I have got 2 diamond audio tdx's and decided to build my own sealed subwoofer box. The tech sheet says that for 800 watts you should use a 3 cubic foot box, i am only using about 300 or so, i bought the wood and everything allready, will 3.5 per sub after displacment give me good results.(I know i am underpowering them alot, but i do have a good amp so that should help alot.)