What is the proper loudness for listening?

I have always asked the question if one can measure dynamics by a decibel number. There is a certain point in volume that makes the music come alive. You can hear the instrument separation, you can feel the kick drum punch you in the chest, and you can listen for hours with no fatigue. Yes the room, the room treatment, and the components will all play their part but I still think there is a low and high range you can measure that will always work and achieve that sweet dynamic sound stage or nirvana. 

Yes. Another way to say it is the optimal level is the loudest you can go for extended periods without risk of damaging hearing. Dynamic peaks in the mid to upper 80s db level starts to breach into that territory. A sound meter app like decibel on iPhone is your friend! When you start peaking in the yellow zone you are where you want to be in most cases ….. beyond the green and short of red.

optimal level totally depends on the situation... including other people in the room, your purpose, time of day, are you engaged in other activities, etc. ... and depends on the speakers, etc., too.

some speakers need to be "turned up" to come alive... I'd never want such speakers.  Others do very well at even quiet volumes; I'm constantly impressed by the dynamism and richness coming from the Klipsch Heresy at very low volumes, for example, and some of the most interesting listening experiences I've had with the Epi 100 over the years have been at low volumes late at night: they have clarity and sparkle.

@snilf Wrote:

Be aware, by the way, that "weighting" on SPL meters is crucial. Most are "A" weighted (note that the OSHA standard ditusa cites is given as "dBA").

See the tutorials below Decibel A, B and C:

Mike

https://www.engineeringtoolbox.com/decibel-d_59.html

https://www.vernier.com/til/3500

Thank you, @ditusa. These are very informative links.

Note that, according to your third link, "The A-weighted sound level discriminates against low frequencies.... In this setting, the meter primarily measures in the 500 to 10,000 Hz range. It is the weighting scale most commonly used for OSHA and DEQ regulatory measurements. The C-weighted sound level does not discriminate against low frequencies and measures uniformly over the frequency range of 30 to 10,000 Hz." This is just what I maintained in my earlier post, except that A-weighting actually cuts off at 500 Hz, rather than 100 Hz—which, of course, makes my point even more important.

However, I will admit to some puzzlement about the clause I elided: that A-weighting "discriminates against low frequencies, in a manner similar to the human ear." In my experience, audio system measurements are almost always given with C-weighting. Sometimes this is explicit, but even when the weighting filter is not specified, the numbers seem to be C-weighted. After all, we do certainly prize systems, and speakers, that produce sound below 500 Hz! To eliminate these sounds from the meter’s measurement because the human ear is less sensitive to them would not be what an audiophile would want to do. For one thing, low frequencies are felt as well as heard. Surely you (ditusa) are not advocating for measurements that ignore low—and high, for that matter—frequencies!

In any case, when I see the dB levels folks on this forum cite as preferred listening levels, and then try to match them on my system, I find that the higher levels (90 and above) MUST be C-weighted. My ears begin to bleed when I approach 90 dBA, but 90 dBC is just excitingly loud.