Why is my surround sound device not properly recognized by Source?
Source games rely on the operating system to identify the audio device for them. If your surround setup is not properly configured in Windows or is configured through a proprietary control panel, it may not be properly recognized by Source games.
Ensure that your audio device is setup appropriately in your Windows Control Panel.
Launch the game and adjust your settings in the Options > Audio menu.
If the issue persists, close any proprietary audio control applications and repeat the process.
You can also use one of the following launch options to test the issue: