Okay, so I fix it by myself. It wasn’t a Sonos issue but an LG issue. I saw that a lot of people with that issue own an LG TV. So I look for more information on that. I found an issue on Reddit link to 5.1.

What I did on my LG C1

• Remove my Sonos Beam from the external output as a sound bar
• Reconfigure Sonos Beam as a sound bar (Sonos is not directly proposed by LG you have to enter the brand in the search bar)
• Uncheck one of the conditions of use to reboot of my LG. 

Since I don’t have issues anymore and that without reset!

WebOS version: 03.33.11

Sonos version: 14.18

I got the HDMI cable today and all problems seem to be solved. Thank you so much!!

All - I just want to summarise and clarify my workaround.

The audio drop-out is assumed to be when the Beam Gen 2 communicates with the TV, causing the TV to trip over and drop the audio for moment. This only seems to happen on HDMI 3 or 4 and when playing 5.1 PCM audio. The most common sources of this audio type include the PS5, Nintendo Switch and the Apple TV 4K 3rd Gen.

Although I linked a specific one way fibre-optic HDMI cable that I bought and confirmed fixes the issue for me (or more correctly, provides a work-around), I believe that any similar HDMI cable should work.

My understanding is that these cables do have some copper wires in them for certain elements of the HDMI signal, but some parts of the signal go down the fibre-optic part. The fibre-optic part is one way only. The TV needs to be at the source end of this cable and the Beam Gen 2 at the other.

It seems the signal the Beam Gen 2 sends to the TV which is assumed to cause the drop-outs, is trying to go the wrong way down the one way part of the fibre-optic HDMI cable and therefore doesn’t get through to the TV, resulting in the audio signal from the TV not being interrupted. I can’t really explain exactly what is happening as I don’t really understand how HDMI works (there are others on here that know much more than me and my interpretation of the fix may be completely wrong anyway), but as an engineer that has experience troubleshooting stuff, I thought this had a chance of working, so I tried it and was successful.

It is great to see people posting on here that have tried this and also had success. Hopefully this won’t stop Sonos from implementing a proper fix in the future as I’d wager a lot of Beam Gen 2 sound bars have already been returned due to owners thinking they are faulty - most people aren’t going to try and troubleshoot or search for fixes online. At least we now have this workaround to keep us going. Many thanks to other posters on this thread that also helped narrow this down.

Just got off the phone with Sonos Europe tech support (over one hour call). I sent them the diagnostics and described the issue including all of the steps to reproduce it, faulty setup and everything everyone mentioned on the thread to solve it. I also gave them the link to this thread and asked that the support staff comment on it. He could not (obviously) help me solve the issue but he escalated it to L2 and they will look into it. I explained how frustrating it is that such a high end premium product performs so poorly, and how bad the lack of support and acknowledgment on their side is. I made them promise to respond in this thread to keep the community in the loop as they’re working to fix this issue, and keep me updated on the case.

Having had experiences with customer service before I cannot guarantee this will help in any way and this issue will actually get fixed, but at least it’s something, and maybe it’ll be the spark that will make them look more seriously into it.

I observed two new things today:

1. I had the opportunity to swap out the Beam2 out for an Arc in my setup and compared the 11111 diagnostics for "Sonos test card" on HDMI2 over an unmofidied cable. There is a difference in the reported audio formats (albeit that both have silent audio):

    Arc: PCM 2ch 0Hz | N:0, CTS:0, LayoutValue:0, Channel Status: 2
    Beam2: UNKNOWN 9Ch 88200Hz | N: 6262, CTS: 42092, Layout Value: 0, Channel Satatus: 9

2. I finally got round to splicing a Rapsberry Pi TMDS video signal with the Beam 2 control/eARC signals. Pins 1-12 connect the RPi to the TV which replaces the Beam2 test image with the RPi console. Pins 13 to 19 connect the Beam2 to the TV's CEC, DDC and eARC. On power up, the TV was using CEC to operate the Beam2 volume, which was a good start, but needed tweaking to get the setup operating like for like:

