Hello douglas_schroeder,
I have never employed 4 to 12 15" woofers in my room or systems in different configurations of large drivers reaching down well below 20 Hz. I've only employed a maximum of 4 10" woofers/subs in a single optimized configuration, that reach down to 20 Hz, but not likely much deeper, and were included in the Audio Kinesis Debra 4-sub distributed bass array (DBA) system I've been utilizing in my room and systems for the past 5 years.
Since employing the AK Debra 4-sub DBA system, however, I have become very familiar in experiencing and enjoying very high quality bass performance that you very aptly describe as having the qualities of "gradations of power, dynamics, smoothness, ease, tonality, etc." I would only suggest adding speed, accuracy, detail and naturalness to your list.
But your apparent endorsement of employing subs with larger woofers and in quantities beyond 4 subs to reproduce bass well below 20 Hz and even further improve bass performance, both surprises and somewhat confuses me.
It's my understanding that reproduced bass tones below 20 Hz are not audible, mainly just vibrate things around the room including parts of our bodies, there are very few musical instruments that produce bass below 20 Hz with pipe organs being the only ones I'm aware of and there being virtually no commercially available music recordings containing bass frequencies below 20 Hz.
I prefer bass that sounds and feels natural like when music is played, heard and felt live in person at smaller venues, not like over-amplified arena rock bass. What am I misunderstanding about music bass below 20Hz?
Thanks,
Tim