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I would like to output all system audio as mono in OSX.

Following this answer, I tried checking the "Play stereo audio as mono" option under the System Preferences > Accessibility tab, but it has no effect.

I have a 13-inch late 2008 Aluminum Macbook that I have upgraded to El Capitan 10.11.2. This Macbook model would have come bundled with Leopard, but apparently the mono audio feature was added in Snow Leopard.

So I suspect the problem might be that my old audio device doesn't support mono output, but post-Leopard OSX has an accessibility option because it is designed for newer machines that do support mono audio.

Can anyone confirm if this is true? If so, is there any other way to produce mono audio output on this old Macbook?

Community
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willpett
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  • Yosemite has the same Accessibility option to play stereo as mono. What OS version did you upgrade from, and did it previously work? –  Feb 12 '16 at 17:07
  • When I got the machine it had Yosemite installed, but I never tested the mono audio feature until I upgraded. So I can't confirm whether it worked previously or not. – willpett Feb 12 '16 at 18:55
  • So what are your symptoms, how do you know 'it has no effect'? (wondering whether you have a problem with your headphone jack). Works on my late 2008 with Yosemite. –  Feb 12 '16 at 18:58
  • I created a test audio file with a constant tone in the left channel, and clicks in the right channel. After enabling the mono accessibility feature, I can still hear the tone only in my left ear, and the clicks only in my right ear. (specifically, I replicated the stereo/mono test from [this post](https://discussions.apple.com/message/18064210#18064210). My results for step 7 are the same as for step 5, indicating "no effect"). – willpett Feb 12 '16 at 19:06
  • I downloaded Audacity, generated a left track of silence, a right track of clicks and listened. Left silent, right chirps. Ticked => ***Play Stereoaudio as mono***, and got chirps both channels. (Used Sony MDR-V6 headsets, Late 2008 Aluminum Macbook, Yosemite 10.10.5). Not hardware specific (other than headphones - jack?) –  Feb 12 '16 at 19:35
  • Interesting. I tried three different pairs of headphones and nothing happens when I check "Play stereo audio as mono". Audio is normal otherwise, there is no obvious distortion or weirdness that might indicate a faulty jack. Plus, I assume the audio is mixed to mono before it arrives at the audio jack, so audio would still be mono even if the jack was messed up. – willpett Feb 12 '16 at 20:42

2 Answers2

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Try to go to the Universal Access or "Accessibility" system preferences. In the audio section you will have an option to play stereo audio as mono. You need to check this box, and your audio will be played as mono.

Tim Stuart
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Was having this same problem and got it to work by checking the box on, then restarting my computer and reconnecting to the bluetooth speaker I was using.

Hopefully you've figured this out in the last 3 years but maybe it'll help somebody in the future.

Adam
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