• toggled "eARC Support" off/on in the LG TV as it had fallen back to ARC mode (LPCM 2.0) despite indicating that eARC was enabled. Once eARC was re-negotiated LPCM 5.1 played from the HDMI3 source.
• used tvservice command to force enable the RPi HDMI output - since it has no DDC wires connected and therefore no EDID, the RPi doesn’t know what resolution to use so disables HDMI. Mode 34 sets 1080p@30Hz (same as the Beam2 test image):

sudo tvservice -e="CEA 34 HDMI"

At this point, choosing HDMI2 on the TV showed the RPi video signal. Then, switching the TV input to HDMI3 plays LPCM5.1 out of the Beam2 with no dropouts. I can change HDMI2 video modes in the "background" with tvservice (e.g. 720p or 24Hz) without interfering with the eARC audio stream. However, given the observation in #1 I thought I'd try to get the RPi to output 8ch audio into HDMI2, as currently the audio stream is disabled entirely (as per ARC).

I changed input back to HDMI2 and used speaker-test (as I had previously to force 8ch sound). I was surprised to hear it play out of the Beam2, but I guess this should be expected - the TV is just routing the audio received from the selected HDMI input into its eARC circuit and back out to the soundbar, just so happens that it's the same HDMI port for both in this case. I switched back to HDMI3 and Beam2 played LPCM 5.1 without dropouts.

sudo speaker-test -c8

Then I thought I'd change the HDMI2 audio from 48Khz to 88.2Khz (to match the Beam2 diagnostics) and a dropout occurred immediately, but did not repeat. I quit speaker-test and restarted, another drop out. I repeated this and checked on HDMI3 11111 and could see the audio format blip occasionally, in the same way as when the Beam2 drops out.

With the sacrificial cable in this new configuration I can also patch the Beam2 video signal back in to the TV. There's a drop out as soon as the connection is made, then repeating every 59 seconds.

I repeated the tests with the same source on HDMI1: no dropouts (as previously discussed), even when trying to force them with speaker-test.

I repeated the tests with the Arc, no repeated dropouts but I could force them with speaker-test when the LPCM5.1 source is HDMI3 and the video spliced to the RPi (and could not when the source was HDMI1).

I'm thinking that #1 and #2 mean Beam2 is doing something unusual to the audio signal in its "test card" output (into HDMI2) which the LG TV is sensitive to on HDMI3. I can't tell what the odd behaviour is, whether it's close to tolerance, undefined, invalid or just dropping/handshaking. Whatever it is, LG TV is sensitive to it on HDMI3 but not HDMI1 (anymore).
 

@Corry P any chance of another look at this? Every step seems to have been exhausted in terms of resetting and re plugging.

I have been through every option I can find trying to isolate a cause but nothing fixes it. I measure my dropouts about 40s apart but sometimes a bit longer, completely repeatable. I took this diagnostic after about 5 or 6 dropouts in a row. Would be happy to do any more tests with support if required, thanks.

Diagnostic 1814488426

I can chip in with my experience regarding this issue. I bought a Beam Gen 2 a cople of weeks ago and had the exact same problem. Sound dropouts 1 sec every minute or so when playning Xbox Series X with uncompressed 5.1. Uncompressed 7.1, Dolby Digital and Dolby Atmos worked fine.

I have a LG C1 65” with ultra certified hdmi cable connected between the TV and the Soundbar, Xboxs own HDMI cable connected to the TV. Both the TV and the Beam with the latest firmware. I couldn't figure out what the problem was. I tried everything that I could think of, factory reset, changed cables, diffrent setting on the TV and the Xbox but nothing.

In the end I returned the Beam and bought an Sonos Arc instead and now everything works just fine. No problem with uncompressed 5.1 and I’m using the same settings on the TV/Xbox and the same cables I used for the Beam.

I didn't read the whole thread but It seems a lot of you have an LG TV (including me) so maybe there is a problem with LG and the Beam Gen 2.

i'm sorry I didn’t brought any solution to the table but I hope my input can be of some help for you guys to figure out what the issue can be.

