In the Zu Definition 4, the sub-bass amp includes:
1/ an output volume setting;
2/ a low pass filter frequency setting to define the hinge point for the filter;
3/ a phase setting in degrees;
4/ a PEQ frequency setting;
5/ a PEQ gain setting.
The PEQ, or "Parametric EQ" functions differently than the more widely understood "Graphic EQ." In the Def4's case, the PEQ frequency setting allows you to shift a reference frequency for boost contouring, up or down within the range of 20Hz - 50Hz. The boost applies on an 18db/octave curve *below* the selected PEQ Frequency. Separate from the low pass filter frequency setting which determines the frequency below which the sub is active, PEQ allows you to manually address room effects in the deep bass region where most residential listening rooms suffer suckout. Once you've selected the frequency that best allows you to ameliorate your particular room's bass anomalies, the PEQ Gain control allows you to dial-in boost, in this case from 0 - 6db. Cut is not in the mix. However, Zu ships Def4 with the PEQ Gain dial at its mid-point (+3.0db), so effectively if you start there, settings below that will sound like cut unless your room anomalies actually require a true cut of PEQ level. If that's the case usually setting PEQ Gain to 0 or just above and adjusting the PEQ Frequency lower, will suffice.
Phil
