Except Audyssey does not use PEQ. As I mentioned before, Editor App+Ratbuddyssey basically just allow you to force Audyssey to modify the filters created during auto setup. I believe it would work as follow:
- auto setup corrected the information from the mic in x number of positions, then based on the collected info created the filter to flatten the bass FR from say 15 to 100 Hz.
- Then reality check by REW/Umik-1 mic found a few dips and bumps, so you use the App with Ratbuddyssey to manually enter cuts and boosts to reshape the original target curve
- The new target curve won't be flat any more, but but it would then result in a flat (flatter curve in reality, when you do another reality check with REW.
In other words, it works like a cheating system. Audyssey use a target curve that is flat, it calculates and create filters that the logic/algorithm thinks will allow the FR to be corrected to flat. Unfortunately, likely due to the fact that the data collected are not not accurate enough because of the limitations of the mic's accuracy and capability, as well as the operators ability to select the placements for the mic, among other reason. So in order to achieve a flat/or much flatter FR, based on the after the fact results obtained by running REW sweeps, we manually enter additional data point in terms of cuts and boosts. It is like adding a feedback loop to Audyssey, except the feeback part is a manual process, that allow Audyssey REQ to have a second chance to sort of EQ the EQ'ed based on actual results.
The modified filters are still created by Audyssey based on the manual feedback data as described above; and are therefore still FIR based minimum phase filters, not the IIR based PEQ filters. There is no "Q" to worry about, just cuts and boosts of +1, -2 etc..at selected frequency points based on the REW plotts.