I agree with what you're saying but to me, what you're describing is people using the term "neutral" who don't understand what it means. Neutral is not a 100% subjective term, it has a relatively precise meaning. I also agree that giving it an absolutely precise meaning would clear up some forum discussions quite a bit but at the same time, if we're going to be honest about how audio works in practice, then we're going to need a new term to replace "neutral" and with that new term we're effectively back to square one again. Having said this, there is to some degree an avoidance of honesty here on head-fi, even to an extent here in the science forum. That's to be expected though, this is after all a site devoted to headphones/headphone related equipment.
If we are going to be honest or at least strive to be, then as you effectively say, the vast majority (probably even more than 99.9%) of the time "neutral" would NOT be a term applicable to headphones. One of the misconceptions I see here quite frequently (or if not a misconception then a least a fact somewhat "swept under the rug") is that even if a set of headphones existed with a perfectly linear frequency response, they would still NOT generally be "neutral", for two different, though related, reasons:
1. The stereo image is presented very differently with headphones than with speakers, as are bass frequencies.
2. Commercial recordings are generally not created in linear environments and are not designed to be reproduced (played) in linear environments.
Point #1 appears to be well known/appreciated, although somewhat swept under the rug, whereas point #2 seems to be a more common actual misconception. There are quite a few threads, even in this sub-forum, regarding the pursuit of linearity, which in some parts of the recording/playback chain is entirely desirable but in others is only desirable to a very limited extent. In these parts of the chain, typically the transducers, neutrality is what's important, NOT linearity! IME here on Head-fi, the most common issue/problem is not the misuse of the term "neutral" but of the term "reference" or at least, of what people use as a reference. For some reason I don't understand, the production (recording, mixing and mastering) of the material being listened to is largely or at least significantly ignored which is bizarre because this IS the reference. Excepting just one or two terms (such as linear), no other terms (including neutral) have any meaning at all without considering the reference and the production of that reference. Let me give an example:
1. Who here would consider Beats headphones to be linear? .... - Hopefully no one!
2. Who here would consider Beats headphones to be neutral? .... - Probably no one again but, I contend that that view is not necessarily true, it all depends on the production of the reference! Let's say the person/s who created the recording (inc. mixing/mastering) did so on Beats headphones. As far as someone playing back this reference is concerned, Beats headphones would in fact be the most "neutral" headphones on the planet and your far more linear headphones would be proportionately less "neutral".
More generally, headphones can only really be described as "neutral" when playing back material specifically mixed for headphones and even then, the degree of neutrality would depend on the frequency response of your headphones relative to the headphones the mix was created with. There appears to be an assumption, even here in the science forum, that linear is the reference to aspire to but I contend that's only desirable up to a point, beyond that point, the search for linearity is just as likely to actually take us further away from neutrality.
G
