Yep, building a new house and HT, and I think I'm taking the IB plunge. HT room is fairly large, coming in around 7000 cu. ft. I've been perusing different drivers, doing a bit of research, trying to find what will make a good candidate for IB. Naturally, the AV15 and Tumult look very attractive. I can't help but think though that for IB, where enclosure size isn't really a concern, 2 AV15's for the price of 1 Tumult would be a better route to take. More displacement in the linear region it would seem. Any thoughts about the AV15's T/S characteristics and how that would work for IB is appreciated. My real question though is number of drivers. Again, 7000 cu. ft. How many AV15's (or other) would it take so that I never regret not having built a larger IB plenum/manifold? My first thought was "4 should be enough for anyone." Then I thought about how large the room really is, and thought "at $200 per driver, 8 would not be terribly expensive, and I can always upgrade amps later for more power." Now I'm thinking "maybe 6 will keep me from feeling really stupid." If the AV15's are dual 2ohm voice coils (like the Tumult and other contenders), then 4 would present a 4 ohm mono load (or 1 ohm with alternate DVC configuration). 8 would be an 8 ohm mono load (or 2 ohm). 6 would be a 6 ohm mono load (or 1.5 ohm). A mono 8 ohm is easier for most amps to drive. Thoughts?