Contributor I

Question

Sonos Arc Ultra + Sub Gen 4 – Severe HDMI eARC Sound Issues with Hisense and LG TVs

Forum|Forum|13 hours ago
October 12, 2026
20 replies
141 views

Hi everyone,

I purchased a Sonos Arc Ultra and Sub (Gen 4) last month and initially connected them to our one-year-old Hisense 55U7NQTUK TV.

My current setup:

- Soundbar: Sonos Arc Ultra

- Subwoofer: Sonos Sub (Gen 4), connected wirelessly to the Arc Ultra

- Original TV: Hisense 55U7NQTUK

- New TV: LG QNED86B (purchased on 10th October)

- HDMI connection: Sonos Arc Ultra connected directly to the LG TV's HDMI eARC port using the original HDMI cable supplied by Sonos

- Audio connection: HDMI eARC, with no additional devices or adapters between the soundbar and TV

With the Hisense TV, I experienced two frustrating issues. Firstly, the sound would randomly cut out completely while watching TV, forcing me to switch the audio output to the TV speakers and then back to Sonos to restore the sound. Secondly, whenever I switched the TV on, the volume would occasionally jump to full blast.

After researching the issue online, I discovered that it could be related to an HDMI eARC/CEC handshake problem between the TV and the Sonos system.

Hoping to resolve this, I purchased a brand-new LG QNED86B on the 10th of October. Unfortunately, the situation has become even worse, and I can now barely use my Sonos system to watch TV at all.

It's incredibly frustrating, especially considering the significant investment in the Sonos Arc Ultra, Sub (Gen 4), and now a brand-new television purchased specifically in the hope of fixing this issue.

Has anyone experienced similar problems with the Sonos Arc Ultra, particularly when connected to an LG TV? Could this be an HDMI eARC, HDMI-CEC (Simplink), firmware, or Sonos compatibility issue?

I'd really appreciate any advice, troubleshooting suggestions, or a permanent solution, as I simply want to enjoy my Sonos system without constantly dealing with these problems.

Many thanks in advance for your help!

Stanley_4

Grand Maestro

The first thing I would do is get the problem to occur and submit a diagnostic, sooner is better, over 10 minutes is iffy. If you can catch multiple problems submit a diagnkstic for each one, note the diag number and issue. When you have time contact Sonos support and have them examine the diagnostics.

You can search here for previous reports of LG issues too.

M

ManxguruAuthor

Contributor I

Thank you Stanley, I've shared the diagnose number

Stanley_4

Grand Maestro

You can't share the diagnostic number here, it upsets Sonos legal.

You have to contact support (they don't visit here) to get the diagnostic evaluated.

M

ManxguruAuthor

Contributor I

Diagnose no: ******** sent on 11th of October at 19:49

Moderator Note: Recorded and removed Diagnostics number. Modified in accordance with the Community Code of Conduct.

Flying monkey

Lyricist III

I would try turning off the CEC on the connected devices, I swapped out my Beam gen1 for a Beam ultra and had random drops outs, turned off all the CEC on the devices and it has stopped.

M

ManxguruAuthor

Contributor I

Thank you very much for your suggestion. That's really interesting, especially as you've experienced similar audio dropouts and managed to resolve them.

I'll certainly give this a try. Just to clarify, are you suggesting that I disable HDMI-CEC on all other connected devices but leave Simplink (HDMI-CEC) enabled on the LG TV for the Sonos Arc Ultra to work through eARC?

I really appreciate your help!

Flying monkey

Lyricist III

Yes you need to leave it on for the Sonos, but disable it on your other devices.

M

ManxguruAuthor

Contributor I

Thank you for confirming. I'll give that a try and see whether it resolves the issue. Really appreciate you taking the time to help!

buzz

Grand Maestro

Individually disabling specific CEC’s using device options is not always practical. Plus, a device update might re-enable its CEC long after you’ve forgotten this trick or mom and dad never knew or understood what you’ve done. A CEC blocker is usually a better, more permanent approach.

Disabling CEC will have some side effects, such as disabling auto power-up and input selection for the CEC disabled devices. The most awkward side effect may be blocking Volume commands from passing between devices over CEC. I say “may” because you can usually use direct IR commands that are still available on most device remote controls. I’m sure many users will not notice the difference.

I can imagine that IR commands will become obsolete at some point because it will be cheaper for the manufacturers to eliminate IR and use Bluetooth in their remotes. Then including remotes in the package will be optional, forcing the use of phones or an optional remote purchase.

