Dolby Digital 5.1 voice track coming from rear surround speaker

In the past few weeks the vocal track of Dolby Digital 5.1 sound has been only coming out (loudly) of the left rear surround speaker of a Sonos Arc system. No voices come from the Sonos Arc, but it sounds like surround speaker sounds are coming from the Arc. So shows in DD 5.1 are basically unlistenable.


My system: 1) Sonos Arc/Sub/2 Sonos One surrounds, 2) LG CX 77 TV, 3) Apple TV 4K 3rd gen


I stumbled upon a fix, which is to toggle eARC off and back on again on the LG CX TV. After than sound comes from the Arc, but eventually this has be redone (see below). 


Why is this happening and is there a better fix? This is a new problem that started a few weeks ago.


Further details:



  • My fix of toggling eARC on/off works, but when you change Apple TV’s audio format to “Auto, Atmos Available” and back to “DD 5.1” then voice starts coming out the left rear surround speaker again. It’s a pain to have to keep doing this, but better than having to listen to lower-quality multichannel PCM 5.1 instead of DD 5.1


  • Rebooting Apple TV doesn't help. Removing/reinstalling surround speakers in Sonos doesn't help.


Apple TV 4K (3rd generation)

Posted on Dec 24, 2023 10:56 AM

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5 replies

Dec 24, 2023 11:21 AM in response to tpntpn

Is the LG set for ‘untouched’ audio passthrough? Because it seems that something changes the signal in there.

Try contacting LG Support, see what they have to say about your issue.


… when you set it to “Auto, Atmos Available” you get Multichannel PCM 5.1 which sounds bad.

It should sound exactly the same, as PCM 5.1 can be losslessly decoded from DD 5.1 or AAC 5.1 or other 5.1 inputs. There is nothing inherently better about DD 5.1. On the contrary, DD 5.1 might be less exact(but probably not audible), for being lossy compressed when re-encoded if needed to force the format .

The only way for an audible difference is if your equipment does post-processing one way on one format, but not or different on the other format. Such conditional treatment shouldn’t happen on good equipment.


Rebooting Apple TV doesn't help. Removing/reinstalling surround speakers in Sonos doesn't help.

Does rebooting the LG TV help? Have you checked for newer LG TV system software/firmware?

Dec 24, 2023 11:58 AM in response to Urquhart1244

Is the LG set for ‘untouched’ audio passthrough? Because it seems that something changes the signal in there.


yes, LG is set to passthrough


It should sound exactly the same, as PCM 5.1 can be losslessly decoded from DD 5.1 or AAC 5.1 or other 5.1 inputs. There is nothing inherently better about DD 5.1. On the contrary, DD 5.1 might be less exact(but probably not audible), for being lossy compressed when re-encoded if needed to force the format .
The only way for an audible difference is if your equipment does post-processing one way on one format, but not or different on the other format. Such conditional treatment shouldn’t happen on good equipment.


On my Sonos Arc system, for shows that have a DD 5.1 soundtrack, there is a noticeable drop in quality for Multichannel PCM 5.1 vs. DD 5.1. It isn't subtle, it's clear and obvious. Voice, music, everything is much clearer and better defined w/ DD 5.1. Multichannel PCM 5.1 sounds thin and tinny in comparison. With Sonos, Apple, and LG in the loop it isn't clear who is the cause.


Does rebooting the LG TV help? Have you checked for newer LG TV system software/firmware?


LG firmware is up today. Haven't rebooted LG TV yet because understanding is that it involves unplugging the TV. Not easy with my wall-mount, so I have to flip the circuit breaker. Will try soon.

Dec 24, 2023 1:09 PM in response to Urquhart1244

Does rebooting the LG TV help?


Nope, flipped circuit breaker for a min, TV restarted, and can still reproduce audio problem.


Can reproduce audio problem each time by Apple TV Settings > Video and Audio > Audio Format > Change Format Off (Auto, Atmos Available) and then change it to Change Format On (DD 5.1). Vocal track then comes from the Sonos One left rear surround speaker. Toggling LG CX TV eARC off/on corrects the audio problem.  

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Dolby Digital 5.1 voice track coming from rear surround speaker

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