You are quoting subjective studies resulting in an objective statement.
I agree - the studies are subjective, and that's the best we have at the moment. (can you think of a way to do this kind of study in a purely objective
way?) Just because it is subjective does not mean it is not a scientific study. As the Wiki page says, the studies have resulted in an international standard: ISO 226:2003 Acoustics -- Normal equal-loudness-level contours
There are popular "studio monitors" now that do this to make people happy. Sell products. They are no longer "studio monitors".
You are talking as if these studio monitors cannot have the feature disabled. Is that the case? If so, I totally agree - they are no longer monitors, and I would definitely not buy them. It would be quite bizarre if the feature could not be disabled. (btw, it can be disabled on the CLP-430)
The studies also do not worry about the fact that many people have lousy hearing.
I'm not totally convinced that this is all that relevant. The feature simply tries to make sounds of different volumes have the same perceived tonal balance. So, if a person with lousy hearing hears music at a loud level a certain way (in regards to EQ), then when they reduce the volume, they will experience the same tonal balance as before. Yes, if they have lousy hearing, the tone they hear at BOTH sound levels will not be the same as someone with normal hearing. Conceivably, these people with lousy hearing would perhaps be able to apply a static EQ to compensate for their hearing deficiencies, and the equal-loudness-contour EQ could work over the top of that. I might be wrong though - perhaps it all falls in a heap with people with hearing loss. However, even if it is not as effective, it may not be all that detremental either.
All you have to do is listen to a high quality sound system with 200 watts per channel at low volume. By this I mean low enough for you to carry on a conversation with others in the room without raising your voice. You will find out real quick how much lack of bass there is in many amplification systems at low volume.
Perhaps it is less necessary with high quality sound systems, yes. However, even with these high quality systems, in order to perceive the same
tone at soft levels as loud levels, the same EQ adjustment would need to be applied. The tone at low levels probably does sound more pleasing than it does on a poor system, but the whole idea is to make the perceived sound at two difference listening levels sound as close as possible to one another.
I agree - it would not always be appropriate to do the processing. One example I can think of would be a movie soundtrack, where the producers have a good idea what sound level the audience will be listening at. They may well optimize the EQ for the sound level at any point in the movie, such that no further processing is required.EDIT:
This actually is not a good example, because even for this case, if we happened to listen to the movie at a rather low average level (lower than envisioned by the producer), it would still be valid to apply the EQ correction. I came across a system that can do the EQ adjustments on the fly, according to the level at any point in time - that kind of system may well not be appropriate for a movie. In fact, I don't like the idea of applying this type of correction in a dynamic fashion.