How does one properly set Q for "X"-pass filters ("X" being either high or low)? I understand that for band-pass filters, F_center = SQR [ F_min * F_max ], i.e., the square root of the product of the -3dB cutoff thresholds for the specified bandwidth. Q, then, is F_center / [ F_max - F_min ], where the denominator is the bandwidth of the filter. It is my understanding that the "X"-pass filters are of second order type, i.e., implying -12dB/octave attenuation. So what does Q do with respect to "X"-pass filters? What would be the most effective means to eliminate any signal <50Hz? On the one hand, the 4th order cross-over suggests and inherent -24dB/octave attenuation at the crossover point, but uses significantly more resources than a notch filter. While the notch filter uses as much resource as a high-pass filter, and I'm clear on how to configure Q for a notch filter, I'm unsure whether implementing a high-pass filter instead wouldn't be more appropriate. Perhaps its 6 of one, and 1/2 dozen of either the other two? Right now I'm running a notch filter with F_center at 20 Hz, and Q = 0.5 so that should get the job done. FWIW, the whole cause of my consterntion was noticing distortion in the sub-woofer when the EQ 10-band 32Hz slider had a bit too much gain. Digging deep into the rules I discovered the freq. response for my Monsoon MM-700 speaker system runs 50Hz - 20kHz. Drilling deep into the rules for the CT4780 soundcard suggests that the 10k1 DSP has a freq. response between 20Hz - 20kHz. There's an equation that describes power with respect to frequency, not putting the energy the woofer can't handle into the active 3rd-order cross-over would be conducive to minimizing unecessary stress on said components and retain fidelity when taching the system to the red-line (if you know what I mean).