There is currently no center volume control, but you can perhaps try using, TruePlay tuning, ‘speech enhancement’ and/or ‘night mode’ features, in conjunction with both the EQ and the ‘TV level’ slider bar in surround audio in the HT room settings in "Settings/System”.

The ‘night mode’ and ‘speech enhancement’ buttons are located on the App’s ‘Now Playing’ screen.

Are you getting 5.1 audio playing out of the Arc?

Playbar does not offer this feature either afaik it came out in 2013. Seems unlikely this will be added IMO. 

Frequently, but not always, folks who complain about this are not having their TV (or devices connected to the TV) sending a Dolby Digital signal through to the Sonos device, so as GS suggests, it’s worth checking before then moving back to Ken’s post. 

Just like every other device I’ve seen out there, Sonos doesn’t do a “convert from Stereo to 5.1” very effectively, so it really needs to be receiving the correct signal. Which can be an issue with the TV, or things feeding the TV a signal. 

Yes

Thanks been trying that as well but still end up adjusting the overall volume for loud and quiet scenes

The Night Sound feature does a really good job lowering the dynamic range of the audio making quiet sounds louder and louder sounds more quiet. I’m surprised it isn’t helping. Have you performed Trueplay tuning?

Thanks I retuned it and put the night sound on and it’s a lot better