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Open the surround sound quicktime in QuickTime Player 10 on the computer

Choose Advanced and then Surround Sound

If you don't see this button

You are not in a surround sound room that will play in 5.1 multi channel

Speaker Input 

Choose Classroom System

Surround Decoder

Projector Input choose

HD-BaseT Classroom System

Keep at Auto and you should be able to mute channels as needed to check the audio.