So I recently installed Ubuntu on my second HDD in anticipation for Steam on Linux, but came across a problem concerning 5.1 surround where my subwoofer wouldn't work properly. If I tried to play an MP3 file, I'd get no bass whatsoever. Pausing the song and clicking on the "Analogue Surround 5.1 Output" option in my sound settings fixed the problem temporarily, but as soon as another song started playing, I'd get no bass again. After doing a bit of research, I was able to discover the following fix...
Firstly, make sure your sound settings are correctly configured. Set the mode to Analogue Surround 5.1 Output as mentioned earlier. It should look like this...
Next, you'll want to open a terminal and enter the following;
gksu gedit /etc/pulse/daemon.conf
Scroll down until you find the following line...
; enable-lfe-remixing = no
... and change it to this, making sure you don't forget to uncomment the line;
enable-lfe-remixing = yes
Save the file, return to your terminal and enter the following command;
Once the command has executed, try playing some audio. You should find that your subwoofer is working once again!