I searched the topics and didn't see anything similar to my issue. I apologize if it's been discussed and I didn't see it.
Set-up a new 700 Soundbar with Subwoofer this evening. Running all my video channels through an Onkyo receiver and have the soundbar set up through the tv using the HDMI Arc.
After playing with some settings on the tv and the receiver started to get sound through the system. The movies played through my cable box ( HBO) etc..all sound great. You can hear the effects and the converation. When I stream movies through AppleTv ( Netflix / History Channel) it works as well as it does with the cable.
When I go to play a movie purchased in itunes, the movie score, effects, and base all sound good but you cannot hear the conversation within the movie. It's as if the center channel doesn't exist.
It sounds like it may be the particular audio format from the iTunes purchases. Can we check the audio output settings of the Apple TV and see if we can set it to Dolby Digital instead of automatic. My thought is that since the Apple TV is connected to the Onkyo receiver which can handle more formats than the soundbar, it's causing playback errors.