1. Stereo Integrity's BM mkIII...

If you want to see where shallow subwoofers are heading in the future, just look at where the SI BM mkIII is today. At only 3.5" of mounting depth, 50 % more linear excursion than the TW5*, a miniscule 0.5 ft^3 enclosure requirement, and 450 watts of power handling, the BM mkIII has a big subwoofer attitude in a shallow package.