[Zero the Hero]

Meaning what? Four SW-12Bs in a sealed box, 6-8 cubic feet total.
Why four sub drivers? Not for max SPL; but for bass extension mainly (which is why the "sealed" part). This would be for HT use, with music secondary. I'm looking for decent output into the low teens or even single digits. Power with a bridged Behringer A500 (500 watts/8 ohms), and I should be left with enough headroom to eq a little extra on the low end and eq enough out of the upper bass to flatten it out. Yes, for the same money I could buy a nice Mal X 18" driver (curiously with 500 watts and 8 cf the curves are IDENTICAL) but the 12's have a little more surface area and more flexibility with box shape. (Plus it would look pretty cool...)
Negatives to this plan?
Danny, are there threads on those drivers to add mass if I wanted to try that road?

[Danny Richie]

Unless you add a transform circuit or add a lot of boost to the bottom end then you are not going to get extension into the low teens in a sealed box. Upper teens might be a bit more realistic. If the Behringer will do all of this for you then you may be home free.

I don't think you'll need to go for adding mass to the drivers. This will just add more stored energy and inertia to the mix and that would not be a good thing.

[Zero the Hero]

Thanks Danny -
my thought process was that the low Q of the large box (.6ish) would give SOME extension down low, admittedly down quite a few db. But, with room gain, a little eq, and trimming 8-10 db from the top 2 octaves (20-80hz) it would flatten it out nicely.
If that doesn't work I guess I could throw out the box and build 2 large ported boxes and forget about the really low stuff...

perhaps if we built a large wooden badger....(obscure reference just popped in my head)