What is the proper loudness for listening?

I have learned that the best way for any system is to turn it up till it starts to get harsh, then turn the volume down till everything comes into FOCUS like a lens.You can tell pretty quickly. I heard a LOT of systems at AXPONA 2023 with my wife and we both thought most systems we heard were too loud for the room. But, there are people coming in and out, talking, etc. So it is limited to say the least.

                             How LARGE do you like your music?

     Unless a system can cleanly reproduce all the information (well engineered/recorded in an environment with good acoustics and mic placement) in a quality cut, to the original/intended dB level; It's listener will never hear that information.

              ie, regarding, "depth": the reflection off the venue's back wall.

      Of course: familiarity with the venue in which a recording was made,  would go a long way with regards to recognizing whether what one's hearing is actually accurate.    NOT that that's a necessity, when it comes to the enjoyment of one's music, BUT- having that knowledge, one can be confident that their other recordings are also being faithfully reproduced.

       'Checkerboard Lounge Live Chicago 1981' (on vinyl) is a favorite of mine, far as being able to hear the room, especially between songs.

        Especially, in the softer cuts of Diana Krall's 'Live in Paris' vinyl (45 RPM/180 Gram), I find the Olympia Theatre's back wall reflections nicely reproduced (with accurate depth).

         Back the the size-of-your-music thing: I turn my sound up slowly (a song at a time, to acclimate the ears to higher dB levels, without having them shut down), until my image height reflects where I imagine/know the performers to have been, when recorded.     Again: a system has to be able to reach that level cleanly/without distortion, or: it's just LOUD (iow: noise).

        It's been my experience: seated in the better/more expensive, front and center seats; it's easy to hear and locate individual voices (human or instrumental), on a stage and seldom would the level be low enough for some to consider, "safe enough".     Yet: no one complains, because it's clean sound (just big).

                    OF COURSE: different strokes, for different folks.

                                          Happy listening!

I've found that Paul McGowan has a point: especially with acoustic music (solo, unamplified voice; solo acoustic instruments or small ensembles; piano), the volume usually sounds best when it reproduces accurately the volume that instrument would produce in your environment. Therefore, even a piano can easily be played too loud; if your room is small, a grand piano would overwhelm it, and not just by taking up too much space. One of the things a good audio system should do is to accurately recreate the size of the instruments being played. Perceived size is not entirely a matter of SPL, but they are correlated.

When it comes to amplified music (rock, most jazz, electronic, etc.), this principle is harder to apply. As long as your amp isn't driven into clipping and the high frequencies still sound sweet, your pain threshold is about right for a band like Tool or Massive Attack. After all, that's where the volume would be in a live show.

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"). Most laptop SPL meters I've seen, and most inexpensive hand-held meters on eBay or Amazon, are ONLY "A" weighted. What this means is that frequencies below 100 Hz are NOT registered at all! So if you're listening at, say, 70 dB with an "A" weighted SPL meter, you're probably hearing music that would measure 80-90 dB in "C" weighting, or even more. I learned this the hard way.

I like 70  to 85 dB.  Does not sound as good and feels pushed on me if it gets louder.  

When instrument volume sounds like what your hear it to be like in a live environment?  Except for rock concerts which may be detrimental to your hearing at the supposed actual volume.

Some approximations are below.

Generally, an acoustic guitar will put out between 70 and 90 decibels.

Piano (normal practice): 60 to 70 db. Piano (fortissimo): 84 to 103 db. Oboe: 90 to 94 db.

Cello ranges from 82-92 dB.

Violin ranges from 84-103 dB.

Chamber music in a small auditorium range from 75-85 dB.

The trumpet can range between 80 and 110 decibels, while the trombone can peak at around 115 decibels.

A drum set and cymbals is 119 dB loud on average but can range between 90 and 130dB (decibels) depending on what instruments are being played.

Generally, 75db is more than enough for me in my room, which is still on the way to being better treated.  Once it is treated properly, I may change my mind.