How to disable headset enhancements in Windows 7/8/10
Some headphones contain stereo splitting circuits that will effectively prevent bilateral sounds from being generated. A stereo splitter circuit forces sound to both ear pieces and changes the volume levels between the two sides. As a result bilateral sounds will be heard in both ears. Also, some sound cards activate a "Stereo Virtualisation" filter when they detect that headphones are plugged in. This filter has the same effect as a stereo splitter circuit.
If affected you should use a different type of headset and or disable "Stereo Virtualisation" and "Virtual Surround" options (see below):
Open Audio Devices and Sound Themes by clicking the Start button, clicking Control Panel, clicking Hardware and Sound, and then clicking Sound
Select "headphones" then click on "properties" (whichever result in the Enhancements tab being displayed on your system)
Click the Enhancements tab, and then ensure that Headphone Virtualization and Virtual Surround are unchecked and or check "Disable all enhancements" if the option is presented
Click on "Apply" then "OK" to exit
Additionally on some systems with some headsets it may not be possible to bilaterally pan mono files using the background sound player. Mono files should be converted to stereo files or the large media player should be used instead.