I don't know if this has been fixed, but Counter-Strike: Source only shows "2 Speakers" as well, even though I also have headphones plugged in (USB Headset).
It still only shows 2 speaker configuration. The Windows version had a profile for headphones.
This is not only an issue for Source engine based games - GoldSrc games output stereo-only too.
However, it seems HL and CS feed some 5.1 audio stream to pulseaudio, but the actual sound is played via a separate stereo stream.
As far as I can see, SDL is currently used as the audio backend for all these games.
OpenAL support would be nice.
Issue transferred to ValveSoftware/Source-1-Games#93.
This issue is closed - continue conversation there.
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I have 5.1 audio and "Analog Surround 5.1 Output" profile is selected in PulseAudio.
![2013-01-31_00001]()
But Audio options offers only "2 speakers" and by default nothing is selected.
System info: https://gist.github.com/4634761