Initial Results for Head Acoustics HATS Measurements at Harman
I'm up against a bit of a wall here as I'm going on vacation next weekJohn Grandberg will have a headphone amp review going up, so stay tunedso I haven't been able to do all the number crunching I'd like. None the less, I'm far enough in to provide some cool graphs of the results so far.
The above plot shows the measurement of the room with a calibrated microphone at the listening position 40" above the ground. The smoothed line in the background is the Harman preferred listening curve. I did the measurements with this EQ as I wanted to measure the preferred sound of speakers with the head. I do have this measurement data, and later will provide views of the results both with this curve and with it subtracted, which would model a flat response.
In the above plot the light blue line is the average of all measurements made with both speakers running. The red plot is a moving average smoothed plot. I will be doing further number crunching on this data set to see if there's anything to be learned from angular changes.
Measurements with Left Speaker Only
The above plot shows the total averages of left and right ear measurements for the left speaker only. Notice the closer ear has the notch feature at 6-8kHz.
The above plot shows an average of all the azimuth measurements at the three different elevations. It seems the main effect of elevation change occurs in the 600Hz to 2kHz area.
Here's the interesting one: The above plot shows the average of the three elevation measurements at the various azimuth (left to right) angles. Here you can see a definite trend that as the head gets closer to straight on to the speaker, the dip at 6-8kHz and subsequent rise in treble gets higher.
I'll have a lot more to say about these plots in a couple of weeks after I get a chance to really digest them. I've also had a chat with Arnaudlong-time headphone enthusiast and hard-core audio measurement geekand he's going to do some curve fitting with tools I don't posses and should be able to aid in coming up with some useful smoothed curves. Perhaps to use to build a compensation curve for this head.
The tricky bit is figuring out what curve, or average of the curves above, should be used in compensating headphones. This is not a trivial question. For a start, on speakers you hear both speakers at each ear; with headphones you only hear the left channel in the left ear and the right channel in the right ear. Also, audio energy adds a bit differently in the room with both speakers going as opposed to just one. I think we're going to have to try a variety of curve compensations.
Once I've got some good prospective curves, I'll use them to compensate real headphone measurements so readers will have a chance to weigh in on which ones look most like the headphone sounds. Should be interesting.
I'd very much like to thank Sean Olive, Todd Welti, Henry Goldanski, Charles Sprinkle, Omid Khonsaripour, and any others who've help on the Harman team. This was a golden opportunity for InnerFidelity readers and myself...thank you! Also want to give a big shout out to Warren TenBrook who's been a big inspiration with his emails that stimulated this event and for showing up to add his comments and take pix. Thanks, mate.
Those of you who would like to download the spreadsheets from this DropBox folder.
Happy number crunching!