In order to avoid any issues through the mixer I am plugging the keyboard 1/4" outs directly to the Bose. It makes no difference to the sound whether I use left and right or just left plugs (for mono) and whether I use the Bose phono inputs or the single 1/4" input. The Bose always sounds the same.

If I route the piano through my 5.1 system it sounds like I expect and I have also used a pair of powered monitors and never questioned the sound. I have come to the concusion that I am just not sympathetic to the way the Bose sounds with a piano. It just doesn't seem right to get such a booming bass from my left hand.

However, as I said, some piano patches sound much better.

Tony