The thing wrong could be about the first part of what I said. Which is that, even the 4620 is not accurate enough, resulting in different frequency responses after eq-ing. With distortion and phase-accuracy out of the way (which is the case with most decently made iems these days), there is really little else that could explain a noticeable difference in perception other than undetected frequency response differences. If they were the same frequency response at your eardrum, then it is literally impossible that a hissing noise is audible on one but not the other even after boosting the treble by 4db.That's the difference between theory and practice.
There are many members, especially in the ASR, who are of the opinion, that once we've talked about the FR and distortion, everything has been said.
I obviously don't agree with that.
Yesterday I compared the FH3 with the FH5s. Both were also adjusted to the 4620 preset.
And yes, of course, these two sound noticeably different.
But to be honest, I'm actually fed up with this fundamental discussion...