For Win 10:

1. Click the Speaker icon on the right bottom of the desktop and make sure to select the select device (Pimax P2NA). 

 
2. Right-click the Speaker icon and select 7.1 Surround.
 



For Win 11:

Here are some screenshots to show you how to make the settings: 

After you select 7.1 Surround, please click the Next button to finish the settings. Then, wait for about 15 seconds and check the sound.