If you notice a difference it’s entirely psychological. As it says on that option it’s a “setting to override the preset for Line-In”.

https://support.sonos.com/en-gb/article/adjust-line-in-audio-compression

I’ve got a similar setup, but I’m not seeing the same issue - I also haven’t seen anyone else complaining about this type of issue either, might it be your TV perhaps (any recent firmware update), or have you set a volume-limit in the Arc’s room settings?

What make/model of TV is the Arc attached to?

It maybe worth also changing the HDMI cable between the TV and Arc to see if that makes any difference.

That’s a data compression setting for Line-In, not for dynamic range compression. They’re totally different concepts.

I’m not having any of the issues mentioned, but just to add my Sonos HT rooms have all had Trueplay in situ probably for several Sonos updates now and the Sub (gen3), bonded to the Arc & Surrounds, sounds fine to my ears. I have the Sub volume and Bass EQ set at zero - if I increase the Bass to +2 and the Sub level to +7, then it’s far too much for how I like to listen to music/TV audio - the Treble also seems fine to me at zero. I’ve not noticed any sibilance, for example.

I can’t say I’ve noticed any recent changes at all. I do find it difficult to comment on volume levels because in my own experience, audio sources, music and TV, can vary so much by channel/show/movie/codec/source-device etc; but generally speaking, the TV volume-level in the App usually sits somewhere between 35% and 45% - We do use ‘night mode’ when watching the TV in the evenings so as not to disturb people sleeping, or neighbours, - the drop in Bass is very noticeable when that feature is enabled. I rarely use ‘speech enhancement’ as the Wife & I tend to prefer that feature disabled, the speech audio from our LG TV/Arc seems to be quite natural and clear enough without it, again though this can vary by source, but generally, it’s fine.

That’s the big problem with Sonos…they are constantly changing sound or volume. You never know what you’re going to get with these freaking to many updates…

Details? Which speaker(s)? If there’s a Sub involved is it actually working? Have you tried powering the affected units off for 30 seconds then on again?

Sonos has, to my knowledge, only changed the sound profile on the Arc a couple of years ago. There’s only a couple of mentions of people noticing a change now, so it is not clearat this moment if there really has been an intended change.

I trust Sonos the updates I receive are necessary, either for computer safety reasons, stability of the service or for adding new features. There have been instances where Sonos has been pushed take away features too, but that’s inherently linked to changing circumstances. So, based on this trust (and my lack of knowledge about Sonos’ processes) I cannot say there are too many updates.

Probably best to get word from Sonos about this.  My guess would be that a change was made to fix a minor issue for a small portion of customers, but had unintended consequences for a different set of customers.  Has anyone called Sonos support on this, had a diagnostic looked at?

Where is that ‘compression’ setting in the software, I can’t see where you mean?

Could you perhaps be mistaken about the dynamic range compression here @Tulo, in a similar way that you were clearly mistaken about the line-in data compression changing your streaming music audio, as that Sonos App setting has no effect on streaming audio. That feature applies only to line-in audio?

Have you checked all your Sonos App ‘room’ settings and ensured you, or someone else in your household, have not enabled ‘night mode’ when listening to TV audio, or reduced the volume level of your Sub, or changed your room EQ whilst listening to music audio etc?

The Arc, surrounds (Era-300s) and Sub (gen3) setup here with an LG C9 TV sounds fine to my ears and to the Wife’s ears too - We’ve not noticed any sort of significant sound change by the recent S2 firmware updates. 

Our Sub Bass output when watching the movie John Wick 4, for example, still sounds very punchy, as do our streaming music services (Amazon Music HD/UltraHD). Certainly the start of the John Wick movie is more than enough to have our neighbours complaining, even at a 35% volume level with ALL settings set to default... it still rattles the glasses in a cabinet we have next door in our dining room.

15.9 firmware has restored the dynamic range thanks, Sonos

If you and any others in your household cannot tell the difference in audio output when the Sub is enabled/disabled, whilst playing a variety of music sources, or surround sound movies with DD 5.1 codecs etc; then you really ought to submit a Sonos diagnostic report and contact Sonos Customer Care as there is quite clearly something wrong in that instance. I have no issue hearing a difference when toggling the Sub ON/OFF and my daughter/son-in-law at their Home say they can hear a clear difference too and both are happy their SUB is working correctly with their Arc/Sony TV. 

Noticed that the sound on mine had harsh treble again so I turned off truplay and sound went back to normal 

with truplay on I had to turn treble to -5 and turn bass up 

tried on my arc movie only system and my 2 5s both have subs attached 

so if you have truplay turned on turn it off see if the rich bass returns

i think you are wrong the make a big change in the sound profile my sonos rear one are sound different after the update.

Turned off Trueplay and volume has improved, not sure if it's as loud as before yet. 

Sounds much better without Trueplay currently, definitely wasn't the case before so seems like my Trueplay has gone weird with the update (in comparison it's quite treble heavy and harsh). Strange. Don't currently have an Apple device to redo Trueplay.

Yeah, I noticed a big drop in bass on my dual sub setup. Trueplayed and not trueplayed.

i know sonos a lot of year. the 15.8 update is the worst update ever.

connect issue to my tv 

the change the sound profile for worse low bass low volume the rear speaker behave differently and more worse then before.

the right thing is let customers to go back to 15.7 and fix 15.8 frimware. 

I have redone truplay and it went worse also redid it using ios16 on my iPad it is still bad

for now going to leave truplay off it sounds better 

I get the sense that there is also a push in lowmids going on. 

It's like they confused teh big sub with the minisub in the soundproflie. 

Sub GEN three doesn’t have the punchy base like it used to It still sounds good but it’s lost some output I have a lot invested in Sonos and I’ve been recommending it but now that they’ve started doing this stuff what sounded really good now sounds mediocre

To my knowledge, Sonos has made zero adjustments to the sound profile of their speakers with 15.8 or 15.8.1. It makes me wonder if there’s a local issue. 

I know it’s not a local issue it’s an overseas issue. These are made in China with cheaper parts and I think they’ve done it so you’re not overdriving the speakers to protect them it could be a warranty problem that they’ve lowered the output, slight bit hoping that most people won’t notice?

Right. That’s why there are thousands of people complaining here in the forums about the update. You may be projecting your prejudices a bit much. 

I'm not sure how much my sub specifically has been affected but overall volume is way down. Currently having to watch films at about 60 as opposed to 35 on the last firmware. I put it up to 90 and it wasn't even that loud - that would be unbearable previously. Seems like the same issue from a few firmwares ago - anyone else with this issue?

I've got an Arc, 2 x One SL surrounds and a gen 3 sub.

What Sonos software engineers have done is lower the audio compression threshold like Bose does and it’s really quite noticeable and it really affects streaming music and it doesn’t matter if it’s Apple or Amazon what used to rattle my dishes upstairs no longer does that’s what’s changed. In the Sonos system app. There is a setting audio compression. I always kept mine uncompressed and made no difference it’s been changed in the firmware