I'll add another detail…

It sounds like everything coming thru the surround speakers is being sent thru a "WaWa" guitar amplifier.

When set up as surrounds, there is no delay on the digital input to the Arc. However, when you ‘group’ them as two or more Sonos ‘rooms’, there will always be a 75ms delay between the Arc and any/all grouped rooms, designed for Sonos to buffer the signal so it can be played in sync on the rest of the rooms.

If you set up the two Era 100s as surrounds for the Arc, you’ll get rid of the delay. As long as they are in separate Sonos ‘rooms’, and grouped, there will be the delay on the input from the TV.

Note, this ‘delay’ goes away when you’re streaming music, and not using the TV’s input. Then you pay that delay before all the speakers play, and both the Arc and the Era’s rooms will be in sync.

finity,

It would be best if you submit a diagnostic and work with SONOS support. This will document the issue for developers.

If you do not want to invest the time to do this, I recommend that you remove the 100’s from ARC, reboot ARC, and Factory Reset (only) the 100’s. Then you’ll need to add the 100’s to your system as new speakers, and “bond” them as surrounds. Do not bond the 100’s as a stereo pair. Take care to avoid setting up a new system.

One part of your original statement suggests that you may be attempting to add a second pair of surrounds. This is not supported and any attempt to do this (by Grouping) will yield your symptoms when listening to TV audio. Before adding the 100’s as surrounds you should have removed the ONE SL’s as surrounds. The ONE SL’s can then be bonded as a stereo pair and used in another room if you like.

But it's not a delay. It's a WaWa reverb. The sound from the surrounds is in sync with the arc but it has a WaWa effect as it's playing. 

And as I stated, the speakers aren't grouped. They are set as surrounds.

I wish I could post a recording of the sound here but I don't know how I could do that.

@buzz

I'm not trying to add a second set of surrounds. I removed the original one's and the added the era100' as surrounds. I now have the original one's as a set of surrounds for a beam I have in a different room.

I’d agree with @buzz, and with you, there should be no ‘reverb’ from a pair of surrounds. You should indeed submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

I guess I’ll need to do that.

I tried the previous advice to remove, factory reset and re-add the ERA’s as surrounds but the issue still persists.

submitting the diagnostics within 10 minutes should be no problem since it happens pretty much constantly. 

Thanks for your help

@finity 

Just an idea… because you told nothing about the audio source (just that it’s tv mode) and the audio format of the content and the format shown in Sonos app. 
 

 Did you run Trueplay?  Maybe that’s a scary prospect with the new app.  I have Arc-300s-Sub that were Trueplayed before the new app was released.  No echo here.  Just grasping at straws here, but did you look at distance settings for the surrounds.  Those settings aren’t very detailed though.

Well...that was easy…

After contacting support the tech was able to quickly find the problem.

It was because I had the Wifi disabled on the Arc.

But it kind of doesn’t make sense since the Arc is hardwired to the router. So of course I thought I should disable the wifi on the Arc. But apparently you can’t do that because the Arc has to have wifi enabled to effectively communicate with the surrounds since they aren’t hard wired so they use the Sonos mesh to communicate.

I think there should be at least a warning somewhere that disabling wifi could cause playback issues for wireless devices or maybe even automatically re-enable the wifi once wireless surrounds are added...or preferably both.

Also it was even less obvious because I had the wifi disabled on the Arc as well when I previously had the one’s paired as surrounds and I never had that issue. 

Anyway it seems to be OK now.

Yeah, I’ve heard that Trueplay is/was having issues so I’m not sure I’m ready to use that yet.