This guy is a genius....I have spent hours trying to figure this problem out and how could I or these fools charginig ridiculous amounts of money to tell me it's my problem have ever known where or why this problem is even happening
Long story short I bought a Mac Mini mid 2011 and connected it straight through an hdmi cord to about a 4 year old LG LCD 42" screen with that connected by optical digital to a converter being that my panasonic surround sound only has a analog input. When I first bought my computer everything worked fine the sound passed through the tv, to the converter and onto my surround sound speakers. Last year I purchased a 47" LG Smart TV same setup same everything else and my sound would pass through the hdmi cord and not all the way to the surround sound, which after spending an hour on the phone with Apple only to get an answer of "I think you should buy a new surround sound....well dip my call could have paid for it....anyways tried so many different options messing with settings so on so forth only to find nothing that worked, until my roommate hooked up his late 2012 mac mini to find the sound passed through once again just fine. So here's what I did downloaded the mountain lion operating system went into garage band changed the audio output under preferences and POW back to normal...thanks dude
I had a silimar issue with getting audio out of my mac mini via hdmi.
Followed this and fixed it:
Hope someone finds it helpful.