The Sonos Arc now supports multichannel LPCM audio. So with the correct settings on your TV and UHD player, you should be getting lossless 5.1/7.1 PCM audio from all of your DTS-HD Master Audio encoded discs which sounds just as good. Sonos probably won’t support DTS anytime soon so you will have to settle with 5.1/7.1 PCM with your DTS:X encoded discs too.

Thank you for your answer.

I will try that setup in the bluray, but I have only two options there,  either bitstream or PCM. Do I have to setup something in the ARC ?

Set DTS to PCM on your UHD player and test it.

To see what audio the Arc is receiving on the Sonos app, go to System > About My System > scroll down to the Arc information and see what it says after “Audio In:” If the settings are correct, when you play a DTS-encoded disc, it should say “Multichannel PCM 7.1” or “Multichannel PCM 5.1”. If the settings are wrong, it will say “Stereo PCM 2.0”.
 

If this doesn’t work, we can look at your TV audio settings. What specific TV model do you have?

I just test Tenet with DTS and it says Stereo 2.0

I have a LG OLED 4K Dolby Atmos 

What specific LG model?

It could be an issue with your LG TV. Other LG owners have had problems specifically with Panasonic UHD players. Here is another thread with LG/Panasonic UB820 UHD owners who are having the same problem with PCM audio:

https://en.community.sonos.com/home-theater-228993/lg-c9-arc-ub820-multichannel-pcm-for-dts-blu-ray-discs-6850976

Hi 

My TV is an LG OLED65B7D . I tried with my PS5 and is the same, PCM stereo 2.0 

With my XBOX X series I can't even listen anything. 

Does your LG have HDMI eARC or just HDMI ARC? When you said in your original post that Dolby Atmos from UHD discs sounds amazing, are seeing the Dolby Atmos logo on the Sonos app? When you look under About My System does it show Dolby Atmos (TrueHD) after “Audio In:”?

Hi 

Yes, it is eARC . Finally I solved it,, somehow. The only way is by my XBOX Series X. Using the dolby application and setting output in the consolé to dolby atmos.

Then in menu devices -- bluray , unselect the option to let encode audio to the device. Thereby, the Xbox does the trick. 

I am watching Tenet which has DTS X audio and my Sonos app shows Dolby Atmos and in about my system shows it too. The sound is really amazing 

I did not find a way to do the same neither with my Panasonic bluray nor with the PS5, though. 

Really appreciated for the help and support 

Thank yiou

Glad you got it working on the Xbox. You probably aren’t getting Dolby Atmos audio from the Tenet disc even though that’s what the Sonos app says. The Xbox probably either is converting the DTS track to Dolby Digital or it is playing multichannel PCM and the Sonos app isn’t identifying it correctly. Either way, as long as it sounds good, that’s all that really matters in the end.

Just curious… what audio does the Xbox say it’s playing while you are watching the film?

Hopefully LG can fix their PCM issues so your Panasonic UHD player will work with your TV in the near future.

Hi

The XBOX is set to bitstream with output Dolby Atmos. This setup only works if the Dolby App is installed and setup for home theater. You then must unlock tge property to allow XBox to make the conversion 

Both tge Sonos app and the XBOX say that is Dolby Atmos.  Anyway, the difference between playing this here compared to the PS5 or the Panasonic is unbelievable. 

Probably you are right and it is not true atmos, but I have all kind of effects and I hear sounds isolated in the rears. 

Why would it not be true Atmos? If Sonos says it's receiving Atmos, I'd believe it.

Because the Tenet UHD disc only has a DTS-HD Master Audio track, not a Dolby Atmos track. And the Xbox isn’t capable of converting DTS to Dolby Atmos.

So what device is supplying the wrong info?

Could it be possible that the Dolby Software is doing the transformation?

I mean  it is quite strange that both the Sonos app and the XBOX are saying that is Dolby Atmos

I think this is a problem with Xbox showing everything as Dolby Atmos when it is not. I have seen this being reported on other forums. More than likely, the Xbox is converting the DTS-HD Master Audio track to Dolby Digital 5.1 or PCM 5.1. And since Xbox is saying that it’s Dolby Atmos, the Sonos app is just displaying what the Xbox is telling it to display.

Well, your explanation sounds logical. Actually,  I just watched Prometheus, which has a DTS X soundtrack,  and then Alien Covenant which is Dolby Atmos. 

Although the XBOX is telling that both are Atmos, same as the Sonos App, there is quite a difference . You can feel it. 

Anyway, even though,  it's still much better than the PCM 2.0 I got from both my Panasonic bluray and my PS5.

Are you watching Prometheus on 4K UHD? Because I think it just has a DTS-HD Master Audio track.