In the thread in this forum on the AES2012 paper about perception and measurement of headphone sound quality, I asked the Harman research team whether they have considered measuring desired headphone frequency response using loudspeaker playback on a dummy head as reference, similar to what is done by the Smyth Research Realiser A8.
Well, I've taken up the task myself, using binaural microphones in my own head, measuring in-room using Room EQ Wizard 5.0. The microphones used are the in-ear binaural microphones Sound Professionals MS-TFB-2, which when mounted, allows over-ear headphones to be worn as usual. Loudspeakers used are Revel Salon 2 in a smallish room. Note that neither the frequency response of the microphones nor loudspeakers matter, since we will only care about relative differences.
To be precise, the measurements are as follows:
a) Measure in-room response of loudspeakers, using binaural microphones mounted on stand.
b) Measure in-room response of loudspeakers, using binaural microphones mounted in ear.
c) Measure response of headphones when worn over binaural microphones mounted in ear.
- Subtracting (a)-(b) gets us the HRTF of my head in-room, at least in terms of frequency response.
- If our speakers and room were both ideal, then we would like our headphones to have a response such that (c) is equal to (b).
For spatial averaging to minimize comb filtering effects, I took measurements of (a) and (b) in each of 3 locations: center, and 15 degrees to the left and right. Okay okay, I didn't really measure 15 degrees exactly.
Here are the 3 curves for (a), after 1/6-octave smoothing:
Similarly, here are the 3 curves for (b):
The REW software doesn't support averaging the curves, so here are the right15 curves superimposed on each other:
Red curve is free standing, green curve is in-ear.
Continued next post.
Edited by JMS - 12/19/12 at 1:24pm