And to put a period at the end of these sentences…
There truly are only a few albums in my collection where the sub bass really stands out as a result of getting the phase correct.
And I have been collecting albums specifically with being able to hear when the phase IS correct, for decades now.
In fact I have a "phase" column in my JRiver player window just to note which tracks are in or out of phase.
And really only ≈ 10% of the albums I have, is where the bass is pronounced enough to be readily obvious when it's 'right'.
But when it is, and on one of those ≈10% tracks, it adds a whole nuther level to the visceral experience, which I find compelling enough to fuss with any of this in the first place.
And the setup of, and the system components I have running, all are chosen to fully enable 'proper' bass response down to at least 15Hz and functionally as it sits, it seems to reach close to 12Hz.
And of course these are subjective assessments since the only musical information that reaches this far down are impulse sources (drums, guns, cannons, lightening strikes, even the resonant drone of the air conditioning systems). And since they aren't 'steady state' taking a reliable frequency measurement is 'difficult'.
Even so when they whack one of those 6' drums it can 'light up' the resonance of the whole room.
But that's just where the changes to the sound starts, then as it dissipates and as the resonances 'play off' each other, this adds a rich source of additional acoustic nuances and subtleties, not to mention the kicks/thumps/whacks to the head which can also be felt in the chest.
I have a theory but with NO experimental data, at all.
So it's worth EXACTLY what you'd pay for it.
Even so, being able to have any system reach down this far, with 'authority', has additional SQ consequences as well, ones that are somewhat unexpected, unless you're familiar with what lurks down in the sub basement (there be dragons!).
JJ