preQursor2 features uniquely designed filters with low resonance peaks 01/06/17
PSP says that preQursor2 offers PSP's uniquely designed filters with low resonance peaks for reduced ringing artefacts, great band separation, and narrow notching when attenuating. They tell us that all four filters are bell-type filters when boosting, and have progressive Q factors.
Here's the rest of the story in their own words...
The PSP preQursor2 introduces PSP's Advanced Analog Modelling of preamplifier and filters to accurately recreate an analog-like behavior. The analog modelling algorithm can be enabled and controlled per instance, or globally per group of instances. The latter allows for easy control of the amount of analog- like processing on either selected tracks or all tracks in the mix. All these characteristics result in a processor that not only sounds excellent on acoustic tracks, overall mixes, or any other application, but also allows you to virtually create the input console for all tracks in your mix with easy and convenient controls. In every usage case, PSP preQursor2 will maintain the natural feel and definition of the material.