Thanks for the reply Socketman especially about the room correction software part. I think it would sensible to tweak using the automatic setup recommendations as a baseline.
Update: I have placed by Surround Back Speakers just behind my couch with the primary drivers facing each other parallel at a distance of maybe five feet with the secondary driver more than a foot away facing the side wall....
I did previously place the M3 as a surround side speaker but was unhappy that it outperformed and dominated the other BP6B speakers particularly when running seven channel stereo.
Yes Axiom, I have done my advertising good deed for the day. If only I was a celebrity...
