Hi,
I just purchased and set up my sonos arc, currently I don't have my sub and other speakers yet, but Eventually in the coming months I'll have my new TV and sub more speakers etc. I plugged it in with the optical converter it came with for now since I don't have the hdmi arc. I have an appletv not the 4k kind just the regular one and I'm having trouble understanding what selections to choose for all the audio. My selections are tv speakers (hdmi) and arc so I chose arc. On the audio format there's a dolby digital 5.1 or stereo, do I choose stereo because I don't have my rear speakers and sub yet? When I go to watch a movie in hbo it reverts to the speakers labeled tv speakers and I have to manually check “arc” again. What am I missing /not understanding?