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Answered

Problem with Beam Gen 1 and LG OLED42C4

  • June 4, 2025
  • 6 replies
  • 201 views
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Beam Gen 1 connected to HDMI2, eARC port.
2x One SLs setup as surround
Using official sonos HDMI cable
WIFI connection to Beam
Ethernet cable to TV

this setup worked fine with 43” LG for last 5 years
upgraded this week to a 42” OLED LG C4, fresh out the box.

No DVD, Bluray or STB. Streaming apps only.

 

Soundbar receives Dolby 5.1 from onboard Apps - Netflix, Amazon Prime, Rakouten, Now TV etc. as expected. Sounds good… except every second appears a lag or drop in volume. 

Happens no matter what the streaming app being used.


Tried all the Sound Format settings, eARC on / off, CEC SIMPLINK on / off, changes to Auto / Passthru / PCM, changes to digital sound format MPEG/DD5.1/DD5.1+/HD ACC something / Auto

Problem only goes away when output format is set to PCM. But then this is only Stereo 2.0, losing the surround etc.

Haven’t tried Optical yet, because I can’t find the Beam adaptor. May need to order one onlne.

Tried turning everything off 2 mins, on again [at the wall, not standby].

 

Best answer by Airgetlam

Worth the try of another cable, although one that requires nibbling down to fit doesn’t sound ideal to me as a test case…but if you’re currently using the Sonos cable, I’ve not seen any instances here of those failing. Which isn’t saying it’s not possible, just a very low chance.

I really think it’s the TV not sending the appropriate signal (being removed/not there). I’d be very tempted to do four things, in addition to that cable testing. First and second, I’d be checking both the TV and Sonos for any software/firmware updates, and apply them as necessary, if they’re found. Third and fourth, I’d reboot both devices, starting with the TV and moving on to the Sonos, by unplugging them from the wall for two minutes. This will force them to reload their respective OS, and after booting up, force a new handshake of CEC across the HDMI cable.

The challenge (which may not be one for you) is the optical adapter restricts you to Dolby Digital. No Atmos at all. And there’s no backwards connection to the TV set, as optical only carries data one way.

Finally, and I guess fifth (and last), I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

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6 replies

Airgetlam
  • Airgetlam
  • 44829 replies
  • June 4, 2025

Have you reported this to LG? It seems like the TV is struggling, for unknown reasons, to send an appropriate signal to the Sonos, via CEC. I’m assuming you’ve updated the TV’s firmware. 

Bruce
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  • drgaff
  • Author
  • Contributor I
  • 3 replies
  • June 4, 2025

Had set auto-update on the TV, but it was a version or so behind.

Updated firmware to the latest tonight, afterwards, powered off, waited 2 mins, retested.

Still same issue. Will contact LG and see what they say.

D
  • drgaff
  • Author
  • Contributor I
  • 3 replies
  • June 6, 2025

Been onto LG, they say “Cable or compatibility problem.”

Have tried a different cable, had to whittle down the insulation around it, as the Beam one is recessed in a round indent and my fatter cable didnt quite fit snug enough. No sound at all via that - which surprised me, as the HDMI cable works afaik. Reverted to Sonos HDMI for now.

Have ordered a sonos Optical->HDMI adaptor. 

Really don’t want to have to upgrade the soundbar, the only other Sonos unit that will visually go is a Beam gen 2 - the Arc is too big for the LG 42”. And I don’t want to break off the Sonos ecosystem as its part of the whole house by now.

Airgetlam
  • Airgetlam
  • 44829 replies
  • Answer
  • June 6, 2025

Worth the try of another cable, although one that requires nibbling down to fit doesn’t sound ideal to me as a test case…but if you’re currently using the Sonos cable, I’ve not seen any instances here of those failing. Which isn’t saying it’s not possible, just a very low chance.

I really think it’s the TV not sending the appropriate signal (being removed/not there). I’d be very tempted to do four things, in addition to that cable testing. First and second, I’d be checking both the TV and Sonos for any software/firmware updates, and apply them as necessary, if they’re found. Third and fourth, I’d reboot both devices, starting with the TV and moving on to the Sonos, by unplugging them from the wall for two minutes. This will force them to reload their respective OS, and after booting up, force a new handshake of CEC across the HDMI cable.

The challenge (which may not be one for you) is the optical adapter restricts you to Dolby Digital. No Atmos at all. And there’s no backwards connection to the TV set, as optical only carries data one way.

Finally, and I guess fifth (and last), I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Bruce
D
  • drgaff
  • Author
  • Contributor I
  • 3 replies
  • June 9, 2025

Optical adaptor arrived. Sound is fine thru that.

Optical out isnt presenting the same issues as the eARC socket. 

Initial loss of volume adjustment, but remote can be setup via the TV for the soundbar, so everything back as it should be.

 

Airgetlam
  • Airgetlam
  • 44829 replies
  • June 9, 2025

Which suggests some sort of issue, unknown, from the ARC signal or connection. I’d still want to go with that fifth option above. 

Bruce
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