Tyll probably meant to that a an equalized (be it diffuse or free field or whatever) measurement is such that the target response at the entrance of the ear canal (where the mic is located) is a flat line. The equalization is only valid for that head and torso and for a specific heading (free field) or an average of all possible headings (diffuse field) but basically representative of how an average person hears.

As Tyll said, it doesn't matter what headphone type it is and if it is partially seeing the effect of ear reflection or not. The bottom line is that this headphone or earphone must measure flat on that dummy's microphone (equalized response). If it's an iem, indeed it must somehow have filters or other mean to reproduce effect of outer ear artificially.

Worth noting these equalized target curves are magnitude only so even if you get there (flat target) you're not guaranteed to have won the battle (e.g phase may be all messed up).

Edited November 24, 201114 yr by arnaud

the target response at the entrance of the ear canal (where the mic is located) is a flat line.

Yup ... except the target response is at the eardrum in my case.

I'll also mention again that the HRTF I use is not idea, just the best I have.

The big point is being able to compare measurements ... which means always using the same curve.

OK. Got it now.