It seems we really do need a TL sub on the market. We were decorating the Christmas tree in our large open great room space on Saturday. My wife decided it was time for Christmas carols. So I put on a disc from Kings College on my DIY in wall system. That single 10" driver TL loaded filled the whole space uniformly with high spl, and authority. Yes, the bass pedals made our chests vibrate. It filled the space with clean deep bass with no sweat using little power. This convinced me yet again, this whole sub concept needs rethinking. That sub could also be placed behind pretty much any couch out of sight, as it has little depth. One 10" driver and no huge mega amps, filling a very large space and uniformly with no sweat or fuss with the highest quality clean low Q bass.
That basically harnesses technology that goes back over 2000 years to Greece and Old Byzantium. The more we think we know, the more we forget.