There are a bunch of threads on this already. Here’s the main one with the right settings. https://en.community.sonos.com/home-theater-228993/lpcm-eta-for-arc-6842558/index4.html
Basically you can get Atmos/DD 2.0 or DD5.1 and no Atmos depending on the settings you choose. Meaning you have to manually switch between having Atmos and having DD 5.1. It’s because of an LG firmware update and Sonos’s not yet supporting LPCM. Sonos has announced support for LPCM in the future. Right now, the solution is to use the LG built in apps or you can manually change your settings when you use the Apple TV.
I’m not sure what is causing you to hear no voices, but try the settings shown in that thread.
Thanks ewolkoff
I searched with no luck. That is a good thread. To save folks a dig and add a few more takeaways / basic comments:
Sonos update needed and “in development” as of 8/2/2020 to allow AppleTV4K to work in . So in meantime no Dolby Atmos (big deal as THAT is the feature to allow home theater sounds from Sonos arc to appear to come from ceiling… why you paid the big bucks to get… otherwise just get a regular soundbar and save a lot of money)
In meantime - just to hear voices in AppleTV4K (Forget the Dolby Atmos dream… just trying to get arc to work as a normal speaker) - must go to settings in AppleTV4K and force Dolby 5.1. To do this:
Settings → Video and Audio → Audio Format
Change Format → On
From there you can set to Dolby Digital 5.1.
Thanks ewolkoff
I searched with no luck. That is a good thread. To save folks a dig and add a few more takeaways / basic comments:
Sonos update needed and “in development” as of 8/2/2020 to allow AppleTV4K to work in . So in meantime no Dolby Atmos (big deal as THAT is the feature to allow home theater sounds from Sonos arc to appear to come from ceiling… why you paid the big bucks to get… otherwise just get a regular soundbar and save a lot of money)
In meantime - just to hear voices in AppleTV4K (Forget the Dolby Atmos dream… just trying to get arc to work as a normal speaker) - must go to settings in AppleTV4K and force Dolby 5.1. To do this:
Settings → Video and Audio → Audio Format
Change Format → On
From there you can set to Dolby Digital 5.1.
This information is wrong. When set correctly AppleTV outputs Atmos to the Arc via an LG 9 series OLED. But if you set it that way, you have to change the config back to get Dolby 5.1. Please read the other thread and see the screenshots with the AppleTV 4K outputting Atmos.
I disagree and must be missing your point.
I got that information from the other thread.
It worked.
You must force the AppleTV4K to do Dolby 5.1 as I described above within the AppleTV settings control (restated from the referenced thread)
Please elaborate on what is incorrect
i will add the screenshots in the referenced thread show AUTO for the “Digital Sound Out” whereas everything I read says that should be set to “Pass Through” I don’t think it mattered (?) in that case as user clearly shows Dolby Atmos as end result.
I disagree and must be missing your point.
I got that information from the other thread.
It worked.
You must force the AppleTV4K to do Dolby 5.1 as I described above within the AppleTV settings control (restated from the referenced thread)
Please elaborate on what is incorrect
i will add the screenshots in the referenced thread show AUTO for the “Digital Sound Out” whereas everything I read says that should be set to “Pass Through” I don’t think it mattered (?) in that case as user clearly shows Dolby Atmos as end result.
You wrote, “So in meantime no Dolby Atmos”. That is wrong. The user was me -- those are my screenshots. Atmos works - use those settings. The issue is that the TV’s auto mode isn’t working right with the latest firmware update and Sonos’s current lack of support for LPCM. Therefore, you have to manually switch between DD 5.1 and Atmos. I trust you also created an account on the LG forum to complain to LG too? It is their firmware update that broke it. It was working fine before...
I see - thank you
What an 8th level of Dante’s hell.
It’s there once you read entire thread and all replies enough for context (for me reading entire thread twice helped as learned more on second pass after initial pass - most of this was all new to me… after that thread and many other external sources… I know more acronyms and tech info than I ever wanted or thought I needed to know). Lot of work for a consumer just wanting a good picture with sound absent of hardcore setups.
Maybe pull your reply as a separate thread? It’s helpful and only success I’ve found. Thanks for posting it and jumping in here too.
