Well I’ll start by telling you my setup:

(2) 2006 Kicker S12l7, wired to a two ohm final load
Pioneer Deh-7800MP head unit
MMATS D2100.2 amp
Power Acoustic 2 farad cap.

Each sub in enclosed in at least 1 cu.ft. sealed fiberglass/wood box
Each sub is rated @ 750 watts rms
Amp is rated 1550 watts rms @ 2 ohm load
The two 2 ohm voice coils of each sub are wired in series, and then the wires are in parallel to give a final load of 2 ohms
Low pass filter set @ 80 Hz
4 gauge wire to the cap/amp
16 gauge to the subs.


Ok now I’ll tell you the problem I am having:

The subs will sound great up to a certain volume level, and then when I turn the volume up one level, the subs seem to play at a higher frequency (I’d say somewhere above 100 Hz) and because of the higher frequency the subs don’t sound as loud.

I would like to know if anybody has heard of or had this problem and what to do to fix it.

Thanks.

 

your pioneer has crossovers in it. set the interiors to 80hz -12db's and set the sub to the same or 63hz like i did. it shouldn't play very much set at 63hz.

 

i tried that and it is still having problems
i think the sub is bottoming out, idk
what does bottoming out sound like?

 

dude your gain is set wrong then, when you hit that point your finally sending a clipped signal which usually sounds like bass twice the frequency high, redo your gain for the highest your ever going to turn your headunit up to

 

check your LPF on your deck and make sure its about the same freq. on your amps LPF. i usually set mine around 100 (mainly cause thats about where a drum kick usually is). also with that deck, check your slope and try setting the slope more steep so it wont get those frequencies. i could be wrong though.

 

I think it might be the subs, because I can leave the gain on the amp half way up and when I turn the hu volume up I get the higher frequencies, I also get the higher frequencies if I leave the hu on a certain volume then turn the gain up on the amp.
I know the problem is not in the hu because I hooked a home audio receiver to the car amp and at a certain level I got the higher frequencies.
Like diminishedpower said the amp could be clipping, what are some attributes of clipping, and what does it sound like. How could I make it stop clipping with the volume turned up?

 

i told you, your expecting too much out of your system, just turn gain all way down, Then turn headunit to highest you will ever play it. Stick in a solid 50 hz -3 db tone track on loop and then turn up gain on amp untill you hear the sound like its a lot higher frequency then turn down a bit. Thats the loudest your going to get out of the amp, if you want louder, you need to buy a more powerful amp

 

disclaimer: by doing this you will have correctly set your gains, but your sub is not going to be any louder than it was before it made the bad sounds before, just more balanced, If you want more, you need a bigger amp

 

With a bigger amp, he won't get any more SPL in this situation.

No one is considering power compression, people here never do. Just because a sub is rated for 1000 watts or whatever, that doesn't mean it's output will remain linear over it's power range. The ratings imply it can handle the heat, pressure and other variables with a given amount of power, but they don't tell you that there may not be any incentive to give them full rated power.

What's this mean? We know that each time you double the power, the sub's output should increase by 3 dB. In the real world, that's only true up to a point, then you run into "power compression", where twice the power produces something less than the expected 3 dB. For example, a hypothetical 10" 2000w sub might hit 120dB with 100w, 123dB with 200w, only 125dB with 400W, just 126dB with 800w, and remain at 126dB with 1600w.

As for the OP, it does sound like the system is likely clipping, and could be experiencing power compression too (although the latter doesn't contribute to the described issue as much as the former), and setting the gains appropriately would likely resolve it.

 

nodsetse i do know about power compression but for this application it doesn't apply(as in it will gain from more power). Do you have L7's? have you messed with them? i have, and they have room to get louder with more power assuming he doesn't have a whacked box. And as for your comment about power, there is no sub like your exaple unlesstheres an extremely effiecent sub out there i havent heard of, most subs will make decent gains with double the power, may not be the whole 3 db (some more again depending on design and box) but no sub is not going to see a gain from 800 more watts

 

p.s to prove more power will give more out put, OP said the sub was getting louder up till it clipped, aka theres still more room, if power compression was in play, as you turned up volume you would hear gain in loudness Example:

Your head unit is set for max output for the sub at volume level 40, Your sub gets ouder as you turn up volume untill you hit 30, then from 30-40 the sub doesn't clip but doesn't get louder, thats power compression.

Whereas if the sub kept gaining loudness at you went all way to 40, then it could take mroe power and gain output.

 

^ What I stated was general info, intended to provide people with an understanding of another factor they should consider, but most aren't even aware of. The whole thing wasn't directed at you specifically, so don't take it personally. However, my statements about power compression are factual, so I hope others gain something from it, even if you choose to discount what I attempted to convey.

