I believe if you have 7.1 source material they should be descrete channels and not mono. If you have 6.1 material it will be the same signal (mono) for both rear channels.
Some processors like Meridian will create their own side channel signal from 5.1 source material when you have a 7 channel system.
Check your processor manual to see what kind of capability it has.
Some processors like Meridian will create their own side channel signal from 5.1 source material when you have a 7 channel system.
Check your processor manual to see what kind of capability it has.