[BUG] The game seems doesn't recognize virtual 7.1

I'm using Sound BlasterX G1.
Xonotic can't recognize my sound device as 7.1, but stereo. Typing 'soundinfo' in console returns it has 2 speakers. I tried to set the channel to 7.1, nothing works but set back to stereo automatically.
Maybe OpenAL doesn't support Sound BlasterX? Any ideas?

The game is based on a derivate of the quake2 engine(quite old) so I doubt it's directly supported (maybe stereo is even the max supported channels). And theres probably noone seeing it as prioriy who could actually fix it.

According to every source i can find, Darkplaces is based on a Quake 1 engine, not Quake 2.