I have two monitors connected via DisplayPort cable to the same graphics card, though I've disabled their audio in Windows sound manager. I installed an Nvidia 1080 graphics card in Nov 2017, which is what the audio receiver connects to, but I'm confident the system has worked correctly since then.
#Via hd audio drivers windows 10 5.1 surround how to
I'm not sure how to trace this to a root cause as I'm not sure how long ago the setup stopped working correctly. If I go into the menu within the audio receiver, I am able to play test tones confirming that the receiver itself can send test tones to the proper speakers, which makes me confident this is coming from Windows and not my hardware setup. If I switch the Speaker Setup in Windows to just stereo, the stereo audio correctly plays with left audio coming out of front and rear left, etc. The test tone for the bass plays normally.
I've gone through the Windows 10 speaker setup menu to confirm that they're still set for 5.1 Surround, but when I hit 'Test', the tones for all 5 channels individually play through the front speakers (Left, Right, Center), and no audio ever comes out of the rear speakers (though the tones intended from them do play through the three front speakers).
Today I tried to listen to an album mixed for surround and realized my setup was no longer channeling audio correctly.
I have had an Onkyo 5.1 audio receiver hooked up to my PC for years via HDMI with no past issues getting 5.1 audio to properly output.