You can GROUP one Play:1 with your Arc in the Sonos app, but you will experience a slight delay from the Play:1 when playing TV audio. Streaming music will be in sync.

If you want the Play:1 to act as a true surround speaker for the Arc, you need to use TWO Play:1s.

To fix the cutouts, try unplugging the Play:1 from power for a couple of minutes and reboot your router.

That's not surround sound.  That's 2 speakers playing the exact same content.  Surround sound is 5 discrete channels + 2 height channels and a Sub in specific locations in the room, giving you 3D sound, complete with spatial and directional cues.

Next time it happens submit a diagnostic to Sonos ASAP and call them (with the number) when you can, they will be able to look into what caused the drop.

Do not wave the red flag of “surround sound” at the tech, if you do they will likely get diverted down that rabbit-hole and away from solving your Grouping problem.

Thanks for the replies. I wasn’t even intending surround sound when I put the Play 1 in the living area 2 years ago. Maybe it’s the very slight delay I like, but it sounds better to me than just the Arc speaker. So I never set up surround sound. But I don’t understand why it worked fine for 2 years and now I’m getting breaks in the sound where the Play 1 cuts out.  I tried unplugging everything and rebooting everything and it doesn’t fix the problem. I also did the support and submitted a diagnostic, not mentioning surround sound, but the tech kept insisting that I need 2 Play 1’s. Again, it worked fine for 2 years. 

It’s not that uncommon for wireless interference to be introduced in a location whether previously was none.    A neighbor could have gotten a new router, or even your own router automatically switched the wireless channel it was using, causing interference with the sonosnet your speakers are using (assuming on of your speakers is wired to the network).

One quick an easy thing you can try is changing the sonosnet channel.

Networks can change. There are no networks, either WiFi or SonosNet that exist in a ‘vacuum’. They can always be affected by not only internal things, such as updates to the router’s firmware, or IP issues due to an Sonos update process clashing with the router’s DHCP table, but also outside influences, such as other WiFi devices in the environment, or even simple electrical devices leaking into the spectrum used. Or, other external influences, such as a neighbor setting up a new signal that stomps on yours, or even unusual sunspot activity sending radio bursts of energy that temporarily flood the radio spectrum. 
 

All of these issues can change any network’s ability to carry data, even though it has previously been stable. It’s why all of the folks here are recommending the things they are. They’re aware that a network is not an immutable object, but much more of an elastic and constantly changing thing. 

Thanks again for the responses. Since my last post, I rebooted everything again. Still no change. Then I installed a wifi Extender. Still no change. I downloaded the AT&T app. From this app, I can walk around with my phone and check the wifi signal. It is strong all over my house. This morning, I tried using an ethernet cable directly from my router to the Play 1. The sound cutting out still happens. So, unless there is something wrong with my TV, with my limited tech brain, I’m thinking the speaker just developed an issue. 

Then I’d certainly recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. If there is a failure in the speaker, it’s likely to show up in that. 

If not, there may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.