Alan:
I am building one this year. I have put probably 50 or 60 hours of research into the design of the these subs. Positioning is just like for a box. Play bass tones at your listening position, check your SPL at your wall locations and pick the best location for the hole. I am going to use 4 15" drivers with a prosound amp and a BFD for equalization. I have seen many people post charts of their IBs showing flat frequency response down to less than 10 Hz. Many people in the know insist IB bass is the best you can get, unless you want to spend 10 times more money. My entire setup, including driver, amp, Behringer BFD, and construction materials will be less than $1000.
There are many threads at www.hometheatertalk.com expounding on the virtues of IB bass, in addition to the Cult, which was previously mentioned.
Pete