Same exact issue here, PS4 + LG C1 + Beam 2 with Symfonisk Bookshelf surrounds. I've been following this topic for 2 months now hoping for a solution, but since Sonos is showing no sign of solving it I guess I'll add a comment too. I just don't get how this isn't a bigger priority for them? Playing a large portion of Blu-rays on one of the most common TVs is not possible because of this.

I'm just wondering what the most effective way is to let Sonos know how common this issue is. Should I make a separate support ticket for myself?

When I run the following commands on Raspbian on a Raspberry Pi3 with Beam2 on eARC:

sudo speaker-test -Dhdmi:vc4hdmi -c6
sudo speaker-test -Dhdmi:vc4hdmi -c8

the 11111 menu displays either 'PCM 6Ch 48000Hz' or 'PCM 8Ch 48000Hz' during streaming and Sonos app also shows the appropriate Multichannel LPCM mode. 

When speaker-test is killed, Beam2 goes silent, Sonos app format goes blank immediately, 'cat /proc/asound/card1/pcm0p/sub0/hw_params' shows the RPI’s sound card device is already closed, but:

• HDMI1 (not bugged) - 11111 holds the same PCM mode until a different speaker-test format stream is started, up to several minutes later
• HDMI3 (bugged) - 11111 holds the same PCM mode, but only until the 59th second after the previous dropout, then 11111 shows the format being pushed to PCM 2.0, where it then stays (again, until a new speaker-test format is streamed)

The above behaviour is the same for 6Ch and 8Ch, the only difference I observed being that if speaker-test is streaming 6Ch during the 59th second on HDMI3, the Beam2 audio (as we know) is interrupted for 1 second. There is a 59 second event for both 5.1 and 7.1, but it is only audible on 5.1.

Replacing the Beam2 with an eARC AVR - when speaker-test is killed on HDMI3 there is no drop down to PCM 2Ch at 59s, both formats remain until a new stream is started. This doesn't give any indication how Beam2 is involved, but only its presence is triggering the TV into doing something every 59s. I couldn't find any obvious HDMI events/errors (CEC, handshakes, etc) on the RPI at the 59s intervals.

A post I found recently observes the dropout period is not tied to the amount of content played (back when it was approximately 40s):

https://discussions.apple.com/thread/254365553

If I unplug the HDMI cable after killing speaker-test, 11111 shows HPD/5V/etc drop low, Video shows 0x0I@0.0Hz, but audio still holds the most recent PCM 6Ch/8Ch value. This is the same on HDMI1 and HDMI3, for the RPI and PS5 as sources. The TV is not reporting the audio format on the input wire. Rather, I guess it’s whatever the mode the next circuit in the audio path was most recently configured to based on the the last frame of audio received. PCM 2.0 is only displayed again when HDMI cable is reconnected. On HDMI3, streaming 5.1/7.1 then resumes the 59s timer.

The cable arrived today. After a first short test, I can say that the Nintendo Switch no longer has any dropouts. Will check the PS5 later today.
I'll report back here in a few days if everything is still running stable!

Replacement cable arrived today… further testing required, but played an hour of Switch with Surround on, and played 30 mins of a 5.1 Blu Ray that was problematic before… zero dropouts thus far!

Many thanks again to @MJW75  and @RANDUSR23296 

Masking pins 10/12 with a *sliver of tape does seem to have the same outcome, TV no longer recognises the video on HDMI2 (as per 11111 menu) and the dropouts are gone:

This is it happening on my C2. 
 

I purchased the Beam Gen 2 yesterday as my first Sonos product, specifically to use with PS5 and LG C1 48. This is absolutely a specific issue related to the Beam and not LG.

I have used numerous other audio equipment, in a multitude of formats both with PC and PS5. No such issues with any other products. The audio drop outs with LPCM 5.1 are extremely disappointing. It is not acceptable to suggest the purchasing of a non-CRC Hdmi cable, or to switch to a compressed audio format (e.g. Dolby) as workarounds. Further to this, passing the buck to another manufacturer (LG) is not acceptable when there are no reasonable or methodical grounds to suggest doing so. I do hope that this fault is resolved soon, or the Beam will be returned and shall be my last Sonos purchase. 

