I wanted to use the sub's high pass filter to filter out low frequencies from the main speakers, but apparently it doesn't have the outputs necessary for this to be possible with my stereo amp. Instead my sub and amp are connected via Neutrik speakon with my main speakers set to "large". They're rated down to 40hz at -6db, and 50hz +-3db. The speaker portholes have been bunged, so I imagine that would probably attenuate the bass somewhat. I'm fiddling with phase and gain by ear, but I'm wondering what a reasonable estimate for the frequency filter on the sub might be? There seems to be a very gradual rolloff on the sub above whatever the frequency is set and it's now set at 60hz. It doesn't sound completely right though, like there's a bit of a gap. Though setting it higher results in what sounds like too much volume in the 80hz area.