Thanks - I think what's happening is what's described on this Focal page (not the manufacturer of my speakers but probably the same situation) - Problem of speakers considered as out of phase during automatic calibration | Focal - it's due to a phase reversal due to crossover design that YPAO is misinterpreting. However instead of just ignoring the warning they recommend switching polarity temporarily during calibration and then putting it back to normal afterwards. This isn't advice I've seen elsewhere but it does seem to work for me so hopefully this helps others who run into this issue :)\n\nThe only phase issue I've ran into was a amp I had Emotive XPA-5 one channel was out of phase. I discovered that after running ARC with a Yamaha 7790.\n\nAbout drove me nuts trying to find that phase issue. After checking every speaker wire connection and I mean every driver.\n\nLast resort was pulling all interconnects. Re wiring back to just the Yamaha 7790, and Walla no more phase issue. The center channel on that Emotive XPA-5 was wired wrong at the input. I ordered a new board from Emotiva replace it myself. I gotta say that XPA-5 was worth it's asking price new from Emotiva.