FordPrefect,

Yes, you are correct. Because of the way our external pinnae are shaped (that's the outer ear, and no smart remarks!) and focused, and the psycho-acoustics of hearing, if you are going to add extra channels on the rear wall, it's preferable to use two, and space them apart, rather than a single speaker.

In short, do 5.1 or 7.1.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)