Box Too Big

Alright.  Turn off the subsonic filter.  You don't need one - ESPECIALLY one that high - with a sealed box. 

And yes, you probably do have a severe hole between the midbass and bass.  (80 to 125).  AND it is probably much larger than that.  I bet your 55hz is MUCH hotter than your midbass, even without the 125hz filter. 

Try running the 10" drivers with the low pass xo at 100hz.  Bump the high pass on the components down to 100hz if you can.

What is the slope of the low pass cross on the amplifier?

My guess is that you've highlighted the problem with 4 10" drivers - you have an unbalanced system. 

Wow ... yes ... I bet I've identified the problem.  You have a severe gap between the bass and midbass regions.  Remember, at the crossover point you are already 3db down.  By 160hz you are 24db down.  Since the subs are probably much hotter than the midbass you probably have major attenuation from 70 to 200hz. 

Also - just to cover all the bases - make sure none of the woofers are out of phase - this could also cause some problems like this.

Alright.  Check this out:   https://www.bcae1.com/xovrslop.htm

See how the slope gets much steeper at 24db?  Your friend's system looks like the crossover point there.  Only the points don't match up - one is at 80hz and the other is at 125hz.  And his situation is even worse - because his subwoofers are probably "hot" (more efficient) relative to the midbass drivers under 200hz.

Just adjust the crossover..

1)  Turn OFF the subsonic filter
2)  Turn the low pass crossover to the subwoofers HIGHER - to 100hz or so.
3)  Turn the high pass crossover to the midbass LOWER - to 100hz or so. 

The idea is to match the crossover points - like the graph in my previous post.

Let me know if that helps at all. 

And like I said - recheck your wiring.  If one subwoofer moves the wrong direction it could cause cancellation problems.

Ok.... a crossover cuts frequencies so the speaker doesn't play them.  It just doesn't stop playing them ---- it reduces at a slope. 

1 Octave is a doubling in frequency....
20 to 40hz .... 40 to 80hz .... 80 to 160 ... etc.

A decibel is the unit used to describe SPL. 
1 db is a very small audible change. 
10db is a doubling of volume to our ears.

The crossover slope describes the decrease in SPL (db) over one octave. 

So, for 6db / octave slope the sound is 6db quieter from say 40-80hz. 
Similarly, from for a 24db slope the sound is 24 db quieter (much more than twice as quiet to our ears) over one octave say from 40-80hz or 80 to 160 hz as the case may be with your friend's setup.

Does this work for you?

I agree with yall solutions but i got one thought. from my previous experiences with multi driver/single chamber boxes that are sealed is that , well its just not good,.Speakers come with a certain size enclosure needed to give the correct air pressure internally in which the speaker can compress. when you got four subs pressing against each other it causes it to not preform up to par. if you feel the box is still big though , or in the future , then try using polyfill ( like for pillows) it causes the resistance inside to increase making to act like a smaller enclosure.

If im just blowing smoke someone tell me please..

djoxilary wrote:

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if you feel the box is still big though , or in the future , then try using polyfill ( like for pillows) it causes the resistance inside to increase making to act like a smaller enclosure.

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Polyfill does "cause resistance" inside an enclosure, but that makes it behave like it was LARGER, not smaller.