Is your woofer a "stock" woofer, or does it have a bunch of custom options? And yeah, the DD Z's I've always seen like bigger boxes. Like the 10 IIRC, so don't quote me exactly on this, wants 1.75-2 cubes ported. I wouldn't be surprised if the 12 wants something like 3 cubes, 3.5 cubes. The DD Z, IMO, is the most serious subwoofer you can get your hands on. Literally the most powerful subwoofer of all time, that I know of. So take your time figuring it out.