http://reaudio.com/speaker_box/LPort_Box_Calc.html Use this to see and create your box, very easy. what you need is to have a 10c/f box [after all displacements, such as port, subs, bracing,..] and you need port very big, say about 15"sq for every c/f of volume, so about 150"sq, can be a bit smaller. Try to make deep box, so back plate is far away from cone, you have now 17", make 23" or more if needed Hope this helps, Luka