If you are going to a ported or bandpass box it really needs to be designed for you particular speaker and what you want ie where you want it to hit at. A bandpass will make your speakers REALLY efficient however it tends to be at one freq and usally doens't sound the best. You can also blow your speakers easily if not properly set up. same thing with ported. Both ported and bp are sesitive to volume chagnes so make sure you accurate if you are going to build a box. I think twice the cone area = 3 db's with the same power.