To set up your surround sound first open up Terminal, or alternatively Alt+F2 and type the following in either:
Now you’re looking for this line, it may be commented out so make sure to remove the ‘;’ in order for it be seen.
default-sample-channels = 2
You might have a different amount of channels set there but simply change it the amount of speakers you have, the sub doesn’t count so 5.1 will be 5, 6.1 = 6, 7.1 = 7 etc..
Ok now you will need to restart you system for these changes to take effect once thats done test them out with this command:
speaker-test -Dplug:surround51 -c6 -l1 -twav