@FishyD I have a DTS demo Blu-ray disc coming next week that includes a 7.1 “DTS Sound Check” video. I’ll report back how the Arc handles the surround test tones from the 7.1 PCM signal.

I just performed the “DTS Sound Check” from a 2015 DTS Demo Blu-ray disc. I am playing this on a Panasonic DP-UB820 UHD player with DTS set to PCM. These are the results:
 

DTS Sound Check 5.1
All channels played the test tones correctly. The Sonos app reported “Multichannel PCM 7.1”.

DTS Sound Check 7.1
All channels played the test tones correctly EXCEPT the Left Rear and Right Rear Surround channels. The surround test tones only played out of the Left Side and Right Side Surround channels. The Left Rear and Right Rear Surrounds were completely silent. The Sonos app reported “Multichannel PCM 7.1”.

So it appears the Sonos Arc is not playing the Left Rear and Right Rear surround channels when playing a DTS-HD Master Audio 7.1 track.

@GuitarSuperstar Is there a setting on your BR player to force a 5.1 output? Just out of curiosity, that fixed this exact issue in my experience. Do ARC/eARC sound bars use EDIDs or some kind of config file to tell TVs what their capabilities are? I wonder, is the problem that Sonos isn’t giving proper format instructions to upstream devices or that the sound bar isn’t properly mixing 7.1 down to 5.1. 

I just performed the “DTS Sound Check” from a 2015 DTS Demo Blu-ray disc. I am playing this on a Panasonic DP-UB820 UHD player with DTS set to PCM. These are the results:
 

DTS Sound Check 5.1
All channels played the test tones correctly. The Sonos app reported “Multichannel PCM 7.1”.

DTS Sound Check 7.1
All channels played the test tones correctly EXCEPT the Left Rear and Right Rear Surround channels. The surround test tones only played out of the Left Side and Right Side Surround channels. The Left Rear and Right Rear Surrounds were completely silent. The Sonos app reported “Multichannel PCM 7.1”.

So it appears the Sonos Arc is not playing the Left Rear and Right Rear surround channels when playing a DTS-HD Master Audio 7.1 track.

Is the DTS 5.1 reporting as multichannel pcm 7.1 correct then, or should it be multichannel pcm 5.1?

All my devices that output 5.1 such as blurays with DTS 5.1 output as 7.1, even on my series x outputting as uncompressed 5.1 says 7.1 on the app. 

@ledzep1 He played a 5.1 test sound, it doesn’t necessarily mean the BR player was outputting a 5.1 signal. The BR player could be having the same issue as our PS4s/5s where for whatever reason it recognizes Arc as 7.1, outputs a 7.1 signal and Arc doesn’t convert to 5.1  If he can manually set the BR player to 5.1, that would eliminate that variable.   

In my experience across 3 devices now, devices outputting LPCM 5.1 show properly in the Sonos app as PCM 5.1. I think it may be your TV model/settings that is the problem there. What are your pass through settings set to?
 

There is still definitely something odd though with devices thinking Sonos is 7.1, I think. 
 

My PS5 when forced to output uncompressed 5.1, shows correctly in app as 5.1. When allowed to pick itself on “auto” it shows 7.1 in the app. 
 

Did you try that ATV 5.1 test app? 

Need to get around to trying the test app, on my series x if I elect uncompressed 5.1, the sonos app says its outputting as multichannel pcm 7.1.

I know others have encountered the same, so its not just me, perhaps it is the LG CX, I have audio set to passthrough with eARC on.

@FishyD I tried test app and it reports multichannel 7.1.

@ledzep1Interesting. That is a DD 5.1 signal and if your ATV is set to “auto” in the sound settings, is decoded by ATV and output in LPCM. That pretty much narrows this particular issue to LG, that is the only variable here. With this exact same test, my Sonos shows PCM 5.1. I would just make sure your ATV sound is set to “auto” and shows in the description that ATV will output in multichannel PCM. 
 

I wonder if others having this problem have LGs. 
 

On my Sony, same settings. Pass through and eARC on. Do you have an “auto” setting on your TV in the audio Arc pass through settings? Maybe try that and see what happens. 

Yep it’s set to auto, yes others have this issue, I’ve got responses from others on another forum and there are a few threads on Reddit reporting same, so seems like a LG issue but It seems to have got mixed up with that other LPCM audio issue on here that Sonos are investigating.

100%.  There appear to be 2 separate (possibly related) LPCM issues here. This one you and others are having where on LGs, an actual 5.1 signal is somehow showing as 7.1 and the issue where devices like PS are auto recognizing Sonos as 7.1 and Sonos isn’t converting that 7.1 down to 5.1. 

