When you say S1 surrounds, do you mean you’re running the S1 operating system, or do you mean Sonos Ones?

Sonos doesn’t have any control over what the channels are broadcast in...but I’m not sure that’s the issue here.

What I think you’re saying is you’re getting two different audio feeds on the same channel/show on two different TVs. Which suggests something upstream from the Sonos, either the TVs themselves are doing something, or the DTV is, especially if both the Sonos devices are connected via ARC or eARC. if you have one or both connected with an optical cable to the Sonos adapter, there’s other things that might be going on.  

You’ve done what I perceive as the right settings, but if by DTV you mean DirecTV, I’d suggest setting the DirecTV box to Dolby Digital, not Auto. Having been a customer of their for about 25 years (as a guess), I have very little confidence in the hardware they provide. 

The Sonos HT devices will only play the audio sent to it at whatever ‘given’ volume via the TV - they are speakers after all and don’t alter their own volume level, but simply play the audio, as instructed.

To change anything, like the codec/volume you need to look upstream to the TV, or source device and set the type of audio/volume levels there - it’s really out of Sonos hands to do that.

So that said, I would change the TV, so it does not ‘pass-through’ the audio, but instead processes the audio into whatever codec the TV supports - so if there is an option to select Dolby 2.0 audio, or PCM stereo audio (if that’s your preference) then select that for the TV sound-out, but note, you will likely want to switch it back when listening to a surround sound movie or show, as otherwise you won’t get the audio output from all channels to your rear speakers etc.

I have a TV with no soundbar in a campervan and the volume-level changes on that when switching between standard and HD channels, so it’s definitely an issue with the source, rather than the speakers.

Surounds are Sonos Ones, Sonos App is S2. I mean that on the LG TV when changing TV stations, I get vastly different volumes. By DTV I mean that in the LG TV Setup / Sound / Additional Setting, the DTV Audio Setting is set to Auto - other options in this setting are MPEG, Dolby Digital, Dolby Digital Plus, & HE-AAC. All blogs I found suggest Auto is the best option for this setting. I have tried changing this setting and it has no effect on what the Sonos App reports in About My System or in volume levels.

The second Sony TV has no issue with volume levels using similar Sonos equipment (albeit ARC instead of Beam2),

@GaryTur,
Maybe speak to LG Support and see if they can suggest anything to assist, as the ball appears to be in their court.

Hello, i have the same experience with different loudness between channel. LG oled cx3lb. If I disconnect arc, it open possibility to sync loudness on tv and all channels goes more less same. Any advice please?

I’d suggest the post before yours might be the best starting place?

Didnot mentioned, that I have Sonos arc 2 years and it was ok till this fall. 

The Sonos has no idea about what ‘channel’ is being sent to it, either across optical or ARC. It just plays what it is told to play. If there’s variation in volume levels, it is originating upstream from the Sonos. 

Same problem here with tv channels.Anyone find a solution?

I would get in touch with your TV channels provider and see if they can fix it, as the Sonos speaker is not likely changing the volume level, which you should be able to see in the Sonos App, unless it’s something that your TV is perhaps doing to the audio?

On the SONOS Now Playing screen, check the audio stream format. Different audio formats might be perceived to play at different levels. For example a simple stereo format might be highly compressed and seem louder compared to a less compressed surround or high definition format.

Hdmi is on passthrough ,so the tv doesn't impact the sound.The problem is when i change the channel from one with pcm stereo  to another whith dolby sound the difference in volume is huge.Is so big that i must to lower the volume from 75 to 25 so the volume output by sonos to be the same.I don't think this is normal behavior and Ziki78 mention that this problem wasn't till this fall...i bough the Arc recently and this is the reason i don't know more details about previous firmware .So,in conclusion,i can't watch tv at night because that diference in sound volume is huge....effectively i wake the neighbours if the sound is set to 75 and the next channel have dolby sound or i can watch any program using volume set to 25 and the channels with pcm stereo sound are inaudible.

Hi. Anyone find a solution to this.

I have the same problem with a Sony A90J connected to cable set top box and Sonos arc with Sub Mini and Era 100’s as rears. All the items are new, set up about a week ago, and when I first connected everything it worked fine. Either Dolby digital 5.1 on some channels and dolby stereo 2.0 on some others and the sound level was the same on all. Since about 3 days ago, there is a major difference in sound volume between different tv stations. Those that showed DD 5.1 before still show DD 5.1 but those that showed DD 2.0 before now come up as Stereo PCM and the the volume is significantly lower. I tried unplugging everything , waiting a few minutes and reinstalling everything but that did not help…..same problem. All sound output settings on tv ( earc: Auto; output: Dolby Digital Plus ; Pass through mode: Auto are the same as when it was working properly. Same for the set top box which is a Huawei Q22 ,from Altibox provider in Norway. Settings on set top box are Audio Output: Dolby Digital 

Any help or solutions are greatly appreciated.