Depends on what Sonos devices you have. There would be two methods that could be used, either a line in on the appropriate Sonos from your headphone output on the Mac, or AirPlay 2 to a Sonos device that is AirPlay 2 capable. 

Bruce, thanks for your reply … I have 2 One (Gen1) speakers, a Connect with attached pre-amp, and a Playbase (through which smart TV plays). Am hoping to connect wirelessly to Sonos (wifi?). WRT AirPlay2 capable Sonos speakers, I don’t think the One (Gen1) versions are capable? - perhaps you can confirm. If so I guess I am out of luck. :(

David

Do you have two Sonos Ones, or two Sonos PLAY:1s?

The PLAY:1s are not AirPlay 2 capable, but Sonos Ones would be. 

Oh, and are these Ones/1s set up as surround speakers?

Speakers are Sonos Ones, and have (now) figured how I can use AirPlay to output laptop audio - thanks for the Airplay reminder. No, I have not set the speakers up as surround speakers as all are in separate rooms.  One final question (and maybe should go to Apple forum) is it possible to play simultaneously to multiple AirPlay speakers at the same time from Mac laptop using OSX 10.15.5 Catalina?

Many thanks again!

David

As far as I know only iTunes, within macOS, can output to more than one airplay device simultaneously (odd to leave it out of the audio panel when it’s there in iOS)

But two other options:

1. group the other speakers with the one receiving AirPlay audio, using the Sonos app
2. RogueAmoeba’s Airfoil can redirect any app’s audio to one or more AirPlay devices and keep them in sync.

I *think* it is, but I think maintaining separate AirPlay 2 streams can be troubling for a sending device, I’d recommend just grouping the Sonos with a single AirPlay 2 stream going to it, and rely on the Sonos software to keep everything in sync. I don’t think two or more AirPlay 2 streams are designed to sync up, as they would depend on the processor speed of each receiving device to decode the signal. I think. 

Did I say I think enough times? :)

Appears we have a solution. Started up Hearts of Space on the laptop and once audio playing via computer, selected one of the Sonos One Airplay speakers - working fine. Then went to Sonos app and grouped all Sonos speakers together and now computer audio stream playing over all Sonos speakers - awesome sound! Control volume from laptop via System Preferences - Sound.

Thanks to both of you Airgetlam and jrguk, great insight and suggestions.

David

Just a small postscript, output to multiple devices in synchronisation is an advertised feature of Airplay 2.

”With AirPlay 2, you’re in control of your audio. And if you have more than one HomePod or AirPlay 2–enabled speaker, you can enjoy your favorite music or podcasts throughout your house — in perfect sync.”

https://www.apple.com/airplay/

(But, as I said, on macOS only iTunes natively supports it.)

I’ve never tried it, but I’ve certainly seen complaints about Apple not doing well with sync. I tend to use a single AirPlay stream, and let the Sonos handle the sync aspect. 

Interesting comments, Airgetlm and irguk. Only limitation I experience with the current setup is that once have established audio link between laptop and  a single Sonos One speaker as detailed in previous post, while I can see my other speakers in the Sound panel under Airdrop, there is no way I can figure to send the stream to these other speakers, simultaneously. Instead I find I can do this going through the Sonos app and arranging the speaker grouping as I wish.

Need to look closer at whether I can use AirPlay 2 to connect directly with my Sonos One speakers as alternative method. Thanks again!

While I never do it, you should be able to just click on the selector next to each speaker, and create a new AirPlay 2 stream from the Mac to the new speaker. Doubling the bandwidth exiting the Mac, of course. 

Oh, if you can’t do the selecting as I indicated, that’s an issue on the Apple side, Sonos only presents “I’m a speaker” to the OS, the OS handles everything from there.