Hi @ustad2be
No problem.
Grouping to play TV audio in other rooms can work, but it’s not officially supported. When synchronising music playback, the music can be pre-buffered and frames of it can be arranged to play at certain exact times - this is what Sonos is about. When playing TV audio, however, the main Home Theatre device (Arc, in your case) is unwilling to wait for buffering so that it can stay in sync with the picture on the TV. Surrounds and Subs are on a direct 5GHz link and can play without delay. When playing TV audio to other rooms, the network is involved which has a slower connection (Arc connects to the router over 2.4GHz) and extra devices (the router itself, and any other network devices on the path to the destination). Therefore, TV audio can played over the network, but it’s either going to suffer dropouts due to lack of buffering, or be delayed and therefore out of sync with the HT room if the buffer is increased.
You can increase the size of the buffer by going to Settings » System » [room with Arc] » Group Audio Delay » Medium/High/Max. Experiment, and choose the lowest value that results in no dropouts. If you can’t hear the Arc in the other rooms, it should be acceptable. If you can hear the Arc, you may not find the result tolerable.
If you have the option of connecting the Arc to ethernet, that may also improve matters.
I hope this helps.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein