I have a friend who would like to make a portable bass system for his band (and I'm helping with the design). They play in smaller venues (no more than 200 person rooms) and would like something that they could cart around in the back of a van. I already know where to get the case hardware (metal corners, handles, etc.) but am interested in any design issues for pro audio. Here are some that I've come up with: - Sub must be sealed (things could be shoved down exposed ports) - Sub doesn't need to go extremely low (25-30Hz is the limit for the bass and drum?) - Sub needs to be durable (banging around in the back of a van on the way to gigs) - Sub must be capable of high SPL to fill the large room. - Sub will be passive (amp will be in equipment rack) Would a stack of 4 Tempests with a Q around .8->.9 do the trick? Would running a full stack of larger and smaller drivers be a better solution? Thoughts?