Needing a 4th order design

[Ferguson621]

Oh nice, I didn't picture that design, so what happens to the space above the subs? 

 

And if I rebuilt the box would it be a noticable difference in output?

 

I changed the port earlier and it definitely sounds alot better than before

[Joe X]

Note that the subs did not change their original location, I changed the sketch in my previous post to something hopefully easier to understand.

 

[Ferguson621]

Disregard that lol. It was a different sketch when I looked at it the first time.

 

So would that design have better output? 

I'm trying to reach 150.....and I've seen numerous builds with one 18, two 15's, two 12's

 

But I can't seem to get there 

[Joe X]

It's merely a patch up made mainly to avoid potential over excursion due to an oversized rear chamber. It's not different enough from your original design to make for big gains of any kind just by itself. Besides your box would need some serious bracing and sealing probably just to perform on par to what it is.

 

If you are a numbers chaser you will need a more serious design and a much stiffer box, also you need to review the rest of your system, electrical, wiring, gains, etc.