OK here's what I did, I took a single 12 in a sealed box and ran a sweep, term lab said my res freq was 49 hz, so I built the box with 16.15 in^2 of port per ft^3 of net volume for an (18") and tuned to 46, and it worked out good my peak is 49hz, I would try and track down someone with a TL and start there, spl boxes are normally fairly small (around mins for sub spec) lots of port, lots of power.