How to downmix stereo output to mono on Mac OS X

Let's just open and close this:

Is there a built in way to downmix all stereo output to mono on Mac OS X?

nybergh

Posted 2011-10-20T15:14:40.577

Reputation: 395

Due to my low rep, I won't be able to self answer this until tomorrow. The answer is: http://macosx.com/forums/mac-os-x-system-mac-software/270024-forcing-mono-audio.html#post1514096

– nybergh – 2011-10-20T15:21:07.630

This seems appropriate here, but could also be appropriate over at Audio-Video production. Can an answer be linked without being moved? Mods? – ObscureRobot – 2011-10-20T16:33:38.210

@Obscure Nope, not really possible – slhck – 2011-10-20T18:00:36.553

Answers

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I tried modifying the setting in com.apple.universalaccess.plist, but couldn't get it to take effect:

f=~/Library/Preferences/com.apple.universalaccess
sudo defaults write $f stereoAsMono -bool true
sudo chown $USER $f.plist

An AppleScript that toggles the preference:

tell application "System Preferences"
    activate
    reveal anchor "Hearing" of pane id "com.apple.preference.universalaccess"
end tell
tell application "System Events" to tell process "System Preferences"
    click checkbox 2 of tab group 1 of window 1
end tell
quit application "System Preferences"

Lri

Posted 2011-10-20T15:14:40.577

Reputation: 34 501

Yes, there's an option to enable mono conversion under Universal Access.

System Preferences > Universal Access > Hearing > Play Stereo as Mono.

Stereo to mono downmix under Universal Access options on Max OS X 10.8

Found the answer here.

EDIT 2014-05-25: As explained in Apple's documentation, the stereo to mono downmix option can be found under Accessabilty on Mac OS X 10.9 Mavericks.

System Preferences > Accessibility > Hearing > Audio > Play stereo audio as mono

Stereo to mono downmix option under Accessability settings pane on Mac OS X 10.9 Mavericks

Under iOS 7.1 on the iPhone and iPad, stereo to mono conversion can be enabled here:

Settings > General > Accessibility > Hearing > Mono Audio

nybergh

Posted 2011-10-20T15:14:40.577

Reputation: 395

Ok after a page reload it turns out Lri apparently posted basically the same answer and then some. I'm going to accept his answer. – nybergh – 2011-10-21T00:13:05.137

I edited my answer to include instructions for enabling mono audio on OS X 10.9 Mavericks and iOS. As someone who occasionally has struggled with semi broken headphones and weird PA systems for important presentations, I know I'd be delighted to find instructions for enabling stereo to mono downmixing on all Apple gadgets on the same page. – nybergh – 2014-05-25T14:08:32.627

(Forgive me for digging up an old post...)

On Mac Os X Yosemite (maybe on Mavericks too), the Accessibility window is slightly different and the Applescript posted above doesn't work. Here's the same one with a slight modification:

tell application "System Preferences"
    activate
    reveal anchor "Hearing" of pane id "com.apple.preference.universalaccess"
end tell
tell application "System Events" to tell process "System Preferences"
    click checkbox 2 of window 1
end tell
quit application "System Preferences"

Save it as an app and pop it into your dock for one-click monofying bliss!

Juho Karppinen

Posted 2011-10-20T15:14:40.577

Reputation: 53

Cool. Alternately, I made an app to toggle the setting. It's called "Mono Menulet" http://charlesism.com/monomenulet.html

– Charlesism – 2015-08-04T20:03:00.977