so im going to be buying 2 Fi bl's 12". im thinking 2.5 cubes per a sub since there gonna be runnin off a single aq2200d amp. so what should i do about the port. im thinking around 70 sq" of port which would be 4.6 inches wide. what are ur suggestions for a box that would run this set up well?

Stay within Fi specs for box and tuning and you should be ok.

Are you doing two seperate chambers or 1 common chamber for the pair? Your right on in your ^2 of 12-16" per cubic feet of air space.

well there specs are 2.5 max for each sub an im thinkin 2 seperate chambers for each. except idk what to tune it at. idk what these subs do well at

I think I just saw this topic on the12volt. Anyway, as said above, go with what Fi suggests. Few companies come close in testing and design to Fi. 70 sq" of port sounds like a good start. I think you will be fine with a 5 cube box (after displacement) with a single chamber. Just build it strong.