There isn’t a setting on my player to force 5.1.
 

If Sonos decides to fix the down mixing, that would be great, but honestly I am not too bothered by it because the rear surround speakers still sound great when watching a DTS movie. And if they fixed it, I’m not sure it would make much of a difference for most content.

I have an issue here with my pc and Sonos 5.1 system.    Lg cx connected to Sonos arc directly via earc. Dolby atmos videos work fine and even 5.1 Dolby tracks (though it says Dolby multichannel pcm 5.1, but whatever ).  
Now the problem I can’t solve, why I can’t play any games in PCM 5.1.  The Sonos app says it is playing pcm 5.1 or 7.1 but rears are not working properly. Rears only turn on when there is a sound in video game that turns on all speakers like an orchestra or certain game music. 
 

I have tried switching to auto or passthrough and still same problem. It seems like others have similar issues but anyone with video game issues like mine ?

You have PCM sound issues while the Sonos app shows 5.1? That doesn’t track with any of the issues mentioned here that I saw. If the issues are with PCM 7.1 showing then yes, we all have had the same issue, check out the last few pages. You need to force your device (PC, assuming this is what you are gaming on?) to output in LPCM in 5.1. In my experience with PS, if you do that and the Sonos app says 5.1 PCM it should be good to go. There also seems to be another possibly unrelated issue with the LG CX. A few guys above are having issues with 5.1 signals showing as 7.1 (in app) that at least for me, do not exist (Sony TV). If you can’t force 5.1 on your PC, maybe just use DD. That is what I did with my PS4 before I swapped to PS5 and the option to override and force a configuration output showed up. 

OK so I did a recheck. Your right FishyD, I have the same PCM 7.1 issue and the channels are way off, and not accurate. I can not do DD on PC games, they are all in PCM, so I don’t know about forcing 5.1 LPCM (I don’t even know how to do it). In Windows, 5.1 and 7.1 are greyed out, only time sounds works is if i use “dolby atmos for home theatre” or Stero (showing as PCM 2.1). If I restart, for some reason i get option to do 5.1 or 7.1 select, but this produces no sound in my games and youtube. This is so frustrating….

@Basid786 that is really frustrating. I was hoping that somehow you could force your PC to output 5.1 LPCM like I did on PS5. Or make your motherboard convert the game’s PCM to DD for an output (this worked on PS4). I haven’t played PC games in a while so I’m out of the loop on sound setups there. 
 

Perhaps some kind of software could take over Windows control of audio output? Check out this thread. It is somewhat related (forcing 5.1 PCM output over HDMI). https://www.reddit.com/r/htpc/comments/77ixil/can_i_force_windows_10_to_output_51_pcm_to_my/?utm_source=share&utm_medium=ios_app&utm_name=iossmf
 

The software is Equalizer APO. Never used it, no idea if it would work but there has to be a way on PC to do it somehow. 

So i did alot of reading. No point in getting that software as all PC games output to 5.1 PCM.  I’m lost here. So frustrating. I got E-Arc, LG TV that supports HDMI 2.1 and Sonos Arc but it wont ouput 5.1 PCM on the PC. 

Any updates from Sonos on fixes for the LPCM issues, there was a tweet a while back that they are in active testing for the fixes. I guess they want to be sure any firmware in testing is working correctly, but jeez do they take there sweet time to fix things, this Sonos ARC will be ancient the time its working correctly.

Sonos just put out a 13.0 firmware release

@ledzep1 , @GuitarSuperstar - any chance you can check if this has fixed the LPCM 7.1 to 5.1 downmixing issues?

Based on the release notes, it doesn't appear so…

I updated the firmware and played the 7.1 audio test on my DTS demo disc… no change. Both side surround channels play the test tone, but both rear surround channels are silent.

Did Sonos ever acknowledge the downmixing and volume level issues?

Yes I believe so, I think someone on here tweeted the Sonos ceo and he responded that they are working on it, I may be wrong though.

Not so sure about any acknowledgement about the volume level issue…

Did Sonos ever acknowledge the downmixing and volume level issues?

Yes I believe so, I think someone on here tweeted the Sonos ceo and he responded that they are working on it, I may be wrong though.

Not so sure about any acknowledgement about the volume level issue…

 

December 4th, lol.

I’m sure there was another tweet someone from sonos technicians that they have this fixed partly and its in testing.

I do find it quite poor this company takes so long to fix issues. I do realise we are in a pandemic, but sonos support who I guess work from home could keep us updated more on progress for fixes to issues.

For what it’s worth, I have heard from their home theater product manager that the plan is for it to be included in the July release.