes a short. This usually happens when a low power amp is pushed hard and it sometimes happens fast. Rule thumb: bigger amps are harder to clip and are safer for speakers (when played within reason).

Modifying the stock sound system is actually fun, and you do learn from it. xbdition, if you really want to get into the thick of diy speakers, check out Parts Express and The Loudspeaker Design Cookbook, the veritable bible for speaker builders. Good luck and have fun.

Trivia: in a two way crossover using a Butterworth design, the tweeter is normally wired in reverse polarity, as the capacitor initially swaps the polarity. Of all the affordable crossovers, the Butterworth design gives the most phase coherent sound. The cost is that the speakers play a wider range, so the sound is a little muddier.

xbdition

Ok Trevor, next time I want an unsolicited and uninformed recommendation, I'll let you know.

In the meantime, and back on topic despite all the salt in here, my tweets are rockin! It may buy me a few more more months before I get over my laziness and go active in this box.

Cue: {Last word} That's your cue chief.

xbdition

Kaneohe, I get all that stuff, and I dabble in DIY a bit. I've ordered quite a bit of components from PE and Madisound. I have to disagree about distortion not killing speakers though. You can kill a speaker with low watts and a distorted signal played too loudly, exceeding either the thermal or mechanical limits of the speaker.

Not to belabor the point, but although clipping can kill tweeters, if you have a clean signal and are listening to what practically 100% of people use their speakers for, music or other audio programming, you don't have huge signals in the 4khz and up range playing for several seconds wherein damage would occur. It can happen, but its not likely if your tweeters get a clean signal and are crossed over.

Whatever portion of the available 17 watts the tweeters are seeing, depending on frequency, is a clean signal, and I don't believe that the tweeters can't handle the thermal load of less than 17 watts.

Also, they are far from reaching their mechanical limits, something that would be audible.

So, in sum, yes the points you bring up, and even the ones Trevor has "can" happen, just not very likely. I could also jab a pencil through the tweeter, and I'm sure it would sound like crap afterwards and be considered speaker abuse, but it's probably not going to happen.

Maybe if you consider that sounds in around the 4-5khz range are "frictive" sounds such as "ffff" and "vvvv", it will make it clearer that the risk of clipping in that range is low. Above and beyond that, its all very transient sounds, unless you roll around listening to pink noise.

Zeppsin

Hey folks, I been looking at all types of options for my system. My scion factory pioneer T1808 is okay, but I blew two speakers. I'm going with new ones. four-6.5 new Polkaudio speakers & two polkaudio tweeter. once I see how they sound in the car, O might get one of the 4-channel amps (GM series pioneer amps) Looking for ideas. Also I need a ipod chord upgrade to the gs3 so it will charge!! If these smart phones where so smart... they'd stay charged longer! ha-ha

xbdition

Seems like you're all set with your gear, except for a subwoofer. What kind of ideas are you looking for?

If it were me, I'd skip replacing the rear speakers and put more money into a better set of front components and a better 2 channel amp, or use the money saved on the rear speakers towards a subwoofer and amp. I would also definitely change the headunit. With my stock headunit and stock speakers, there is a hump in the frequency range around the 2khz range that is very fatiguing on the ears. I installed an old pioneer nav unit that has a built in adjustable EQ function, and decreased the 2khz range about 3-4 db and it sounds much better and pleasing to my ears. I've also never installed a stereo wherein no EQ'ing was required, so just installing speakers and an amp may not make you happy.

You'd probably get a lot more feedback with your own thread, fyi, though I'm not claiming this one as exclusive.

Zeppsin

you make a good point! I i listen to lots of music.... Aerosmith, tool, perfect circle, Ozzy, disturbed... the all blues! i play bass and feel the music. I keep the volume between 30-40 on mt t1808 headunit ha-ha I just don't want a boom boom sound i want too hear the differences in instruments.