major problem with Sonos Arc Ultra - Sonos doesn't let switch to other speakers from TV menu

Sonos does seem check in with the TV and re-establish the connection via CEC more compared to other soundbar manufacturers. As Sonos also seems to adhere to the HDMI-CEC spec (as you must have read in the threads you link  to), this might not be identified as a problem. Since Sonos is aimed at less tech savvy (but affluent) consumers this might even be a feature, not a fault. Would it not be possible to turn CEC off temporarily?

The Sonos’ answer to the fact you cannot connect a headphone reliably when you do not turn off CEC on your TV is to use the Sonos Ace’s TV Audio Swap feature.

As is detailed in the other threads the sound output routing is determined by the TV and not the speaker device, in this case Sonos. All Sonos does is let the source, controlling, device (your LG TV) know it is there and ready to use. The TV decides to use it, or not. Sonos is not 'stealing' the sound - just processing what it is given by the source.

This is all as per the CEC specification. Your issue would seem to be with, in this case, LG WebOS and not Sonos... maybe raise it with them?

Would a CEC blocker on the eARC line stop this?

What else would it break?

Since every TV I've used has just worked I'm clueless here.

I just switch off simplink on my LG TV and am then able to switch to other speakers/outputs, or audio inputs - i thought that’s how most TV’s work these days with the (enhanced) Audio Return Channel enabled alongside CEC. On a Samsung TV you simply switch off AnyNet+, just as another example.

If switching off these things becomes problematic- maybe consider using the TV’s Optical output instead to the soundbar, via the Sonos Optical to HDMI adapter. It’s slightly restrictive with some codecs being unavailable, but it may help simplify the switching to other speakers etc.

Another option would be just to power down the soundbar when not required, rather than changing to using an optical connection which restricts available audio formats.

The replies here are making ridiculous outlandish excuses to clearly a problem - that defies common sense, logic and how other soundbars operate.  

Moreover, even turning SIMPLINK (HDMI-CEC) in LG TV menu DOES NOT work properly.  The setting toggles back!! if you try to turn it off, the same way the sound gets restored.  So other than physically disconnecting the HDMI cable or power cable to the soundbar there is no way to shut down sound output to Sonos.  Completely ridiculous. 

Must be the way LG have implemented CEC on that particular TV model - I don’t have that issue with my LG C9 OLED TV, it simply disables and stays that way. Maybe see what LG Support suggest in this instance - there might be something in the TV’s hidden service menu they can (perhaps) adjust for you, or maybe fix it with a TV firmware update. 

The CEC spec is not very tight and each manufacturer uses its own interpretation. If manufacturer ‘A’ is causing issues for one or more other manufacturers they may make accommodations. Unfortunately, at a later date ‘A’ might make some changes that breaks these accommodations.

A CEC blocker will probably help the sound and video issues at the cost of some automation convenience for the user. A user remote will need to be configured to send IR Volume commands to the SONOS soundbar.

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Also, using a BT headset requires registration in the LG menu. In addition to disabling CEC.

Not trying to promote Sonos sales but investing in the Sonos Ace may be a good investment to use Audio Swap.

Personally, I don’t see the logic to spend $1000_USD or the equivalent in foreign currency for an Arc Ultra to swap back to the TV’s internal speakers🤔. I’m sure someone will post a use case… so each to their own. Once again C’est la vie.

Just to add a OP's and ​@AjTrek1 observations. I have a 2025 LG OLED55C5 evo with my Arc Ultra and I see the same issue as reported but, as also suggested, this can be overcome by:

* On the LG navigate to the Sound > Advanced Settings and turn off eArc Support

* On the LG navigate to the General > External Devices > HDMI Settings

toggling SIMPLINK (HDMI- CEC) will then switch between the TV and Ace Ultra speakers. However you loose the advantage of eArc functionality.

As posted previously my understanding is that this is CEC compliant and the issue is with WebOS or hardware implementation on the LG C5. This seems to be supported by other contributors experiences also.

Personally I do not see it as a problem, the internal LG speakers although fair are rubbish compared with the Arc...

And once again.  This problem affects all brands of TV’s not just LG.  HDMI CEC setting cannot be turned off reliably.  Other brands of soundbars are not plagued by this problem.  

