Is the M 7.1 "direct"? (cause I assume you mean MCH 7.1. Onkyo gives you a choice of direct MCH or "bass managed" MCH)
If it is, it is bypassing your bass management. DPL would use the bass management no matter what. Your bass management could be splitting the bass up to the 7.0 in DPL.
But, for us to know that...we'd need to know your crossovers in the AVR itself.
I've got my crossovers set at 80 and speakers set to small, with everything calibrated via Auddesey MultiEQ. I don't think it has anything to do with my crossovers.
When outputting from XBMC I use WASAPI for bitperfect audio, which I'm sure you know bypasses any decoding on the part of xbmc, in favour of sending the stream untouched to the AVR, where upon the AVR uses ( when I've got it selected ) Dolby pliiX to decode and output the signal. If however I select " output to all speakers " in xbmc, the avr reads as Multi Channel in 7.1 - which is what it incidentally reads when playing signals that are already decoded and sent to the AVR. For instance any music program that doesn't use WASAPI will just decode the audio itself and send it to the avr to output, as opposed to the AVR decoding ( my preference ) the signal itself and outputting it as Dolby plii, ( or neo 6 or whatever else I choose ) ... I can only surmise that by somehow selecting output stereo to all channels in xbmc, it's processing the music before it leaves the PC, and for some reason adding heavy bass to it.
Direct is a different setting on the Denon, I don't use it, as that bypasses the settings I've got in Auddessey, speaker distances, crossovers, everything.
It's a confusing setting on the AVR, the " multi in 7.1 " - as even if I've got XBMC set to output to all channels, and it displays M in 7.1 ( as opposed to PLiix with the option off in XBMC ) I can still select " Multi channel stereo " on the AVR, and have it output to all speakers, ( which it was already doing, with M in 7.1 ) but in a different way.
In any case I still can't figure out why Multi in 7.1 ( that is displayed when XBMC is set to output to all speakers ) is so much louder with respect to bass. Maybe xbmc is mixing the two channel FLAC files INTO 7.1 channels, then sending it, as opposed to " multi channel stereo ", which is just a stereo signal split evenly between all the speakers.
Edited by sean1976, June 16 2013 - 05:41 PM.