Hi @ramshazar
So the only solution for this problem could be to force the Apple TV to output stereo instead of multi channel PCM in order to receive the stereo up mix from the beam, right?
I think that would be the only solution for your current headphone connection method, yes. However, I do not work for Apple and have never owned any of their devices - it’s possible I am missing something.
Unfortunately, my LG OLED isn’t capable of playing line-out or toslink optical out with HDMI simultaneously. A lot of TV manufacturers don’t do this. I think only Sony and Panasonic have a few TV models that can output audio through line out and TV speakers or HDMI simultaneously. We really have to look for this option when buying a new TV. But for now (and the next years)… too bad. :(
Well, if the TV won’t do it, a HDMI audio extractor with a 3.5mm stereo jack (if that’s what the headphones use) output should. This would only work with external sources (so not with the TV’s apps), but it sounds like you mostly use your ATV anyway. Such a device will not be expensive, though I recommend ensuring you have the option to return it if it doesn’t help. They range from about £$€15 to 50 - personally, I would aim somewhere in the middle, but try to ensure it will decode the audio formats you use, like Atmos. While I can’t recommend a particular unit, a search of “HDMI audio extractor 3.5mm atmos” should yield plenty of results. This device would sit on HDMI between the TV and the ATV (not between the TV and Sonos).
Please remember that such devices are unsupported by Sonos, and that it is a personal opinion of mine that this all should work - Sonos cannot take responsibility if it does not.
I hope this helps.