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In a recent thread, there was some question about the directionality of the Audyssey setup mic. Measurements were taken using the Audyssey setup mic supplied with the Onkyo TX-SR705 AVR, one of the little hockey puck mics with the raised center where the mic element sits. Here is the frequency response at different angles for that mic.

The 90 degree plot, black, is repeated above the rest of the plots just so it is easy to see exactly what it looks like. That 90 degree orientation is what we normally use, with the hockey puck horizontal and the element pointing toward the ceiling as it is supposed to be used. Frequency response (FR) rises dramatically above 2 kHz, but of course we know that there is compensation inside the AVR to give Audyssey whatever it is looking for.

The response at smaller angles is a little scary until you think about it. At close to the mic element's axis, 0 degrees through 45 degrees, there is some emphasis between 1 and 6 kHz. This means that sound coming down from the ceiling in that range is going to receive some measurement emphasis, and no doubt this is as the Odyssey engineers planned it. Sounds above 6 kHz at those angles are drastically rolled off. Above 10 kHz, where the curve goes way back up again, there is probably enough air and material absorption in most rooms that the amount of energy coming straight down from the ceiling is extremely small.

So basically the design appears to give some upper-room measurement emphasis between 1 and 6 kHz. This is good information for people like me who, for convenience, use a hanging microphone for general measurements. Even a good omni measurement mic will have some high frequency attenuation at 180 degrees. To be more accurate about our measurements, where Audyssey is concerned anyway, it would probably be best to have our measurement mics pointed to the ceiling so we at least are not de-emphasizing what the Audyssey calibration mic emphasizes.

At 180 degrees, there is, as one would expect, significant roll off above 4 kilohertz.

By the way, the dip at 180 Hz was due to floor reflection cancellation which I did not bother to try to overcome. Low frequency accuracy of these measurements should be pretty good except for at 180 Hz. Also, this is just for one model of the Audyssey setup mic, although it is reasonable to expect that the design tendencies we see here are probably universal across their different mic models, at least to some degree.
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