M

ManxguruAuthor

Contributor I

Thank you, Buzz. That's very useful information, and I wasn't aware that HDMI CEC blockers existed.

I have an Amazon Fire TV Stick connected to my LG QNED86B, alongside the Sonos Arc Ultra through HDMI eARC.

I'll first try disabling HDMI-CEC on the Fire Stick to see whether that resolves the sound dropouts and sudden volume increases.

If it works, I'll certainly consider a CEC blocker as a more permanent solution.

Just to confirm, would the blocker go between the Fire Stick and the LG TV, leaving the Sonos HDMI eARC connection untouched?

Really appreciate your advice!

MoPac

Headliner III

Until your problem is solved I would advise setting a Volume limit for the Arc Ultra Room.

M

ManxguruAuthor

Contributor I

Thank you MoPac, I tried that but that made it worse unfortunately

buzz

Grand Maestro

You’ll need to experiment with the CEC blocker location(s), Set-top boxes sometimes think that they own the network and isolating them can be a great problem solver.

One of my favorite glitches is the middle of the night cable box update. As a user convenience the box will power ON as the update finishes. CEC will then assume that the user wants to watch TV … . Another glitch can occur as you shut down for the night, First you turn OFF the TV, then the box you were playing. At this point you leave the room. Meanwhile, CEC is mulling things over and notices that the cable box is still ON (cable boxes usually don’t power down) — obviously you must want to watch TV. CEC will restart the TV, but you don’t notice because there is a startup delay and you have already left the room. In the morning you discover that the cat must have wanted to watch TV sometime during the night.

Edit: By the way, if you have the tool, skill, and confidence, just remove pin 13 from the HDMI cable. (Good luck!) Don’t first attempt this on your favorite cable. Plus, if you change your mind, the cable must be replaced. A CEC blocker can simply be removed.

M

ManxguruAuthor

Contributor I

Thank you, Buzz. That's a really interesting explanation, and I can see how HDMI-CEC commands from other connected devices could potentially cause these problems.

I have an Amazon Fire TV Stick connected to my LG TV, so I'll first try disconnecting it completely and testing the Sonos Arc Ultra on its own.

If that resolves the issue, I'll reconnect the Fire Stick with HDMI-CEC disabled and see how it behaves.

I've also updated the Sonos software and ordered a replacement HDMI cable, so hopefully we're getting closer to identifying the cause.

Really appreciate your advice and taking the time to explain everything!

AjTrek1

FWIW…

I have four (4) LG’s including one with Nano Tech as the QNed mentioned by the OP. All except one are connected to Arc Ultra’s the other to a Beam Ultra. All use HDMI eArc with CEC enabled and have AppleTV 4K connection via HDMI. Cable broadcast via HDMI is provided by Comcast. My ISP is GFiber. No Audio issues.

My recommendation is to keep the onboard programing via LG Magic Remote simple. Only agree to T&C’s and Privacy agreements. Make sure 3rd party remotes (AppleTV/cable) work with Sonos volume. I don’t program LG Magic remotes to control any other devices. Check for updates for all products. Setup Sonos first and 3rd party devcies later.

Together Everyone Achieves More = T.E.A.M.

M

ManxguruAuthor

Contributor I

Thank you very much for sharing your experience. It's reassuring to hear that you're running several LG TVs with Sonos Arc Ultra soundbars without any issues.

I've already updated my Sonos software, and I'll check that the LG TV and Amazon Fire Stick are fully updated as well.

I'll also try disconnecting the Fire Stick and setting up the Sonos on its own first, as you've suggested.

One thing I'm particularly concerned about is the volume suddenly jumping to maximum when switching the TV on, alongside the random audio dropouts. Have you ever experienced anything similar with your LG and Sonos setup?

Really appreciate your advice!

AjTrek1

No loud volume upon normal startup. Although it could happen if you were playing a source that required the volume to be higher than normal such as after a music stream or AppleTV. Other than that no other instances.

Together Everyone Achieves More = T.E.A.M.

MoPac

Headliner III

I have a Beam 2 connected to a newer LG TV. Also there is a Fire Stick connected to the same TV. I did nothing to the default settings of the LG. No issues with connection or volume changes.

This is likely not related but recently I had an issue with one of my rooms suddenly at full volume. It turned out to be the third party app Sonify. Apparently that app along with other similar apps activate the iPhone volume buttons. I was not aware of this until I think the iPhone volume got cranked up when I grabbed the phone with my clumsy hands while Sonlfy was open & nothing was playing. No longer using Sonify.

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