It seems to only happen if you have THX Spatial Sound activated, playing or listening to a Surround Sound app or game, and if you have a custom EQ curve.
This completely destroys the audio quality when this happens. After some long talks with support yesterday, I think I've accidentally come across a solution that does not involve sacrificing either your EQ settings or THX Surround Sound.
- Create a blank profile within Synapse and calibrate THX Surround Sound (it's the same as "Spatial Audio", so gonna go with Surround to avoid confusion).
- Turn THX off, making every single source Stereo automatically.
- Now introduce the EQ settings that you may like. In my case, I've found these to be the best EQ settings if you want the flattest-frequency response (from left to right): 4,4,8,0,-6,-3,3,-6,8,8.
- Duplicate the profile.
- Now, on the new profile, you can turn THX back on.
- DO NOT DISABLE THX EVER AGAIN IN THIS NEW PROFILE, OR TOUCH THE EQ SETTINGS. You can still choose which apps will use THX and which ones will be rendered in Stereo from the "Mixer" tab, though.
You will still be able to choose which apps are to be rendered in either Stereo or Surround Sound, just don't toggle the button at the top that says "THX SPATIAL AUDIO" or go into the EQ settings. I don't know if switching back to the original profile may cause trouble, so I'd advice against that once again.
As a last consideration, make sure the quality of the playback and recording devices linked to the Nari are set to the highest possible quality in the Windows' Sounds panel (right click on the audio icon in the Windows Taskbar and go to "Sounds").