As far as I can see in the code, the XAudio2 (used on windows) output seems to limit to 5.1 audio.
Everything in the AudioMixer seems to take 7.1 into account, and then when it comes down to XAudio it only handles 5.1.
Not sure if you can get around it by using the steam audio/oculus stuff, but I don’t think those handle surround setups either.
I may be wrong about this though, haven’t experimented enough yet.
Is this really the case? Unreal can’t output true 7.1? I’ve been reading around seeing various issues relating to this, and getting reports from users with 7.1 setups that they don’t hear anything at all out of the rear channels as well. It’s a bit concerning.