I have an Arc, sub and Era 300s for rears. Arc is connected via eArc to an LG G3 TV.
I’m using the Dolby Labs Functional Testing album on Apple Music on an Apple TV 4K. When I play the 7.1 track, everything sounds great. Surround and rear surround channels are very distinct, and the rear surround channels are as loud as the surround channels. Surrounds play from the outside speakers, and rear surrounds from the inside speakers. Great! However, when I play the Atmos tracks, it’s a different story. Surrounds and rear surrounds sound identical, and both come from the outside speakers. It seems as though all I can hear the the inside speaker is probably some reverberation. Is this a bug, by design, or something wrong with my system? The Sonos app correctly shows 7.1 pcm or Dolby Atmos, as appropriate.
As an aside, the Arc was originally connected via Arc to an older Sony TV (so no Atmos support). When I got the LG and connected the Arc to it, I got no height channel playback at all when playing the functional test tracks, even though the app was showing Atmos. I removed the 300s as surrounds and re-added them, and the height channels showed up. I wonder how many people might be blissfully unaware their 300s aren’t working as they should!