How to Improve ARC ultra ( w more speakers)

Couple of things to check, first.

1. What type of signal is being sent from your TV to the Sonos Arc Ultra (ARC is a different ‘thing’, and stands for Audio Return Channel, usually)?
2. Make you’ve either run, or turned on TruePlay. 
    

Adding dedicated surround speakers and a Subwoofer certainly offloads some effort from the Arc Ultra, which may make a difference. It does depend on 1. above, however. If your devices are sending a stereo signal to the Sonos, it won’t make much of a difference. Make sure you’re testing with / sending at least a Dolby 5.1 signal. Some talking heads and sports events don’t always use the full capabilities. 

I have to ask….

Did you listen to the Arc Ultra before you purchased it?

I also have the latest Samsung TV model (two of them), and I haven't experienced any issues with the sound from the Arc Ultra... in other words, the Arc Ultra plays whatever signal is fed into the TV (connected via eARC). So, you should look for the problem in the connection and the signal path...

Had a similar disappointment with my Arc setup when I first got it, so a few things worth checking before spending more. First, make sure your Samsung is sending a clean signal: in the TV's sound settings, set HDMI audio output to bitstream and turn off any TV-side processing (virtual surround, adaptive sound, etc.), then let the Arc do the decoding. A TV that downmixes everything to stereo first is a very common cause of thin, harsh dialogue. Second, run TruePlay again from the main listening position, since placement near a wall or a TV cabinet can make the highs sound brittle until the tuning compensates. If you have not tried it, turn on Speech Enhancement and toggle Night Sound off, they interact more than people expect. As for your actual question: a Sub made a much bigger difference for me than surrounds did. Offloading the bass lets the Arc Ultra's midrange and center channel breathe, which is exactly where dialogue clarity lives. Era 100s as surrounds are great for immersion and movie effects, but they will not fix thin dialogue on their own. If budget is the concern, I would add the Sub first and see how much of the problem disappears.

If audio output is set to HDMI eARC, there is no need to turn anything off. The TV speaker disconnects, and the sound is routed to the soundbar... this applies to top-tier Samsung TV models from 2024 onwards... assuming you also have the latest firmware installed…

​@MK0117 

You mentioned that sound from the Arc Ultra is underwhelmed. The next question is...compared to what?

Your opinion is valued; but you’ve given very little context to support your claim or any type of benchmark comparison. Adding more speakers is not a solution as the Arc Ultra has been designed/tuned to perform at the highest benchmarks vs competitive soundbars. Check the review in this Link by PC Magazine (just one example).

My suggestion is to try the suggestions given by members in this thread. The Arc Ultra does a fine job on its own without adding surrounds and/or sub. However, those additions do help. TruePlay tuning is another option. Also, let’s not forget the shape and topology of the room the Arc Ultra has been placed in. Pictures and/or a floor diagram are helpful if you can submit them in this thread. 

As has been said if you feel there’s more going on that requires additional investigation please submit a diagnostic, make note of the reference ID and then call Sonos Tech Support.

Good Luck to get the Arc Ultra performing to your liking!

Do not publish the reference ID in this community and by all means do not factory reset the Arc Ultra.