How loud is loud?

Seems like a rhetorical question, but I'm curious what other folks think is "ok, now that's loud"

For me, if something's hitting 100dB as measured from where I'm seated while listening, and not just for a brief moments, but with some regularity, that's loud.

I used to listen at higher average volume than I do these days. Typically, I'm finding that at the right volume, the recording is more nuanced then when it's running full throttle.

If I'm not mistaken, the late Peter Walker observed that every recording has it's one correct or optimum playback level. I think generally he was correct, though once we are willing to forge optimum there's a range of acceptable.
Wrong details like this drive me crazy at work!
Then here is another one.
dB/W/m is an efficiency spec.
Actually, that is the sensitivity spec. And yes, I know many seemed to be confused about this, and even some manufacturers list it as efficiency, however here is the difference, Efficiency vs. Sensitivity.
Hi Mulveling,
Ok, guilty as charged, you're right it is a simple topic regarding loudness
and nothing more. I do understand Bombaywalla's post in the technical
sense as he presented it. I have no intention to muddy the waters and
introduce chaos.
I do see a reason for the ganging up.

Here is a link from Wiki,

"The distance of the measuring microphone from a sound source is often omitted when SPL measurements are quoted, making the data useless. In the case of ambient environmental measurements of "background" noise, distance need not be quoted as no single source is present, but when measuring the noise level of a specific piece of equipment the distance should always be stated. A distance of one metre (1 m) from the source is a frequently used standard distance. Because of the effects of reflected noise within a closed room, the use of an anechoic chamber allows for sound to be comparable to measurements made in a free field environment."
08-20-14: Atmasphere
The cleaner your system is, the less loud it will seem.
Very true. And I would add that the cleaner the recording is, the less loud it will seem. IMO/IME very high quality recordings can be, and will in fact tend to be, played much louder than run of the mill or poor recordings before seeming to be "too loud."
08-20-14: Bombaywalla
SPL drops approx 3dB for every doubling of the distance.
For conventional box-type (non-planar) speakers, other than perhaps tall line-source arrays, that would actually be 6 dB per doubling of distance. I can write up a paragraph or two explaining why, if anyone is interested. The number for planar speakers is significantly less than 6 db per doubling of distance, and I believe will vary significantly depending on the speaker's height.

Addressing the original question, for the classical music which comprises most of my listening I generally find myself listening at average SPLs that are in the 70's at the listening position, with very soft notes being around 50, and brief dynamic peaks on well recorded minimally compressed symphonic music reaching about 100 to 105 db.

Sustained levels start to seem "too loud" somewhere in the 80's or high 70's, for most of the recordings I listen to. Although those numbers would be way higher for something like the "Sheffield Track Record," which I have in my collection.

All of that is at the listening position. I agree that listening distance is irrelevant to the discussion, as is the Wikipedia paragraph quoted above. I'm surprised there is any disagreement about that, especially given the reference in the OP to SPL "as measured from where I'm seated while listening."

-- Al