How to setup the surround speakers (5.1 and others) with ALSA

• Edit the ~/.asoundrc file, create it if it doesn't exist:

gedit ~/.asoundrc

• Enter the following section:

pcm.!default {
   type plug
   slave.pcm "surround51"
   slave.channels 6
   route_policy duplicate
}

• This will allow to play the surround output and duplicate the stereo output to all 6 channels (not only front ones).