>>bridgeman, how did you come up with the 94hz?
I plugged 18x12 (and guessed at 8 foot height) into MODECALC, a little DOS room mode calculator you can download from the realtraps site. 18 x 12 is a pretty decent size so the room modes are spread out nicely (a 7 foot ceiling would be perfect, I think) and 94 Hz was the first point where the modes started to pile up on each other... 18 feet gives you peaks at 31, 62, 94, 124, 155... Hz, while 12 feet gives you peaks at 47, 94, 141 Hz etc...
Modecalc only shows you the peaks not the dips but it's a good start and easy to use. Free is nice too
