I am getting more volume from the Surround L speaker than the Surrond R speaker. Both the speaker are at equal distance from the Listening area. I used Audyssey to setup the Denon 2310 with wharfedale 5.1 speaker package.
If it's the same as AVR1910, just press the CH LEVEL button on remote until Surround L appears on screen, then use left arrow to adjust volume downwards.