New MacBook Pro, year-old cinema display -- no audio!

[jobjobx]

I have a 27" Cinema LED display from last year. It uses displayport, not thunderbolt.

I have a new MacBook Pro with thunderbolt.

I plug in the display's displayport cable to the laptop's thunderbolt output.

In "Properties | Sound" I have "LED Cinema Display" selected, and nothing muted.

PROBLEM: sometimes I get no audio. Spotify plays fine sometimes, youtube videos never. When Spotify audio is absent, I unplug/replug the display a once or twice to get it to work. For some reason, this doesn't work for youtube videos.

???

What to do?

 

[SDAVE]

Hold Option and click the speaker icon in the menu bar, make sure the display is selected.

I know you can do the same from system preferences, but this way you can at least check if it's properly set, quickly.

Could you try another Mac with TB to see if it's not the TB display plug that's the culprit?