I just purchased a similar design from Martin Logan on clearance - though it only has 3 - 10" drivers it does put out a lot of clean output. Funny thing is with the drivers firing against each other the cabinet really does not vibrate. I am surprised more companies do not use this design.
Sys 1: Sherwood R-972, ML Stage center driven by XPA-1L, ML Purity L/R powered speakers, GoldenEar Invisa 525 height & MPX surrounds, ML Descent i sub, 2 Def Tech Supercube IIIs
Sys 2: Fusion 8100 driving small viewing room
In progress: Whole house audio built around AirPlay, a Sherbourn 18-45 and Axiom M-3s
Future Sys: Atmos/DTS:X for the basement - as many channels as I can afford! :-)
It may look impressive but it's really not. He's hitting 126dB with 40 or 50hz bumps. Selec was maxing our his meter with 2 x 18's in sealed boxes that cost under $1000 for drivers and amps...... Heck, you could max out the meter with 1 x 18 in a decent ported box.....
Still it's a nice room with some nice gear, just maxing out SPL meters means nothing though.
The dual Triax is impressive to me, but the video is not. I get where he was going with it, but I found it a little silly. No doubt those subs are freaking stupid awesome. I would love to feel the response in my living room.