What connection are you using for the Arc Ultra to the Projector? What is the distance between them? What are the audio sources you’re playing and what audio codecs have you tried? Are any Sonos products wired to the LAN - are you using a 2.4Ghz or 5Ghz WiFi connection - what channels are in use on the router. Have you tried a different cable for the connection between the projector and Arc Ultra?

Hi Ken, thanks for your detailed response. I am using an HDMI cable that I purchased separately. I have not tried a different cable between the projector and the Arc Ultra. The cable is 10 meters long. The projector is ceiling mounted in front of the screen, about 2.5 meters away. The HDMI cord doesn’t go straight to the screen and down, but rather to the left and then makes its way across. It’s more hidden that way. The projector itself has Chromecast and other apps built in, such as Netflix, YouTube, and Spotify that I all use to play sound. It has the same effect whether it’s sourced from a music or a movie. I have the two Era 100 speakers mounted on the wall across from the projector screen, up above and in the corners of the wall behind the couch. Those are super quiet but they do work. None of this is wired to the router. All of the speakers are connected via WiFi on the SONOS app. My main WiFi network has both 2.4 and 5 GHz but I can’t find any specifics on which is used. Thanks for your help!

I personally suspect the HDMI cable as possibly being the issue here  - just as a quick test, are you able to easily swap-out the HDMI cable and use the one that came with the Arc Ultra, just to see if the audio interruptions go away? - Try playing a movie on Netflix - something like ‘6 Underground’ and check the ‘Now Playing’ Screen in the Sonos App to ensure you’re getting surround sound for the TV/Projector audio. 

For Music audio, (Sonos Radio etc.) via the Sonos App, switch the rear speakers from ‘Ambient’ to ‘Full’ in the ‘Surround Audio’ section of the Arc Ultra ‘room’ settings and see if you get the audio output you’re perhaps looking for from the rear surrounds.

I did not notice that there was an HDMI cable that came with the Arc Ultra. I will have to buy another one but it’s worth a shot to try that. 
 

I also already had the surrounds on “full” rather than “ambient”. It seems like the right surround is quieter than the left. I can really barely hear it. 

I would try another cable - any short cable will do as a temporary test if you’re able to move things closer together, just to see if it improves things. Have you balanced the HT speakers using TruePlay tuning with an iOS controller device? If not then try that, or if you have, try toggling off TruePlay in the room settings to see how that sounds.

Hey Nat.e! For 10 meters and longer you should use fiber optic hdmi cable. Is your cable fiber optic?

I got a new HDMI cable and it’s not popping or cutting out anymore, and the surrounds sound better too! Thanks for the help :)

Hello! I use my Arc Ultra connected to my eARC BenQ TK710 dolby atmos capable projector. I use an ATV4K 2022 edition. Very often whenever I want to stream Atmos content on any platform I get no audio at all! The Sonos app shows no audio! If I force the ATV4K to play DD5.1 then it works again! Or If I leave it on Auto, Atmos on then the 5.1 content reads Stereo PCM on the Sonos app. Is this happening to you? I have changed cables..I am using Ruipro 8K fiber optic cables 25 ft the green ones and still the same issue. I have to disconnect the Arc from power and plug it back in for it to work again with Atmos.

So you’ve said here: