Why does GLM AutoCal2 use filters with positive gain?
The main reason is the very large number of real-life in-room frequency responses we have collected and analyzed over the years.
These have teached us that a significant advantage can be achieved in many cases with the type of positive gain offered by AutoCal2. It is quite common in many rooms to see a low-Q notch in the range 100...300 Hz. We have analyzed and come to the conclusion that the combination of positive gain used with other compensations in AutoCal2 results in a more efficient compensation for the room effect without compromising either the quality of audio or the maximum SPL delivered by the monitoring system. There is a monitor model specific restrictions to the gain, Q-value and frequency range of the positive gain filter to avoid possible issues when using positive gain.