Yes, Audyssey is correct.

There is no table or lookup conversion because audyssey is correcting for phase. Each subwoofer will have it's own internal latency due to the onboard amplification\dsp and the mass of the driver. On top of this, where you put the subwoofer in the room in relation to the main R\L speakers will affect the phase offset too. Ideally subwoofers should be equidistant to your main speakers or symmetrical if you have 2. This is so that the phase of the subwoofer can be corrected to properly track both R\L channels.

Advancing the subwoofer (adding distance) shifts the phase positive in rotation. Retarding the subwoofer (subtracting distance) shifts the phase negative in rotation. Each shift is relative to the mains, that would be the reference signal.

[Linked Image from imgpile.com]

Borrowed from Wikipedia. It is showing the phase of 2 waveforms and relative shift. This shift can be expressed in degrees or time if it is a fixed frequency. To find the time length of a frequency divide 1000 by the frequency wanted. You will get the time of duration of the wave in ms.

80hz is 1000/80= 12.5ms per cycle. So to shift a 1/2 cycle you need to move 6.25ms or 7.087ft.

To measure phase you need a relative difference between 2 signals. The transfer function tool in audio tools lets you accomplish this with a built in sweep generator and pink noise. Or you can let Audyssey or Dirac do it for you.

The trouble is when you have multiple subs. It is best to phase align the subs to eachother first, then let the algorithm match them to your mains as one sub signal. Pretty cool when it works. Super tight and efficient output. High startle factor. laugh