Why does Windows 10 send mono audio to the center channel of a 5.1 setup?

Question

When playing mono audio (eg an old video on YouTube) Windows 10's behaviour is to send that to the center channel.

Is there a way to get monaural audio streams to play through the front L/R speakers as dual mono without going into audio properties and disabling the center channel?

Answer 1

Standard policy of all Windows versions that support multi-channel output is to map a mono stream to front left/right channels of multi-speaker system. This is exactly what you need.

The problem may be in wrong speaker/channel configuration. Since a single-speaker (mono) configuration consists only of the center channel, default channel distribution mask for a mono stream is KSAUDIO_SPEAKER_MONO, that corresponds to SPEAKER_FRONT_CENTER. So if the application uses extended audio format specification (WAVEFORMATEXTENSIBLE) on audio endpoint access, and specifies KSAUDIO_SPEAKER_MONO for mono streams, the sound will be directed to the center channel only.

But most applications don't specify explicit channel distribution masks explicitly for mono and stereo sounds. In such cases, Windows uses default mapping rules, and mono sounds are directed to both front left and right speakers.

If you are sure that all settings in both Windows audio properties and audio adapter's own control application (if any) are correct, you need to try some different audio playback applications to isolate the problem.