By default pulse audio in Ubuntu is configured to use only 2 speakers. For someone like me who wants to get the most performance possible out of their surround sound system this is simply unacceptable. Luckily adjusting this only involves one quick edit.
To enable more than two speakers (known as channels) we need to make an edit to the pulse audio daemon configuration file. This will require root privileges, which we will gain using the gksudo command. Press Alt+F2 and run the following command:
gksu gedit /etc/pulse/daemon.conf
You will be prompted for your administrative password, then the configuration file will be opened in Gedit (note that if you are running KDE instead of Gnome or Unity replace gedit with kate). Search for the following line:
; default-sample-channels = 2
We want to un-comment the line by deleting the semi-colon and change the channels from 2 to 6. The final result should look like this:
default-sample-channels = 6
Now reboot your system. Your sound should now be configured to output to 5.1 surround sound. As always if you have any issues please feel free to comment below and we will be more than happy to help you out!
Image from Deviant Art.