What type of audio are you getting from the Arc? Have you performed Trueplay tuning? If you are seated close to the surround speakers, you might adjust the Surround Audio TV Level setting lower so it will be easier to hear the audio from the Arc.

Unfortunately I don't have any iOS products to use trueplay. I think that would be best way to optimize. I didn't try turning down the surround yet that's a good idea. thx

You haven’t responded to the first question. Most frequently, people with complaints about hearing dialog properly come from people who are sending only a stereo signal to their system, which doesn’t have a ‘center’ channel. This can be an issue with the TV, but more often is an issue with the device feeding the TV.

Find a friend or relative with an iOS device and ask them if you can borrow it for 15 minutes. You only need to perform Trueplay tuning once.

Here is a list of iOS devices that do NOT support Trueplay tuning:

https://support.sonos.com/s/article/3222?language=en_US

Yeah as guitar said. Try get an ios device. It fixed my problems trueplay, but likewise I feel your pain that it even requires it to be done on a £900 device.  

I’ve done all the fixes and I’m looking at 5.1 signals so it isn’t that the center is unused. I do have the speech enhancement on and I’ve tried night mode on and off. Turning down the Sub and Surrounds has minimal impact on the two systems that have them and I have the same issue on the one that doesn’t.

A fix that was suggested that I haven’t tried yet is to use a couple of the spouses throw pillows to further mute the left and right speakers. I may be reduced to this.

Came hear to register and reply to this topic.
 

I am enjoying my new Arc/Sub/One SL’s, but the quality of dialogue when watching normal TV in Stereo (2.0/2.1 audio) is surprisingly poor. It sounds tinny and flat on the Arc — it’s hard to follow even with speech enhancer on. Would like some extra control here.