@bkeske --
For me, it’s simple. I raise the volume to the point of the music, whatever it may be, sounds realistic and actually scales per the performance.
If it is louder, it seems artificial and too large, too quiet, the opposite.
Exactly. With some setups and speaker/acoustics combos the music "comes alive" at a relatively low volume level, but the scaling and overall presence would likely be off and need some more volume to fall into place. Low level listening and a sense of aliveness here is a great boon with late evening/night listening so not to disturb potential neighbors and/or sleeping family members, but for the music to more properly fill out the listening space - again, depending on personal preference, the material and recording nature - higher SPL's are necessitated.
More importantly however, IMHO, a speaker's advantageous abilities into low-level detail retrieval and sense of aliveness here isn't so much about being a benefit to low-level listening as it is to the way it affects average and higher volume levels and where it matters mostly - certainly insofar anything approaching a fuller experience matters; whatever accounts for this ability at lower SPL's isn't confined to this range alone, but brings with it a sense of "ignition" and live feel at higher volume levels as well.
I would say for most all, it is between 75-85 db. If louder, it typically means that it is still a realistic ‘size’ in my room.
That's about the average SPL range here as well, if occasionally a bit lower with music, and with movies somewhat higher in peak levels (but of course averaging lower).
What strikes me as a bit posh is the notion, if such is actually presented, that low-level listening is somehow a finer arts and cultivation to strive for with music reproduction in one's home. I'm all for preserving our hearing in these endeavors and not bombarding them with unnecessarily high average SPL's over longer durations, but fullness, proper dynamics, physicality and presence in reproduction has become curiously unfashionable starting decades ago, making you wonder if a live acoustical reference is really the overall goal in audiophilia.
John DeVore hits the nail on its head wonderfully precise here in his latest video blog: