never used a prefab box, never will
also that e12dtv box isnt close to 4 cubes, its 3.9 gross before any port or woofer displacment, in all reality that box is 1.25 cubes per chamber.
I wish i could say i never used prefab lol. all prefab is shit, aside from sealed if it's proper volume. even then it's cheaper to make your own.