Getting Ready to Measure My Head at Harman's Labs
Thursday I will be at Harman's research laboratories to measure what my head hears when in front of a very highly calibrated speaker system. It's an effort to drill into the measurements and, slowly but surely, come to a better understanding of what's going on.
If you want to catch up, it started with my Audeze LCD4 review. Then Audeze brought to my attention that these so-called calibrated heads measure differently one from the other. Pretty convincing stuff, so I started looking into what I might do to investigate the issue. Then Warren TenBrook stirred the pot with a very interesting email exchange with myself and Sean Olive. And that got me thinking: Since the premise Harman target response curve is that headphones should be tuned like good speakers in a good room, wouldn't it be a good idea to have a look at what my head, in particular (since it's the one used for the 800 or so measurements in the InnerFidelity headphone measurement database), hears when in front of a good speaker system? Since I have to go to L.A. for T.H.E. Show Newport next weekend, I asked Sean Olive if he would allow me to measure my head as part of the trip. He very graciously agreed.
And then I got to thinking, Geez, I'm not really set up to measure speakers with my head...I better do some cogitating and get this figured out in advance.
The first step was to mount the head on a tripod...that turned out fairly easy. I won't bore you with details. The next bit is more complicated. I will be measuring the head's response at a number of angles and will then average all the responses to get some spatial averaging to smooth things out a bit.
I started with paper and cardboard models as you can see from the above photo. The result was the little gizmo you see below.
It allows me to set the azimuth and elevation fairly precisely. I'll be taking 15 measurements; 0, +/-10, and +/-20 degrees in azimuth, and 0 and +/-10 degrees in elevation. I'll be doing that with the speakers driven in stereo, but I'll also be repeating the measurements with only one channel driven in case there might be some differences worth note.
Here's the result of the dry run at my house with some pretty middle of the road speakers a friend built for me a long time ago, measuring at the 15 angles, averaging them all together, and then smoothing the data.
I was surprised it came out as well as it did. Big notch at 45Hz is probably a room mode. The peak at 3.5kHz from the concha bowl is right where it should be, but the run-up from about 600Hz to 2kHz is flat when it should be rising gently. This could be the speakers, but I've got a hunch that it actually may be from the fact that my head has no torso, and that rise is, in part, due to the presence of a torso. I suppose we'll know more after the measurements this Thursday.
Anyway, stay tuned, I'll post the results (and spreadsheets for all you math geeks) next week.