No Sound over HDMI with 2nd monitor

[Bug-Creator]

O.k. so after my old 2010 imac died I settled for this also 2010 MacMini (2.66GHz, 16GB, 500GB SSD not so bad ) and hooked it up to an 21" FullHD over HDMI.

To my suprise that disabled changing volume inside OSX, but no biggie.

For most part that is the config I'm gonna use but for the rare occasion that I need more space I also hooked up the display-port to the 27" Dell.

All well at start, but after a reboot my system was 100% silent and the 21" only received audio after I pulled the DP cable.

Any way to fix that without the need to constantly change cabling ?

 

[Meister]

Is the hdmi screen the primary screen?

 

[Bug-Creator]

The dock is on the HDMI one and it's the 1st one listed in the sync-options menu, otherwise I see no way of telling which is primary.

After reconnecting it also seems I'm now limited to FullHD on the Dell (no mirroring and the Dell did work at 2560x1440 last time).