@RANDUSR23296 has done more than Sonos ever did (w/c is actually nothing). Sad that they can’t even be bothered to lift a finger despite all the evidence shared here by the users.

 To recap, Sonos’ response to this situation after ~1 year and ~400 posts:

1. No technical investigation that cleared the Beam of any fault
2. Place the blame on LG because numerous unrelated results come out when you google for “LG OLED 5.1 issue”
3. Claim that LG will fix it with source being “trust me bro”
4. Refuse to elaborate further. Leave

@ste_ms tagged the mod on a post from a week ago and they have not yet responded. Considering that monitoring this place is literally their job, unless they are on holiday, it is clear that Sonos had already  ducked and ran.

To potential buyers or those within the return period: if you’ve come across this thread, take heed and stay away from Sonos.

I think an internal investigation could have happened (rather than just auto-timing out their Jira ticket after 12 months). It's easy enough to reproduce, should be easy to spot in a lab with industry test gear, but Sonos may now have chosen not to publicise the results based on their discoveries.

If it turned out that only a hardware modification could restore stability then I can imagine any company involved  being much more cautious about admitting a fault/offering a fix, maybe hoping that another stake holder would back down first. The RMA costs would be considerable, so too would the reputational impact of shipping a hardware fault. 

It's rather ambiguous from Sonos’ response whether they have actually been talking to LG or not before deciding to walk away. There does seem to be evidence of LG trying to mitigate the problem, by at least stabilising HDMI1, but again they could be limited by hardware at this point. I only search for English language forums, there could be LG discussions going on outside my language bubble. Sonos are tiny (by market cap.) compared to LG so may just have the same communication issue with LG that their consumers do. LG have the upper hand here as there's still no evidence offered on this thread of any other eARC device than Beam2 triggering the TV to drop PCM5.1 over eARC.

Seems to me a change from either company would resolve the issue sufficiently. It's a poor response from Sonos whatever the situation:

- they know the cause and won't fix

- they don't know yet so can't fix

- don't want to know and have done nothing for 12 months.

Edit: to be fair, it is also possible that Sonos have investigated and their conclusions are covered by some kind of NDA...

Wish I'd found this thread before buying. LG G3 with Apple TV 4K. Beam 2. PCM 5.1 dropouts.

 It's going back to Amazon this week.

First Sonos purchase, horrible experience. Further to comments already made in this thread...I don't see how I could buy another Sonos product in good conscience given (1) the ramifications of this issue in the future, i.e. products suddenly become unusable following firmware updates and (2) the dismissive manner in which this has apparently been addressed. I loved the sound initially and was even thinking about buying more Sonos products, but nope.

Hi @throwawaybeam2 

I confess I misread your initial post and thought two sources devices were involved, but I see it was just the PS5 and either games or movies on it. We would ideally like to check another source capable of 5.1 PCM, but if you don’t have one that can’t be helped. There was a PS5 update on the 12th of May, so we can’t rule out either that update or our own until we can reproduce the problem, or not, with another source.

I take it you have no issues with built-in TV sources like channels or apps? I don’t believe they would provide 5.1 PCM, so it seems likely, but please check if you haven’t already.

Given that other formats work without issue, including 7.1 PCM, I think we can safely rule out the cable - something that should have occurred to me already. My assumption at this point is that it is a software problem - I’m just not sure who’s, as it could be Sony, LG, Sonos or a weird combo of all three. I’m going to flag this with a colleague to see if we can reproduce this ourselves.

 @ledzep1 

Thanks for responding. I assume you’re on Arc and if so then this could be a Beam 2 only as kikeminchas just came forward with the same issue on the Beam 2.

@kikeminchas

OMG THANK YOU! I didn’t want to to do a full factory reset on my TV (as per Corry P) but I was desperate enough to re-plug/re-register my HDMI devices and do an AV Reset on the TV. Figured this is as close as I can come to refreshing my AV settings without doing a full factory reset. I actually just finished setting up when I saw your response (spoiler - it didn’t work) so it’s truly a welcome surprise. I suppose the CX’s latest firmware update is perfect timing.

