This must be the audiophile side coming out of me but back in 2 channel days I ran a single sub running through a AudioControl crossover that had a Linkwitz-Riley filter network (24 db/oct slope, high and low pass, 6 dB down at the x'over freq). I was playing around with my Denon AVR-2805 tonight equipped with Pro Logic IIx music and DTS NEO:6 music and I noticed something disturbing when I was playing with some music. I listen to alot of techno/trance/dance/club style music (lo fi, yes but thats what I like). The system in question is- Polk LSi25 main towers, Klipsch RW-12 subwoofer (with continuously variable phase knob). Anyway, I was using the various modes (excluding the DSP modes, like theater, hall etc) that there was a noticeable difference in the bass response, even when going from "stereo" mode to "direct" mode. So I began to try to pin this down. First I figured since direct was the pure mode it was bypassing the channel delay stuff. I set all the speakers to "zero feet" away from me to eliminate that variable. I also set the front 2 speakers to "0 db" and the sub to "0 dB" on the receiver and adjusted the subwoofer via the subwoofer level incase the direct mode bypassed the internal attenuator. This made things better, at least it was now consistent between direct and stereo mode, although when using the surround music modes there was a different quality of bass. I then began playing with the phase knob on the rear of the Klipsch, I noticed in direct mode, there was most output from the sub at 0 degrees phase and in surround mode, the bass dropped off again and when I reveresed the phase once more it was "OK" again. Da heck, this sux no wonder my bass was never consistent. Is it inherent that dolby pro logic IIx music and the dts:neo6 reverses the phase of the subwoofer channel? Also I have no clue what kind of high pass the Denon employs in the main channels. I think I have a solution to this one. I'm going to run my AudioControl EQ through the main L and R's, set the subwoofer to "none" on the receiver and let the audiocontrol do the bass processing. That way the front 2 speakers and the sub will consistenly be the same, with a much better crossover. Another thing is the Polk LSi25's have built in subs in the towers (although I have them set to small to filter most the bass). Maybe next time around its time to use smaller speakers so I get less intereference but the phase shift phenomena is still there. I wish I could try out another receiver thats compareable to the 2805, see if it does the same thing.