PowerNaudio
10+ year member
the power of audio
well by the looks of it you have enogh room to put the subs on top of the box 2 subs side by side and then the other 2 right under and youll have about 8.5" left in between them. so using 3/4" mdf for the port that will allow you 2 ports of 3.875" in width x 13.5" high, and about 34" of port length fireing up on the same plane as the subs. with around 3.25cuft per two subs. that would give you a tuning of some where around 32Hz. these numbers are just aproximations and no acuracy to them but you get the idea. put the subs on the side or the top. wich ever gives the sub the most clearance in front of them, ill asume it would sound the best.
laters
so preaty much your same design but with actual values to them. lol
laters
so preaty much your same design but with actual values to them. lol