@atmasphere --
"Its just physics, physiology and its not my theory- its that of Dr. Earl Geddes IIRC."
I'm aware of that. By "your theory" I simply implied that you presented it.
"I'm not certain of what you are trying to say in parenthesis."
That was a bit elusive, yes. I tried to touch upon that using a sub setup the way I outlined as being my preference is a matter of having a different "design" goal - i.e.: high-passing the mains fairly high to a pair of subs, (the need for) symmetrical subs placement, high sensitivity, pro drivers, very large overall size and usually not direct radiation - all in the service of loads of headroom in the lower frequencies (that translates into easy of reproduction and very low distortion) and optimum integration.
"If you are careful with placement, you can get good bass at the listening position with only two subs."
Indeed.
"In my case, having done many installations at shows and the like over the last three decades, I've found the DBA to be a nice solution for a vexing problem of getting the bass to play properly where the listeners will be sitting."
Makes sense, and not least over a wider listening area for more people to enjoy a fairly smooth sounding presentation in the lower octaves.
"I recommend the Swarm becuase its designed to be as innocuous as possible. Its also reasonably priced. I've no financial association."
The Swarm a la Duke is no doubt a capable solution, but for high efficiency main speaker designs there are compelling reasons to go high eff. with the subs as well, and that requires very big size - plain and simply. It's not a requirement that sells well in audiophilia in general, but sonically I'd say it's a necessity in this particular context. DBA with high eff. subs is an option as well and just a scaled up Swarm, if you would. Maintaining symmetry of placement, be that with pairs or DBA, is paramount to my ears.
"Having recorded a number of LPs, some of which I mastered myself, its nice to be able to compare to my own expericence of having been there when the recording was made. If you can better that reproduction as you seem to be claiming, I'd love to hear it."
I don't know if that's my claim other than recommending another viable subs option, but what I'm advocating would certainly be benefitial into vital aspects of live acoustic music reproduction as well as other genres - again, not least in the context of coupling to high eff. main speakers.