Not sure why you'd pick on the example I gave, unless you don't know what "hypothetical" implies, and/or can't correlate such to a real-world scenario. Pick a sub, practically any sub, and you'll find it have increasing amounts of power compression at every output level, as the output doesn't remain linear with more input wattage. It's the same with the 750W L7s in question here, so you can use them as a substitite for my imaginary example if you'd like. You'll never know how an L7 is in this regard without testing it for such, so I wish you wouldn't be so pretentious just because you've "messed with them", as you put it.

I understand this aspect of audio very well, along with how to set the gain structure of a system appropriately, but your "example" of power compression is misleading. Your description could be attributable to aspects other than power compression, but I've run out of time to elaborate further today.

 

if your getting higher freq's through the sub your crossovers aren't set right, did you try the sub at 63 with the -12 slope, and the interiors at 80 with a -12 slope. set the actual crossover an the amp as high as it will go since your deck will be in control of the crossovers. thats what i use and it sounds good and blends with the interiors very well.

 

its not crossovers that would affect everything, this happens only when he turns volume past certian point, or messes with gain, its a gain issue

 

so the only way to stop the clipping is to get a better amp? what amp do you guys reccomend, and also will a high output alternator help any,and if so what kind of effect will i hear? even though the amp is rated at 1550 watts rms, it does not seem to be putting out that wattage, is it a cheap amp or do you think that i have the subs set up wrong in too small of a box. should i just follow kicker's ported box recomendations or does any body know of a better box design.
and the amp has its own lpf that is set at 77 Hz and it has a slope of -24dB

 

i dont have personal experience with mmats brand but, what voltage is your amp seeing? (im guessing your cap tells you) second a bigger alt always help specially if its a nice one that is regulated at 14.4v. If you do get a new alt def get rid of cap, its just a bandaid.

Second you will have voltage drops with normal alt so your no way sending the rms of the sub(200 wats wont make a diff, but L7's can take 1k daily or more, so if you got a bigger amp a 2k amp would due it well)

Third, Bigger amp will not stop the clipping, i was saying once you hit the clipping you reached the max output of your amp.

 

No, it's not a "cheap" amp, MMats has been around a long time, they've got a good reputation and make great class D amps for subs. It really does sound like your issue could be resolved by the appropriate system gain settings. If you verify everything is set optimally and still have the issue, have a good shop test the amp to ensure it's not defective, as things can go wrong with any amp brand/model at any time.

The 4th order slope is great, and 77Hz is fine, but you could also lower it to the minimum 70Hz setting and that might improve the SQ slightly. If you're concerned about underlap between the sub and sats, don't worry, as most people have the gains set such that the sub's output is so much higher (in comparison to the other speakers), that it makes up more than the difference between the crossover settings.


While you're not familiar with MMats, do you have experience with amps using regulated power supplies? They don't operate the same way unregulated designs do, and parts of your answer apply more to the latter than to the amp the OP is using. His amp's output doesn't drop when the input voltage is decreased (up to a point) the way more typical unregulated amps do, and the way they draw power (current, duration and interval) places somewhat different demands on the charging system.

If a pair of the 750w (each) rated L7s can handle 2000w as you implied, and IF their output also remained linear at such power levels (that's a big IF), then going from 1500w with his current amp to a new 2000w amp would only result in 1 dB more SPL. To each his own, but even considering the cost alone, there doesn't appear to be much value in such an "upgrade".

 

I was not aware that it was a regulated power supply, hence me not knowing about those amps, and in which me thinking it was unregulated i figured he was pushing way less and with a nice 2k he would have more of an increase.

But as you said to each there own, if the op doesnt want to spend a lot of money but wants more ouput, i personally think the L7's shine in ported but again you "loose" sq but sq is objective and highly dependant on the box design.

 

The cap says 14 volts with the car running, but it drops a little on a big bass section and then goes back up to 14 on a little bass streak.
Second, i live about an hour away from the mmats factory in Florida so i might take it to them to see if it working properly.
The setup I have now does not seem to be anywhere near 1500 watts rms, this may be because the small sealed enclosures, and also will I hear a big difference if I make some ported boxes? And should i just stick to kickers ported box recommendations or does any body have any experience with these sub in ported boxes?

 

Well if MMATS is so close and if there nice guys they should be able to test it and maybe even check to see if you have things set up, theres always the chance you do have the subs being hooked up to wrong ohm load on accident.

And ported theoretically will give you around a 3 db increase, but its all box dependent, and just search around for what people have done with there ported, but i will speak from experience, unless your fiberglassing and getting rid of your spare tire i dont think your going to find room for two 12's ported in optimal spacing.