First of all, want to make clear that I understand why we measure the amplitude of a headphone on an ear-canal.
What we must not forget, is the fact that that hump around 4-5kHz is not a property of the headphone itself but is an effect of measuring at the earcanal.
The headphone should be more or less flat in that area. This is also what Sean Olive said in a interview.
(Questions starts at 1:40, quotation at 2:30)
But the earcanal not only amplifies certain frequencies (due to resonances or reflections), it also changes the phase, again due to resonances an reflections.
While its nice to look at an graph with an actual and ideal frequency response, there is no 'ideal impulse response' on an ear canal fixture as well as an ideal group delay /phase response.
The pinna's and the ear canal's phase transfer function is just overrules the one of the headphone itself, but still, th eheadphone's phase is of our interest.
(I know headphone itself is critical to say)
To make visible what I am trying to say, I made two measurement of the same headphone (k702)
One of them is an a flat plate and one of them on a self made ear-fixture which is not accurate in any way since I don't have a targent curve.
Magnitude of botch measurements, only to get an impression:
View attachment 155736
Impulse response of the measurement of k702 on ear-fixture:
View attachment 155737
Impulse response of the measurement of k702 on flat plate:
View attachment 155738
Phase measurement of k702 on ear-fixture:
View attachment 155739
Phase measurement of k702 on flat plate:
View attachment 155740
As seen in the pictures, the impulse response and the phase, which are both in our interest, are manipulated by the ear-fixture in a big way.
That's why I came to the conclusio, that for those measurements a different fixture, or at least a different sound pressure sensor does make sense.
I wanted to post this, not because I want to tell anybody that he is false and I am right, I just really like the scientific approach of this community has and thought we can have an interesting discussion without making suggestions to each other about any readings we have to do.
Actually I do some readings right now for the research at my university.
I really admire your work Amir, if I made a wrong impression on that.