Discrete 5.1 surround via Airplay ?


I would like to AirPlay discrete 5.1 from my Mac or iPhone XS to a Sonos Beam.

My Sonos Beam is grouped with two Play: 3s as LS + RS speakers.

When I connect to AirPlay and open Audio MIDI Setup, AirPlay only has the option of 2 outputs, and can't be configured for 5.1 surround. Similarly, everything I stream from my Mac or iPhoneXS is downmixed to stereo.

How do I get discrete 5.1 setup using Airplay ? If it's not possible, how can I get discrete 5.1 surround from my Mac to either a Sonos Beam or Playbar ? My Macbook Pro doesn't support ARC HDMI or Optical Audio Out.

Current setup:

Macbook Pro
OSX 10.14.4
Sonos Beam
Sonos Play: 3 (LS)
Sonos Play: 3 (RS)

Best answer by controlav 18 May 2019, 17:28

Optical inputs on Sonos support PCM (2 channel) or DD (up to 5.1) only.

I don't believe AAC can be physically transported over toslink.
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To the best of my limited knowledge, the only way to get a Dolby Digital signal via AirPlay 2 is to send it to an Apple device, such as an Apple TV. Might be worth more investigation, though, as I'm not 100% sure about that. However, I am pretty sure that an AirPlay 2 signal to a Sonos device is only a stereo signal.

You're trying to do something that the Sonos isn't designed to do, i.e. you're attempting to make Sonos a computer speaker. This makes what you want to do a complex issue. In order to get a 5.1 Dolby Digital signal into a Sonos Beam, you need to either use an optical cable to the Sonos adapter, or with an HDMI-ARC signal being sent back from your TV. So, if you're watching content on your Mac, you need to figure out how to get an optical signal out of the Mac, and connect that to the Beam. It's not designed to take an HDMI signal directly, only an HDMI-ARC signal that is returned from a device designed to send it.

Since your MacBook Pro doesn't support HDMI-ARC or optical, you may be able to use an HDMI-switch to pull off the audio stream. I'm not sure if you can both send an HDMI signal out of your Mac and at the same time have the video on the stream. If so, then pulling the audio out via an optical cable might be possible.
Hi Airgetlam,

Thanks for the quick response.

I bought a Focusrite 18i20 to use its optical audio out:

Audio is routed to 6 ADAT out channels (outs 1-6) in the Focusrite Mix Controller.

My Mac is set to 5.1 surround in the Audio Midi settings, with the first six Focusrite channels as the 5.1 speakers.

The optical out goes from my Focusrite 18i20 directly into a Playbar, paired with two Play: 3s for a 5.1 setup.

The playbar is not detecting audio. Any idea why that might be ? Does Playbar or Beam need some sort of Dolby 5.1 encoding or will detecting 6 discrete channels work for input ?
Sonos can only deal with two specific codecs: PCM/Stereo, and Dolby Digital. So if your Mac, or your other device is sending anything other than Dolby Digital (for instance, DTS), Sonos won't be able to decode it. It definitely won't detect 6 discrete channels.
Hm, I'm trying to isolate the problem.

Using the optical out of my Windows laptop, I can go to Sounds > Playback > Realtek Digital Audio Output (set as Default) > Properties > Supported Formats

In that menu, I can select 'Dolby Digital' and click 'Test' and the 5.1 sound works coming out of discrete speakers. The DTS test does not, like you mentioned.

When I export an .ac3 file from Audacity with silence on the first 4 tracks and audio on channels 5 and 6, audio still comes out of the Playbar.

Can Sonos detect the difference between an Audacity .ac3 file and Dolby proprietary encoding ? For example, is there a header at the beginning of a Dolby file that informs Sonos to decode 5.1 ? Something else I might be missing ?
Ah, just had to enable .ac3 in VLC. Audio's only playing out of the LS + RS speakers now.

On to the next step...
Ok, next question that may be the key to all of this.

Does Sonos Beam accept 5.1 AAC ?
No, I don't believe so. The only formats, to my understanding, are Dolby Digital, and PCM/Stereo.
Note: See the response from Hemanth in this web page:

What I take from that is that the Sonos software will read AC3, but not AAC. Would require a test, which you're much better set up to do than I am, I'm afraid 🙂
Hmmm. I may be wrong. Take a look at this FAQ:

The issue is that this seems to be addressing the music streaming portion, rather than the digital input on the Beam.

And to be honest, you're at the limits of my knowledge, at this point. Perhaps someone more audio codec centric can step in to answer your further questions.
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Optical inputs on Sonos support PCM (2 channel) or DD (up to 5.1) only.

I don't believe AAC can be physically transported over toslink.