Everything on web I found keeps saying “pass through“ as the setting, particular for ARC and eARC. You do that and no voices (at least for me on my LG C9) through AppleTV4K. Doing “auto” on the LG end as you say fixes that. So did the Dolby 5.1 force above on the AppleTV4K end. Two different ways that enable voice in movies through apps on AppleTV4K … but as you point out the AppleTV4K path leaves you no shot at Dolby Atmos for the instances you can do it through AppleTV4K. If I understand things correctly, the optimum is just leave AppleTV4K to Atmos and the LG to Auto… now best of both worlds. I’m back to Dante’s 8th level… what a mess!
I did appreciate some of the other posts in that thread as frustration. It is bizarre nothing works right now as advertised if you own a LG OLED C9, AppleTV4K, and Sonos Arc without unnatural work arounds that are next to impossible to find leading me to the desperation of my post for help.
The other useful post IMO was Sonos recognizes problem and working on update per an email from an exec to one of the posters on that thread.
Seems like product may have been rolled out a little early
I managed to get voices back (albeit it plays Stereo 2.0) and Dolby Atmos by setting Passthrough but DISABLING eARC.
Absolutely gutted that I can’t play 5.1 from Apple TV 
I don’t understand why would this be a codec support from Sonos perspective though: if I force Apple to play only 5.1 it works fine, why would it use different way of sending 5.1 audio in Auto mode…?
My setup is AppleTV4K -> C9 -> Sonos Arc. The sonos is connected to the eARC port on the C9 and eARC is enabled. When I select Bitstream and passthrough on the C9, and play a 5.1 source on appleTV eg from Netflix, the Sonos Arc only plays left and right channels and reports it is seeing Stereo 2.0 signal format. The center and surround channels are mute or missing. To work around, I must select Change Format on the AppleTV audio menu and force it to 5.1. It works for 5.1 but it prevents Atmos from working on the Sonos Arc.
So my question is: is the C9 sending the wrong format flags to the Sonos, ie it is sending 6ch LPCM but the format flag says stereo 2.0, so the Arc only plays 2.0? Or is it sending the correct format flag and 6ch LPCM, but the Sonos Arc doesnt support 6ch LPCM yet so it "falls back" to stereo 2.0 and doesnt play the signals on C, LS and RS channels?
This was not an issue with C9 firmware 4.70, why oh why did I click Update and now I am stuck with 4.80 and this broken mess? Why oh why won't Sonos finally release the code that supports 6ch LPCM on the Arc? These are the questions.
My setup is AppleTV4K -> C9 -> Sonos Arc. The sonos is connected to the eARC port on the C9 and eARC is enabled. When I select Bitstream and passthrough on the C9, and play a 5.1 source on appleTV eg from Netflix, the Sonos Arc only plays left and right channels and reports it is seeing Stereo 2.0 signal format. The center and surround channels are mute or missing. To work around, I must select Change Format on the AppleTV audio menu and force it to 5.1. It works for 5.1 but it prevents Atmos from working on the Sonos Arc.
So my question is: is the C9 sending the wrong format flags to the Sonos, ie it is sending 6ch LPCM but the format flag says stereo 2.0, so the Arc only plays 2.0? Or is it sending the correct format flag and 6ch LPCM, but the Sonos Arc doesnt support 6ch LPCM yet so it "falls back" to stereo 2.0 and doesnt play the signals on C, LS and RS channels?
This was not an issue with C9 firmware 4.70, why oh why did I click Update and now I am stuck with 4.80 and this broken mess? Why oh why won't Sonos finally release the code that supports 6ch LPCM on the Arc? These are the questions.
There’s new firmware do C9 in the last couple of days 5.00.03 that may have a fix, but you need to try yourself as I no longer have the Arc…
TV says to Apple TV and other devices: I now support LPCM. So they send such signal. TV can decode it but in pass through mode it just sends it straight To Sonos who’s like “I don’t know that”. In Auto out mode, TV _should_ encode audio to what Sonos knows, like DD5.1 but it doesn’t in 4.8 firmware.
C9 firmware 5.00.03 works the same as 4.80 as far as I can tell. Just waiting on Sonos for the real fix here. I saw a tweet that said it was being tested and is due out “next month”.
C9 firmware 5.00.03 works the same as 4.80 as far as I can tell. Just waiting on Sonos for the real fix here. I saw a tweet that said it was being tested and is due out “next month”.
THanks for checking.
Care to show the tweet maybe?
It would make sense: PS5 uses LPCM as far as I know, would be a disaster if players could only get stereo out of Arc
