Subs not making bass like I expected.

I have made boxes many times and always had good results until now.  I have always gone with ported boxes.  This is the first sealed box and the first time I have had very expensive subs and amp.

In the past I have always gone with Pioneer amps and subs.  To say the least, the bass would make dirt jump out of the carpets.  I just finished my install in my 2000 Integra.  I have the Pioneer Premier DEH-940MP head unit.  The front and rear stage are running off one GM-X1034 amp.  Front stage are Focal 165 K Polykevlar 6.5" and Boston Rally 6.5" bringing up the rear.  The 2 12" are running off another amp.  They are Pioneer Premier TS-W12PRS subs.  They can handle 1200W max.  The sub amp is the PPI PCX-2400.  It puts out: 400W x 2ch @4ohm,    800W x 2ch @2ohm,    1600W x 1ch @2ohm

The enclosure is sealed at an approximate interior volume of probably less than the recommended 1 cu. ft. for each sub.  Honestly, how critical is exact interior volume?  If I'm off by .25 cu ft., will deep bass be impossible?

What happened was my friend built the box while I wired the car.  There was an error in calculations with the enclosure panel cuts and we had to fix the incorrect cut by shortening a couple of pieces.  The result is obviously a smaller volume of air inside.  I did use fiberglass pink to insulate each wall and the subs are firing outward from the box.  The box has a rear wall angled to match the angle of the rear seats and the subs fire towards the rear of the car.  The subs are 4ohm DVC and the wiring is Series/Parallel to achieve 4ohms into one channel.  The box does not appear to have any air leaks.

I do not find the bass to be sub like.  The box hits incredibly hard bass but no sub-bass.  I was thinking of inverting the subs and the wiring to try to increase the interior volume.  Does this make sense?  What can I try to figure out what has been done wrong or what have I missed?  I have played with the amps crossover and gain.  I have also set eh radios crossover and sub gain.  I can only see the problem being the enclosure volume.

Any suggestions?

If your interior volume is off by 0.25 CUFT, making it closer to 0.75 than to 1.0, then yes this will definately cause loss of low bass and you will probably not be able to hit below about 40Hz with those woofers.  There are a couple things you can try, but there are no guarantees short of rebuilding.

First, take out that damn pink fiberglass insulation.  That stuff is intended for houses, and for audio it is crap and can actually damage your woofers. Loosly fill the interior with about 1 pound of polyfill, either genuine audio grade (like Acoustastuff from Parts Express) or dacron pillow batting from a fabric store.  This will increase the enclosure size by approximately 0.1 cuft. 

Second, you could also try inverting the woofers, as this will increase the enclosure size by the volume now taken up by the speakers plus the volume inside the cone area.  These two things in combination should get you back to about 1.0 cuft.  This is still too small for those woofers, however, as Pioneer recomends 1.5 cuft sealed for their 12" Premier series component subs.  Remember if you do invert the woofers to reverse the polarity, either by reversing the wiring or by switching the amp 180 degress out of phase.

Your best bet in any case would be to rebuild the enclosures, though.  Go for 1.5 cuft.  And don't use house insulation!

In the past, the Pioneer subs I have always used called for 1.5 cu. ft. of volume per 12".  However these subs called for 1.0 cu ft. of volume.  That's the only reason I went that way.  Your thinking 1.5 might be better.  I have no problems rebuilding the box.

As for the Acoustastuff, you mentioned loosly filled.  Do I staple it to the walls or simply place it in the box?  I will probably invert simply because it looks cool.

I second DYohn's info.  Listen to him!

Yep!  And yes, I recomend building 1.5 cuft if you intend to rebuild.  Make it 1.5 ACTUAL cuft and do not take the woofer displacement into account.  Then after installation you will end up around 1.3 to 1.35 and it should sound good.  This is per woofer, of course.

On the other hand, for inverted subs, I think I'll go 1.4 with Polyfil.

You da man Dy.

Are you sure the speaker wires are hooked the same way? + to + and - to - ?

just an idea,i know ive made the mistake b4 and the end result is no base.

Huh?