According to Audyssey’s own admission, the Audyssey mics that ship with receivers are already calibrated to a pretty tight tolerance, so while Audyssey’s hand-calibrated mics offer some improvement, that improvement might be marginal.
While Audyssey does not let you have access to the calibration data, we are likely talking about +/- 1dB across the whole frequency spectrum (both in terms of frequency and amplitude response) as that is the tolerance the factory-calibrated mics are calibrated to… or are they?
The issue with response curves of the types of mics Audyssey – and pretty much everyone else – is including with AVRs is that the response curve changes dependent on the angle at which the mic is relative to the speakers’ drivers. This is why Audyssey – and AVR manufacturers – state that the microphone must be pointing straight up when completing the measurements.
However, the issue with this is that manufacturers assume that all your floor speakers are ear level, which is not always true and they simply ignore the fact that Atmos height channels are at a much sharper angle than your main speakers, and could reach as high as 0 degree angle – compared to the 90 degrees that ear-level speakers are compared to the microphone that’s pointed upwards.
The deviation between a 90 degree and 0 degree mic angle can reach around 2 – 4dB at 10kHz, 4 – 6dB at 15kHz and upto a crazy 7 – 10dB at 20kHz.
Therefore, as you can see, this is much more of an issue than trying to tidy up the mic response with a 90-degree calibration file with a tighter tolerance.
What Audyssey Could Do?
While I very much commend Audyssey for trying to push the envelope, as it stands now, the calibrated mic is not any more than paying for peace of mind. It is unlikely to result in a large performance difference compared to the stock mic.
I would like to see Audyssey offer both a 90 degree and 0 degree calibration file with the microphones and allow the user to specify the speaker angle in the MultEQ-X software per speaker. MultEQ-X can then figure out a better approximation of the calibration data that needs to be used for each speaker by interpolating between the two sets of data. This would yield a much more precise calibration, especially for speakers that are not at ear height – which are in fact most speakers in my own setup.
Audyssey could also allow people who have already bought the current microphones to create their own 0 degree calibration file by measuring the same speaker – e.g. the centre speaker – at a very close distance, such as 50cms, and compare the result between pointing the microphone at the speaker at 90 degrees and at 0 degree. This way they could calculate the required offset. While they would have to use smoothing to remove any errors, even this approximation could yield a much more accurate result.
They could even go one step further and use Yamaha’s approach for figuring out speaker angles. Yamaha’s YPAO uses a contraption which we euphemistically call the boomerang, that allows you to measure speaker angles for your speakers. Yamaha uses this data to feed into their DSP processing to allow for correct Yamaha sound-space processing for their own DSP programmes. (These programmes are awesome, btw, and I recommend you give them a go.) While this would require Audyssey to use something similar to Yamaha’s boomerang, it would allow for a more seamless experience, as opposed to entering speaker angles manually.