The way to test whether the headphones work properly would be to do this: 

- Set your soundcard to Stereo Only (2 Channel). 

- Load up a stereo file or CD track in Windows Media Player (or the player 
  of your choice). Do not use any surround-encoding or 'expansion' processes
  on the audio. Just plain old stereo. 

- Plug the GREEN plug from the headphones into the GREEN jack on your
  soundcard. Check that the Left and Right channels are playing properly. 

- Now unplug the GREEN plug and plug the BLACK plug into the GREEN jack 
  on the soundcard. Listen, and check that the Left and Right channels 
  are playing properly. 

- Unplug the BLACK plug and plug the ORANGE plug into the GREEN jack on the
  soundcard. You are only listening to make sure that the Center and Subwoofer
  drivers are working, so don't worry about Left and Right (they won't be
  playing correctly). Just make sure that you get both high and low sounds 
  (Center and Sub, respectively). 

If all that worked as expected, then the headphones are OK.
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