The SPL level for best listening is an area I have been exploring lately, and have no definitive answer. I can only comment on what I have observed.
The first thing I will note is that reader reports of what level they listen at are not a very good reference point. I say this since there is no real mention of whether that is with a calibrated SPL meter and where it was placed. Also seldom a mention of what measurement curve is used for the report. Have to assume that most are using dbA unless otherwise specified.
I am in an apartment so tend to pay more attention to it than many. Recently had a neighbor that was very sensitive to certain frequencies which made it a real exercise in trying to control volume. My environment is also terrible to use as a reference since the noise floor tends to be about 30 dbA. At times up to 40 dbA.
I have been changing some components so have been tracking that in relation to how the music sounds to me at different levels. In general quick usage I am using the NIOSH SPL app on an iPhone with the built in mic set to dbA. I have also tried dbC and find that if I feel the sound is well balanced at any level, the difference is negligible (1-2 db). If the music sounds unbalanced to me the difference can be 3-5 db between the 2 calibrations. I have also noticed a difference that I can only describe subjectively. If the overall sound to me is congested the SPL will read quite a bit higher - I have to push closer to 90 dbA to enjoy the presentation. I feel that this is most likely too much emphasis across a mid range frequency spread with poor decay, resonance and harmonics in that spread. Could also be poor decay, resonance and harmonics in the lower frequency; I haven’t done frequency analysis/waterfalls to isolate this. When I am most happy with the music presentation I find that I can listen and enjoy the music at 70 dbA, and that 80 dbA is life like enough for me. So what is the music presentation that I enjoy? A perception of width and depth to the sound stage. That any singer, singing is in front of the rest of the sounds presented. That drums and percussive instruments are behind the other sounds presented. Natural sound of individual instruments is important, but to me that matters less than the sound stage balance. Obviously the presentation that I like is not the same with every composition. Singer songwriter, jazz ensemble, funk, hard rock, classic rock, big band, chamber music, full orchestra all have different depths and spreads, but as long as the sound stage is balanced I can enjoy the composition.
I do have a calibrated mic and REW to refine my sound analysis and to double check the relative readings that I get with the phone app, but haven’t done that yet. Need to have the wife out for a while to set up and do that properly. In conclusion, to me 70-80 dbA with the phone app is plenty even with a high noise floor. I might even enjoy it at lower volume if the noise floor were lower.
