Where is Mr. Dan Wiggins when you need him? And by the way, he is one smart son of a...! He pretty much laid to rest the myth of woofer speed/transient response vs. woofer size. After reading his technical paper and the "think-tank" battle on car sound & performance forums, i think i'm sold on his Tumult 15d2 driver. A sealed and L/T'd 1200 watt low Q enclosure. However, there is no place i can go to demo any of the high end sealed subs in the $2K+ range so i guess it all comes down to the various online forums. I would like to hear from "anyone" who has experienced the sound of the sealed 15" big-boys...ACI maestro, Revel b15, Kleiss s15a, Velodyne, Paradigm, etc. Anything subjective or objective, listening impressions, performance data...anything! Finally, a few more questions i'm pondering: 1. The musical differences in a critically damped sub (Q=.5) versus a bessel alignment (Q=.577) 2. The recommended f3 point for a sealed enclosure with a Linkwitz transform as it relates to room gain in a THX-select environment (1,800 cu. ft.). This room can be fully sealed. 3. The viability of a servo-circuit unit integrated into the sub. 4. The comparative levels of performance between the Tumult and those units mentioned above. My biggest fear is that this unit will overpower the room, hence the low Q alignment. But how low is the question. I would absolutely prefer a musical signature to this subwoofer, letting sheer displacement take care of HT. I have (3) 8" inch drivers moving the room currently so i don't fully know what to expect from this high end 15" driver. I do know that it models extremely well in winisd pro and Dan has made a very strong case for the XBL^2 topology, not to mention his "observations" on low inductance and transient response, which has put my mind at ease concerning the woofer speed myth. This guy has really accelerated my learning curve of loudspeakers. Now if we can just get the drivers released...smile Thanks to all.