Forcing stereo audio to mono on an Apple computer

I recently installed a public address system in a large commercial building and there were two main rooms in which we installed speakers in the ceiling.  These speakers were powered by a rack-mounted stereo power amp in 70V mode.  This was done in order to allow the client to control the volume for each room separately.

Everything seemed fine until the client mentioned that, at times, the overhead music they were playing (originating from their Apple laptop) was…strange.  For some songs, you could only hear the vocals in one of the rooms.  In others, the lead guitar solo couldn’t be heard.

The problem was that the left and right channels of audio were being split between the two rooms.  If the vocals were panned to the right side, you would only hear them in one of the rooms.  I knew the easiest way to solve this would be to send the songs to the stereo power amp in mono.

Fortunately, Apple includes a very simple way to do this to all audio coming out of the laptop:

  • Click the Apple icon at the top-left of the screen
  • Click “System Preferences…”
  • Click the icon labeled “Accessibility”
  • On the right hand side of the window, click the icon labeled “Audio”
  • Check the box labeled “Play stereo as mono”

That’s it!  Now all of your audio will be flattened to mono.  I spent quite some time on this issue, and had a difficult time finding this solution online, so I am sharing it now in hopes that it helps someone else save a little time.

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