Question: Set/Reset HDMI audio output
Just wanted to share!: I was scr*wing around with all the mentioned settings I could find, based on all the stories about this problem you can find on the internet. For years now, only my left speaker worked. I had already concluded my speaker was probably damaged (hardware defect) Yesterday though, I connected my macbook to the TV via HDMI and I set the audio OUT device to HDMI. I wanted to hear the sound on my TV. Later I disconnected the macbook pro and today, suddenly my right speaker appears to be working again!!! For some reason, at some point, something went wrong with a software setting I guess. It might have some to do with plugging/unplugging headphones aswel. Try to do this HDMI audio OUT and unplug again, if you can't get any further on this.
This fixed my problem with only the left speaker working on Macbook Pro late 2013
MacBook Pro with Retina display