And finally, it is my desire and business how and what way to listen to what output at what time.   LG’s speakers on one set might not be good, but other TV speakers might be great.  There are also other speakers or headphones that might be required to be connected; and I use headphones regularly at night.

In the case of LG, even their private listening functionality, through the LG ThinQ app, that allows to route the sound to the phone through WiFI is not working as well, exhibiting the same behavior when Sonos is connected.  

1. One shouldn’t have to jump through 10 menus to turn off anything, because of bug or limitation.  After turning off HDMI CEC, you are not just loosing the control functionality with Sonos, you will not be able to play anything through Sonos at all, until HDMI CEC is turned on (assuming that you can turn it on/off).
2. Sonos either needs to modify the way the way they issue and receive control commands from the TV and/or add compatibility setting in the app to prevent this from happening and/or add a soft power down to the soundbar from their app to allow the TV’s to route sound to other audio outputs.

Lets agree to disagree but I feel that Sonos is adhering to the eArc/CEC spec. My experience is that it is not CEC per'se but eArc that, from a user PoV, is 'causing' the automatic selection of the external, in this case Arc Ultra, speakers. Again this is not in conflict with the protocol specs as I understand them…

Like a lot of things in this software based technological world a 'standard' tends to be open to interpretation - VHS vs. Betamax was much easier 😂🤓😋

I am not a Sonos apologist but just because Sonos interprets the specs, I believe, correctly does not mean they are in the wrong. Other manufacturers, older, products behave differently, for whatever reason.

Don't get me wrong, I am no expert, but In this case I think the 'blame' probably lies elsewhere.

Thinking all consumer electronics behave alike because they follow the CEC “standard” is like saying all gumbo recipes in New Orleans are alike because they follow the standard of a roux, the trinity, and Okra or File powder.  

​@dintis I must say the complaint that CEC cannot be turned off reliably seems to be an LG problem. I do not remember reading that about other manufacturer's  TV’s.

Some TV’s disable advanced audio distribution if CEC is disabled. In my experience a CEC blocker causes fewer issues. In any case, after disabling or blocking CEC, more manual operator action will be required.

I tested Klipsch Flexus Core 300 with my LG C5 TV and the described problem does not exist there at all.  Everything works as expected.   So yes, this is a Sonos problem.  

I don’t have any knowledge of HDMI CEC protocol and would need to look at the captured traffic, but it could be that Sonos is constantly trying to assert itself as the active playback device or constantly broadcasts its availability or being on and/or ignores other commands from the TV to give up the control.  As a result of this, the TV momentarily switches to another output but then yet another message from Sonos arrives and the TV routes the sound again to Sonos.

These are just my guesses.

You can’t simply try another soundbar and determine it’s a “Sonos problem”.  I have two TV’s, a Samsung and a Toshiba, both have Sonos soundbars.  The Samsung needs CEC shut off in order to use the TV speakers or Bluetooth, the Toshiba switches back and forth no problem.  Can I say that it must be a “Samsung problem”?  Of course not.  Rather than that, I say it’s a CEC problem, because I know CEC is about as “unstandard” as a standard gets.

Could you please provide the models of the TVs you tried it on (Samsung and Toshiba)?  So that Sonos developers could potentially address the problem that is “not a problem”?

I don’t consider this a Sonos problem, and I’ve already alerted Samsung.  To tell the truth, I only tried to switch due to curiosity after the complaints here.  Personally, I cannot for the life of me understand why one would spend thousands on a Home Theater system and then need to switch back  to the tinny TV speakers that sound like crap.  As for Bluetooth, the very few times I need to use headphones, I use my Sonos Ace.  

So what are the Samsung and Toshiba tv exact models? 

Samsung - 83” Class S90C OLED Smart Tizen TV (2023)

Toshiba - 55" Class C350 Series LED 4K UHD Smart Fire TV

Note to Sonos staff:  I’m only listing these because it was requested.  I expect you to do nothing with this information, because I know the CEC functionality to switch between audio devices resides in the TV, not the individual audio device.  I also find it quite logical that a TV automatically defaults to the best sound available.