This page keeps floating back up every so often. Very impressive work, and I can't argue with that sort of ambition. With that much space available, I personally would be looking at some other options that would have been a LOT easier to construct, but to each his own. As for some of the comments made above, some are rather ironic given that just last night I visited some friends over at Servodrive/Sound Physics Labs...
First to dkeller_NC, obviously you haven't experienced bass repoduction like that as in fact it is quite enjoyable, and makes it hard to hide the big grin it brings to most. Last night I again had the opportunity to briefly play with a PAIR of Contrabass subwoofers. These are FLAT to 14Hz, and can produce 116dB at 16Hz. Yes, they do music, not just produce sine waves, and were damn impresive on any of the music I had at hand. I had a chance to play the Telarc sampler "Jurassic Lunch" and I determined I NEED to get these in a real theater system to just experience them properly. I've been told the depth charge scene from U-571 is something to experience with these. For those who aren't familiar with the Contrabass, here is a link with some info.http://www.servodrive.com/servo/cb.shtml
On a mildly related issue, pronkie-uk mentions canceling out earthquakes. While not that ambitious, yesterday I read an article outlining how the Servodrive Bass-Tech 7 (the original DC-servomotor driven cone speaker) and the Unity TD-1 loudspeakers will be used for real world noise cancellation... to control the sound of commercial jets at an airport runway! Mind you to cancel sound, you need to generate nearly equivalent levels, and the acoustic consultants involved found the BassTech 7 and the TD-1 the ONLY products to actually meet the specs they had determined neccessary to accomplish the task! And to think I'm putting a relative of these horns in my home system http://www.avsforum.com/ubb/biggrin.gif
. Fun stuff, and again, there is NO problem at all with having 14Hz extension, and in fact, Tom Nousaine, noted subwoofer reviewer, constructed his personal home subwoofer which is capable of 120dB at 12Hz. The big problem at this sort of extreme is keeping items in your home in one piece if you ever decide to realy see what it can do.