measure with microphones located in the concha.
They'll have to be at least flush with the ear canal entrance to get reasonably useful results past 3kHz or so in my experience - so not in the concha
.
Is there a harman curve for over-ears without the ear canal effect to be down-loaded somewhere?
If your goal is to perform in-ear measurements and
directly compare them with the Harman target
minus ear canal effect, I can see a few potential problems here. My understanding of these notions is incomplete, so don't hesitate to correct me here.
From that article (which you can find without paywall) :
https://www.researchgate.net/public...mmission_From_Sound_Sources_Close_to_the_Ears
From what I understand what you see here is the difference between measurements done at the blocked ear canal entrance (EEP ?) of the ear simulator and measurements done with the ear simulator with its own microphones (at DRP ?).
You see a peak centred around the ear simulator's canal resonance that drops back to zero at around 5-6kHz (let's for now not bother with the data above 7kHz, that's a whole another kettle of fish). This matches pretty well this (idealised ?) representation of the overall gain we experience, that you've probably already seen :
The thing though, this figure only shows the transfer function between ear canal entrance and DRP for that particular fixture (which I believe isn't the G.R.A.S. used by Harman's research). So you probably shouldn't directly use that figure's data and apply it to the Harman target to get Harman minus ear canal effect. The "gist" of it, however, ie the peak centred at the ear canal resonance, that drops back to zero at 5-6kHz, might be a useful visual guide to follow.
Besides, your own ears are not similar to Harman's ear simulator. If your own head had been in the place of Harman's mannequin in their reference room, the same methodology Harman used to determine their target would have resulted in a more or less different target, particularly at higher frequencies. So you wouldn't be able to directly compare them.
Finally, you have to make sure that your in-ear mics are properly compensated. What properly means here, I have no idea ! I occasionally compensate my own in-ear mics against a UMIK-1 with a speaker in very near-field-ish conditions. Even when limiting myself to frequencies below 800Hz or so there still are moderate differences with Harman's target. Is it because my UMIK-1 isn't perfectly compensated ? Is it because my compensation methodology is flawed ? No idea.
So, what you should rather strive to achieve is not to directly compare your own in-ear measurements with the Harman target minus ear canal effect, but rather first and foremost try to determine
what the Harman target would measure like on your own head, with your own microphones, and then only compare your individual HPs measurements with this "individualised Harman target".
A few things you could do :
- below 800Hz or so : buy a pair of ANC headphones with a solid feedback mechanism, no volume dependent EQ, and tight tolerances. These will always strive to deliver the exact same FR in the range where the feedback mechanism operates regardless of most coupling issues (illustration of that phenomenon
here). This makes them very good "translators" between ear simulators and your own in-ear mics.
- above 800Hz or so, this is a lot trickier. You might want to read
that post I wrote a little while ago on the subject. You may buy a whole bunch of headphones (preferably ones with known good properties to translate well from ear simulators to real heads, ex large open dynamics such as the HD650), that you equalise to Harman, either via presets, or better, by sending your own samples to people owning a Harman compliant fixture (ex : Oratory). Then measure these on your own head, and average the results. This should give you a
rough idea of what the Harman target should measure like on your own head, with your own mics. Emphasis here on "rough" : the average of the headphones equalised according to Oratory's presets is not a perfect match for the average of the Harman headphones I've also measured, and its shape in the ear canal gain region is... not what I'd expect (if I were to apply the "gist" of Hammershøi and Møller's figure above). So I doubt that it's a perfect representation of what the Harman target would measure like on my own head. Note, in addition to these difficulties, that blocked ear canal microphones may show some moderate inaccuracies above 2kHz or so and that above 7kHz they may get more significant.
You may PM Mad_Economist about in-ear measurements, he knows a lot more than I do on these matters and unlike me actually has solid theoretical knowledge
.