Sonos Arc and 7.1 Downmix to 5.1

So thanks for remaining engaged on this topic but wouldn’t it be relatively straightforward to test whether this is the case or not? If all is ok then no need for a fix and these topics could be put to bed?

Hi @ste_ms 

Earlier, you mentioned that you don’t actually have surrounds. We tend to troubleshoot problems that customers are actually experiencing - it’s not that I’m trying to be dismissive here, but if I was to ask an engineer to do a suite of tests with various input devices and TVs for a particular problem, they’d want to see that all possible troubleshooting had already been done, and they’d want to see multiple diagnostic reports taken at various points throughout. They’d probably want video evidence too (if practical). Personally, I cannot do any such testing as I do not have a PS4/5, an LG TV or indeed a Sonos home theatre product (I’m working-from-home).

I do appreciate that you are doing the sensible thing and researching possible issues before buying surrounds. If more people had done as you are doing prior to buying the Roam, for example, there’d be less angry voices about how it doesn’t support being a part of surround sound. Sonos has an excellent Money-Back-Guarantee programme for just this kind of eventuality. I recommend you buy the surrounds and try it out - if you find a problem, ask for help. If help isn’t helpful enough, get your money back by returning the speaker - in the UK, you’ll get 100 days to try things out.

Incidentally, we’re still off-topic on this thread. As I mentioned, this thread is for 7.1 downmixing. I suggest you start a new thread if you want to talk about 7.1 being mis-reported in the Sonos app (if, in fact, that’s what’s actually happening - personally, I doubt it. It seems more likely that the TV or source is responsible). Further off-topic discussion here will have to result in this thread being closed so that searches stay relevant.

Edit: I do understand there is an obvious thematic link between 5.1 tracks being transformed into 7.1 tracks prior to arriving at the audio device, and 7.1 tracks being downmixed to 5.1 in the audio device, but these are technically very different - especially as the former is not something we can actually address. 

Fair enough but would you be able to check out the other threads on this topic and perhaps see if you could get an update for the community? I don’t have surrounds but that doesn’t mean the sounds aren’t being handled incorrectly within the beam as it obviously plays back all 5.1 channels itself. Thanks.

As someone who has done a lot of looking into this issue and had an LG C7, LG CX, LG G1, Sony A8H, Sony A90J and Sony A80J I am well versed in this issue, Your comments to a lot of people in here are half correct, but aren’t really helpful as Sonos has not been overly clear on the issue, and in particular with LG - Sonos issues, neither LG or Sonos has ever really been clear with people where problems are happening. There is a real history of LG and Sonos not playing nicely together, going back to lip sync issues as well.

The LG CX and C1/G1 series have had the LPCM 7.1 issue with the Sonos Arc ever since LPCM support was added to the Arc. It appears the Arc is either not correctly advertising it’s LPCM support to the LG or the LG is not reading it’s capabilities properly as it sends a 7.1 signal whenever MultiChannel PCM is concerned. This is a dealbreaker as even though some people claim to not notice it, it messes the whole surround experience up.

The Sony A8H, A90J and A80J do not have this problem. The Sony’s and the Sonos appear to communicate their capabilities correctly and the Sony sends a MultiChannel PCM 5.1 signal correctly. The A80J/A90J have a seperate issue with the Sonos Arc in which the TV will randomly switch from an eARC connection to an ARC one, however this is infrequent, fixed by toggling eARC off and on in the TV settings and is nowhere near as detrimental to the listening experience as the LG LPCM 7.1 issue.

It needs to be made clear that this is specifically an issue between newer LG TV’s and Sonos if any progress is going to be made in resolving it.

@billiejoe87 I have also noticed my A90J randomly behaves as if it is an ARC connection (rather than eARC), with a toggle needed to fix it. How did you diagnose this issue? Or is it just something you assume is happening based on the exhibited behavior? Along those same lines, have you tried another eARC supported device? I’m wondering if this is a Sony issue, or a Sonos one.

I diagnosed the issue by checking the Sonos App and realising I was getting Atmos delivered by Dolby Digital Plus via the Apple TV which ussually sends it as full Dolby Atmos over eARC. I also noticed the PS5 and Nintendo Switch were no longer sending MultiChannel PCM 5.1 and instead were sending Dolby Digital Plus 5.1 which is what the TV converts the audio to if it only has an ARC device connected. Toggling eARC off and back on is what fixed the issue in all cases.

Actually suprising that more people don’t talk about it on the Sonos forums as it’s a very well known issue over on AVS Forums and it appears to also be happening with a few different AVR’s. I assume most people here must never check the app and confirm what audio format they are getting.

@Corry P , thank you for giving this topic so much attention. I’ve been really looking forward to the Sonos implementation of downmixing lpcm 7.1 to 5.1; it should only help the situation if 7.1 is being improperly sent through from a source tv. Then the app would no longer have need to display lpcm 7.1, which the arc/beam and 2 rear surrounds does not support anyway. This is confusing to the consumer regardless of whether anything is wrong or not and regardless of which source is at fault if anything is wrong.

I have been following and posting on the topic periodically for almost a year. I have an LG G1. I’m typically only affected by this when watching non-Dolby audio discs through my ub9000/PS5 or when playing games in surround on the Nintendo Switch. I have the Arc, two rear Ones, and a Sub.

I’m happy to do some diagnostics if it ever did come to that. Thanks again for your time.

Hi Everyone,

Well, this is embarrassing!

After some investigation, I’ve found that downmixing of 7.1 channel LPCM to 5.1 channel LPCM was indeed implemented on the Arc as a feature last year, but our literature wasn’t properly updated to reflect the change.

To be clear, the Arc does downmix 7.1 LPCM to 5.1, has done for some time, and we are working on updating our documentation to reflect the fact. Beam (Gen 2) has always supported LPCM and has always downmixed.

Thank you all for pointing this out to me so we can now make sure that this information becomes public. I’m sorry for the unnecessary confusion. I’ll post this in multiple threads.

This other issue with LG TVs is unrelated, but we’d very much like to get on top of it. We’ve requested the investigation of LPCM channels being played from the wrong speakers when an LG TV is involved, specifically when 7.1 channels are reported, and we will reach out to LG with details once we’ve gathered some solid evidence for them. Therefore, we’d very much appreciate it if anyone affected by this specific issue would visit this new thread I’ve made for gathering some details. Thank you.

 @Corry P

Thank you very much for clarifying this here and in other posts.  As a request going forward, I really do wish Sonos would reconsider their practice of generically describing bug fixes as only “Bug fixes and performance enhancements” in their release notes when it includes significant fixes that have been raised in multiple posts here over several months. It would go a long way to help avoid confusion like this in the future.

@billiejoe87 would you mind sharing the link to the thread over on AVS Forums? I’d love to be able to  contribute/participate in the discussion over there.

Along those lines, have you noticed your A80J/A90J produce subtle popping noises when outputting LPCM from the Apple TV (via the Arc)? It seems to only occur with LPCM, and not encoded audio (Dolby/DTS). It isn’t loud, but more like a soft pop when switching audio codecs, turning the Apple TV off, etc. A great way to demonstrate the issue is browsing around Netflix, and allowing the previews/trailers to play. More often than not, an initial soft popping sound can be heard.