Why can't I adjust the individual speakers here/why are the sliders greyed out?
I setup a surround sound system on my iMac through the Creative Sound Blaster Omni Surround 5.1. I found that the rear speakers seemed quiet so I went to the Audio MIDI Setup to adjust the volume of the rear speakers and found the sliders greyed out (as pictured). Can someone tell me how to change it so I can adjust the sliders for the individual speakers?
iMac (27-inch Mid 2010), OS X Mavericks (10.9)