...What is HPQ??...
Its a high pass (HP) filter where also the Q parameter is adjustable, for example picking textbook filters in software as Butterworth and Linkwitz Riley the Q parameter is a frozen value dictated by the filters name and its slope order, so for example a 2nd order Butterworth filter Q is 0,7071 and for 2nd order Linkwitz Riley filter Q is 0,5, one can adjust filter frequency but not the Q parameter, below graphs show example of two named texbook filters and the relative high Q=1,17 filter that is asked for here @41,7Hz..