No offense intended but honestly I don’t put a lot of stock in comments found on Reddit even though many swear by it. As in the case mentioned in Reddit and yours there are too many variables that can effect how things sound in one’s environment.

I have owned the Arc with Era 300’s and Sub 3 x 2 and have since transitioned to Arc Ultra with Era 300’s and Sub 4 x 2; but have never experienced the audio issues described. Granted there have been tweaks made by Sonos when certain sound anomalies were identified but none to the extent described in your post or those mentioned on Reddit, Quite frankly my setup sounds terrific!!

Variables that can affect your listening experience:

• Source content
• Room size (length, width, height)
• Room topography (extreme hard surfaces, extreme soft surfaces)
• Speaker placement for surrounds relative to listening position
• Sub placement to achieve optimum low end
• TruePlay tuning to balance accoustics which can also have the opposite effect to worsen acoustics 

As a start for this community to help you might post a diagram of your room showing its shape, seating, speaker placement and overall dimensions (L x W x H).  

it’s a rectangular room with 3 perforated melamine walls and ceiling, a wood floor and the wall where the tv is, is covered by a fabric acoustic panel. TV and speakers are placed symmetrically in the room. Sub gen 3 is on the left side of the TV.

Dimensions are something like 3.5m L x 4.5m W x 2.8m H 

Thanks for the picture. Very Nice!!! 

From what I can see the topography of your space is on the soft side with materials that absorb sound.  The fabric acoustic panel may not be the best material either for Sonos. I say Sonos because you may have had a professional installer who recommended the panel based upon traditional wired speakers. Sonos recommends; as does Dolby Labs, walls and ceilings that are smooth and not perforated as the surround “bubble” depends highly on surfaces that reflect sound waves rather than adsorb them.

Also it appears that the seating areas on each end are outside the surround “bubble”. I would also suggest placing the sub in different locations around your space to see where the low-end sounds best. Even placing the sub behind the seating areas may be an option as well although I think probably not.

Finally, I’d sound the space with and without Trueplay to see if it improves or worsens the acoustics. With TruePlay off you can fine tune the rears to your preference.

I think it's because center channel is too loud

Sonos need fix that asap anyway

Floor is hard. 3 walls and ceiling have perforations but otherwise are hard surfaces. And as i said this was not always a problem. It used to be better.

Hi All

I have made the following post which you may be interested in:

Please be aware that the change made may not relate to the specific problem stated here, but you may find that you will want to try adjusting the setting after installing the update, just to see if it improves matters for you in any way.