Behringer Ultra-Pro PEQ2200 User Manual page 14

6.2 On phase shift and time delay
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Please also note that filters show a natural tendency to produce a “ringing” sound as their
bandwidth is narrowed, an effect that is caused by system-intrinsic noise modulation that
occurs with any kind of filter. It is therefore recommended that you set all filters not in use to a
mid-travel position or simply switch them off to minimize these side effects as effectively as
possible.
6.3 Using a frequency analyzer