LG C9 + Arc + UB820 / Multichannel PCM for DTS Blu-Ray discs

After reading and troubleshooting for a long while, it seems that a setup of an LG 2020+ TV, a Sonos Arc, and a Panasonic ub820, you cannot get DTS to play as anything other than stereo without using an Arcana or something similar. Super frustrating, audio is one of those things I just want to work without fussing around with settings. In my case I have a PS5, so I guess I’ll be using that from now on for any disc with DTS. Unfortunate that I can’t use an otherwise amazing player for all my discs, unless I wanted to shell out another $250 for the Arcana.

The not-so-rare cases of a disc having Dolby Vision and DTS do sting.

Ya it is completely stupid that this couldn’t have been fixed by LG/Panasonic, not sure who the culprit is I forget after not reading up on this stuff in some time.  However what I ended up doing was bought that Sony X800M2 from Best Buy when it was on sale for $200 or less some time ago.  Thought it’d be annoying to have 2 but not really, and it’s the cheaper and cleaner alternative over the Arcana or that way overpriced Arcana Vrroom.  I have played a ton of discs in the Sony and have so far not had any issues, so I’ll keep my Panasonic UB820 obviously for disks with Atmos + DV and also since I have custom RF firmware on it I’ll keep for region B/C disks.

I have the same equipment as the OP (C9, Arc, UB820).

If I have a disc with DTS-HD, am I better off getting the UB820 to…

1. Downmix to DTS and send it as bitstream

or…

2. Don't downmix and send it as PCM

Which is better from a quality standpoint?

If you can’t get the UB820 to play “Multichannel PCM” audio from DTS discs with option 2, then option 1 is your best choice.

I just wanted to add a little more info here:
 

I have a C9, Sonos Arc and had the Panasonic 820. While many DTS UHD discs has a core lossy stream (Gladiator plays perfectly fine on my setup for example in lossy DTS 5.1), all releases from Arrow Video don't. Both Donnie Darko and Pitch Black only has a lossless DTS stream, and won't output any audio when playing the discs. The only option is to turn on PCM, but that only gives you 2.0 audio.
 

I returned my 820 and went with the Sony 800m2. Seems like the best option now. Or an Xbox. 

I have never been able to pass LPCM 5.1 7.1 from the Panasonic 820 through my LG CX to Sonos ARC. only PCM 2.0. Thanks to someone else’s post in this community, I found the very affordable $150 Sony X700/M player w/ great IQ BTW will pass LCPM 5.1/7.1 from the player through the LG CX TV and to my Sonos Arc for my DTS: HD only blu-rays. It was too late for me to return the Panasonic, so I use the Panasonic 820 for all my Dolby Atmos blu-rays discs HDMI 3 and the Sony player for DTS only blu-rays HDMI 4. 

FYI - LG have just released an update for the CX (04.40.10) which appears to (mostly) resolve this issue. 

Before, I only got stereo PCM passthrough from the 820 for DTS discs - and had to get the HDFury Dr HDMI 4K and code with a custom EDID to get the full LPCM 5.1/7.1.

However - with the new LG update I can get LPCM 7.1 passthrough without the need for the additional Dr HDMI 4K device. For some reason, the Sonos app is still saying that it’s LPCM 7.1 (rather than LPCM 5.1) - but I guess this shouldn’t be a problem since the ARC is now able to downmix from 7.1 to 5.1 correctly.

N.B. - if I set my Xbox Series X to uncompressed 5.1, the Sonos app now says LPCM 5.1 (before it said LPCM 7.1) so I know it can work as it’s meant to! It must mean that there’s still something not quite right in the interface between the LG CX and the UB820 to cause the UB820 to put out 7.1 instead of 5.1 - but as I said, at this point it doesn’t really matter as what we hear should be the same anyway.

It would be great to hear if this works for anyone else who had the same issue with the LG CX and the UB820! 

I can confirm your findings on latest 4.40.10 firmware for CX. With my particular devices I never had a problem passing LPCM, but I always got multichannel pcm 7.1

Xbox series X when set to uncompressed 5.1 now correctly states multichannel pcm 5.1 (before it said 7.1)

My Apple TV 4K still says multichannel pcm 7.1 for all 5.1 content though.

So there has been fixes, but its weird that some devices still report differently.

@Woj  / @ledzep1

Hello. Are you already running on Sonos 14.10? If you have time, can I please ask for you to set your Xbox to uncompressed 5.1 and have it run for like 2-5 mins and see if you encounter audio dropouts? Just ensure that the Sonos app reads the audio format as “Multichannel PCM 5.1” the entire time.

Reason I’m asking is I’m having issues post-14.10 where Multichannel PCM 5.1 drops out once every 1-2 minutes. I’ve tested on PS5/PC→ LG C1→ Beam 2 (so could be a me / beam only problem). PC set to Dolby Atmos for Home Theatre reads on the app as Dolby Atmos (MAT) with no dropouts. PC and PS5 set to LPCM 7.1 ch reads on the app as Multichannel PCM 7.1 with no dropouts. However, PC and PS5 set to LPCM 5.1 ch reads on the app as Multichannel PCM 5.1 with the aforementioned dropouts.

So this only happens when the Sonos is receiving the Multichannel PCM 5.1 format. I came across this issue while using my PS5 as a bluray player where I transcode DTS-HD MA 5.1 to LPCM 5.1. 2 weeks ago, a couple of days before the Sonos 14.10 update, I was able to watch a bluray at Multichannel PCM 5.1 without any issue. Then yesterday, I tried watching another film and encountered the dropouts. The only difference with my setups is the Sonos has since updated to 14.10 so I’m inclined to believe that it’s the culprit.

If this is too off-topic, perhaps you can send me a PM for your response. Thank you. 

My setup is Sonos Arc (14.10 firmware) + LG CX (04.40.10 firmware) + Panasonic 820. After updating to those firmwares the Sonos app is now saying Multichannel PCM 7.1 (and the sound output sounds multichannel now too). My audio settings on the CX and 820 are set to their respective defults. Glad to be able to finally use my equipment fully.