From your inputs, we can infer this is probably an issue with the Beam 2 on the 14.10 update. As I was able to use Multichannel PCM 5.1 with no issues before the 14.10 update. Let’s reach out to the Sonos staff and see if they can dig deeper and confirm the issue.

@Corry P 

Hello. As shared above, kikeminchas tested on a PS5 + LG CX + Beam 2 and was easily able to reproduce the Multichannel PCM 5.1 issue. So it’s not an isolated case.

While the sample size is very limited, if we perform a simple process of elimination, it really seems that the Beam 2 on 14.10 is the culprit. kikeminchas tested on a PS5 while I tested not only on a PS5 also a PC. kikeminchas has a CX while I have a C1. Accdg to ledzep1 it works on the Arc and I can confirm that it worked on the Beam 2 prior to the 14.10 update. So all that is left is the Beam 2 running on the 14.10 update.

So again, I would like to ask if Sonos can test for it themselves and confirm if this is indeed an issue or not. This is very easy as in my experience this is reproducible 100% of the time. The engineers don’t even have the wait for very long as the very first dropout occurs with a couple of minutes (and recurs). I have already laid the steps to reproduce the issue. They could test it with a PC which is something they should have on hand.

In my opinion, given that it would literally take 5 minutes for Sonos to test for it, this is the best way to tackle this issue instead of requiring your customer to first perform a factory reset of their TV before moving forward. It is a massive inconvenience, especially if it does not end up solving the issue. I know it’s not exactly what you asked for, but FYI I had just re-plugged/re-registered my HDMI devices and performed an AV Reset on the TV. Figured this is as close as I can come to refreshing my AV settings without actually doing a full factory reset. And issue still remains.

I have an Apple TV-4HD with LG C9 TV and Arc, surrounds & sub and it’s set to default - to output 5.1 multichannel LPCM.

I played the movie ‘6 underground’ from Netflix for 30 minutes or so, just as a test …and that’s all working okay without any audio dropouts.

On the main page I go to param of (input/ouput)

And I got settings screen: 

Hi @ste_ms 

Thanks for updating the thread!

That is baffling - as both formats are McLPCM, they both need the additional bandwidth of eARC, so it seems strange indeed that a cable change would permit 5.1 to work when 7.1 already did.

To be clear I changed the cable between my Apple TV and the LG CX, not the cable to the Beam. I used the stock cable supplied with the PS5 and it has continued to work fine last night and today. The original cable was the Belkin high speed one that Apple sell and recommend for ATV4K. 
 

Also the issue never disappeared for me for me after restarting or changing settings etc but disappeared instantly after changing the cable. However I am continuing to monitor it and will update if the issue comes back.

Ok so, it seems like, hopefully, I managed to fix the problem. I disabled “QuickStart+” in the TV menu, played around back and forth with some of the audio settings for a few minutes (bitstream->pcm and back, passthrough->auto and back, eARC on and off etc. multiple times) then set my PS5 to AV amplifier mode with 5.1 channels and while leaving it on and browsing the web for more info on the problem I noticed that there are no more drops in the sound (the PS5 was on the sound menu for some 15 minutes while it was idle). I found it odd so I went ahead and played a game for several hours, making sure it’s on 5.1 channels mode with LPCM, and there were no more sound drops. I then also noticed that I was not using the Sonos hdmi cable provided with the soundbar but some generic hdmi cable (because the Sonos one was too short). I went ahead and tried replacing it with the Sonos cable just for good measure as I’ve read it’s higher quality. Since then several days have passed and I’ve had no more drops. I don’t know if QuickStart+ was the culprit, or fiddling around with the settings helped, or perhaps it was even the cable, so I know it sounds a little bit like voodoo, but all of these steps together fixed the problem for me, at least so far.

Might be worth a shot for you guys too! Let me know if it helped anyone.

This this!! Thank you! I turned off QuckiStart+ and no more drop out is pcm 5.1 I tested the apple tv nintendo switch and PS5 multiple hours with games movies and tv shows