The Equaliser Preferences alter the way REW carries out its EQ filter calculations.
The Default Equaliser specifies the equaliser that will be used for new measurements. The equaliser used for an existing measurement can be changed via the EQ panel.
When matching filter characteristics to resonances the optimiser does not limit filter attenuation, this allows it to correctly determine the required Q for each filter. Once a good match has been achieved, the attenuations are limited to the maximum that the EQ filters allow then the attenuation (but not Q) of each filter is re-optimised accordingly.
If Drop Filters if Gain is Small is selected any Automatic filters which have gain of magnitude less than half the flatness target at the end of the optimisation process will be freed up (their Type will be set to "None")
The default values to use for Speaker Type, Cutoff, Crossover slope, LF Slope and LF Cutoff are specified here, these will be used for each new measurement. The LF Cutoff and LF Slope define the lower extension limit for subwoofer's or full range speakers and how quickly that extension rolls off.
The LF Rise and HF Fall settings define the defaults that will be used for a house curve effect on the target shape for new measurements. The target curve will rise below the LF Rise start frequency at the slope selected until reaching the LF Rise end frequency. A rise at low frequencies is often subjectively preferred. Similarly, the target curve will fall above the HF Fall start frequency at the slope selected. Falling HF response is a normal characteristic of in-room measurements at the listening position.