Yesterday, I looked at my subwoofer setting again and here's what I have. BTW, this is Velodyne CHT-10 (powered).

It is connected from the pre-out subwoofer output of the receiver to the sub line-level inputs. And the switch is toggled to Direct as opposed to Internal X-over. Low pass crossover dial is at 80 Hz (I don't know if it's relevant because it was set to Direct, and the receiver crossover is already set at 80Hz).

As for my front speakers BW 602, the frequency range is from 49Hz to 22Khz., the rear BW 601 from 60Hz to 22Khz.

Is this the optimal configuration ? Any suggestions are most welcome.