Set up audio devices on iMac (Mid 2011) and later
How do I Set up audio devices on iMac (Mid 2011) and later
iMac, Mac OS X (10.7.5)
How do I Set up audio devices on iMac (Mid 2011) and later
iMac, Mac OS X (10.7.5)
I don't suppose you read this: Set up audio devices on iMac (Mid 2014) and later?
Please read Writing an effective Apple Support Communities question.
What type of audio devices?
Set up audio devices on iMac (Mid 2011) and later