TIma, it's not about room correction at all.
It is about trying to correlate a measurement with what makes music sound "harsh & bright & objectionable" to my ears .
In my case it's a FR bump in the 4-6kHz region. (The dsp is not the protagonist, it's a tool)
Your quite right that bumps in the 3.5- 5 kHz zone are to our Ears very sensitive corresponding to the resonance frequency of the ear canal a second peak at 13.5 kHz which is thought to be the 3rd Harmonic of the resonance
our perception of sound is a combination of on and off axis responses/reflections
however there is also as well described by JA what our ears “hook onto” in a speakers response
my own work with crossovers this past year has demonstrated to me at least that one needs to look at bass and mid bass balance to any high-frequency alterations, it’s not all about one octave on its own
its part of my natural sound learning experience that these factors are important , but probably a subset of this discussion which is conceptual rather than operational/electromechanical
speakers that I have encountered which seem intrinsically natural get this balance correct , I have found a number of “Hifi” speakers emphases the treble as a “gotcha interested in the showroom “ effect, but this is well known and I am not the first to appreciate this frequency balance issue it tends to undernourish the midrange and make the bass appear to be less and boring in the long term
where acoustic listening helps me, is in listening to violin as a real test.
firstly there is a problem recording the violin around 3.5-4khz if memory serves where there are some “aggressive harmonics”
but I need to hear it’s not harsh in any way, and the resin, and wooden body of the instrument are present but don’t dominate stradivarius should clearly sound different more brilliant in harmonics than Guarneri which has a darker richer midrange and woodier hues compare Ray Chen to Augustine Hadelich ( note Hadelich earlier recordings are with Strads, see Paganini caprices)
It should not sound boxy or shrill or favour certain strings, pizzicato should have an attack with some wood decay