era 300’s not using rear channels.

 That’s how they are supposed to work as surrounds.  The  side and top speakers work while the front speaker is disabled.  The surrounds are not supposed to project direct sound that makes their presence apparent.  They are meant to create a sound field behind, to the side and above you.  Best in a room with symmetric reflection surfaces.  Tough to do in an open architecture great room.

Hi thanks for the reply.

ok so let me just make sure I understand:

the inner tweeters of the era 300 (essentially the rear channel - not the outward tweeter) are not supposed to fire when in surround mode? 
 

what the issue is, is the outward firing tweeter and top firing tweeter are working. The inner firing tweeter is not working but I hear the bass tones is all - no actual sound permits as a surround effect from the inner tweeter. I am not speaking of the front firing driver - I know this one is disabled. The video does show this. Unless this is normal, I am hoping sonos can fix it. 
 

it seems that the height channel is taking over for the inner tweeter for some reason

this is ok? Others on that reddit post I pasted seem to be affected as well. 

 First I must state I have an Arc, not an Arc Ultra.  Ran the Dolby Atmos channel ID 7.1.4 test track on Functional Testing Dolby Labs ( available on Apple Music & Amazon Music Unlimited ).  The three separate channels being used in the ERA 300 speakers are being used starting with the out board side drivers then the inboard side drivers and last the top drivers.

 don’t know what the results would be if the soundbar was the Ultra.  Could someone with the Ultra try this and let us all know what you hear in the 300s?

This is also happening to both of my era 300’s. So for sure it’s not two defective products. I bought everything at once a week ago. This appears to be software related. 

 Are you saying yours behave the same way as mine when using that Functional Testing Atmos channel ID track?  Is that not how it’s supposed to be?  The OP talks about rear speakers in the 300.  Those were never called out for in the test.  The back plate of the 300 has no speakers.

No. The side firing (left and right) and upward firing all are supposed to work with surround and atmos content. Front firing driver is disabled for all of this.

what you are hearing on your devices is correct (all three channels [upward, left and right]) should be firing their sound during that test.

my two era 300’s are not firing anymore on all 3 drivers during movies or the channel test. Only the upward firing and outward side firing are working. The inner side firing is not working. Same with other users based on that reddit post. All 3 tweeters should be firing off sound during atmos content and the channel test.

the inner-side firing speakers are for “rear effects”. The outward side-firing speakers are for “surround effect”. 

 I see now.  I’ll have to listen more carefully.  All I heard was sound coming from the side.  Was not aware some of them were not working.

Just here to add to this thread and say that this very issue is being discussed here by the OP of that Reddit post. If anyone else is experiencing this issue, please add a comment here so that Sonos can see how wide spread this issue is. I understand that not everyone with this issue will realise that it’s happening to them and not notice their rear channels missing during Atmos content. But getting this resolved will improve that content for everyone drastically, even if they haven’t noticed this was happing to them before. 

I can confirm this is happening with test tones, as well. Rear surround channels are firing from the upward firing tweeter. 

Was looking into this and found this thread. I too -just purchased the system 300’s and Arc Ultra; and can confirm that some thing in the firmware is not firing correctly with that content. 

I did try confirming the output from the Era’s and Arc Ultra using the xbox dolby settings on my Series X. The output from the xbox is correct. 

Maybe that Dolby contents metadata is being read incorrectly by the Era’s and Arc Ultra. I’m unsure how to else test it with an actual game or actual content from say Netflix, Bluray, etc. 

I’m having the same issue.  Yes the front facing speaker is and always has been disabled.

What’s happening here is that the inside speaker of the e300s on both sides (rears) and rear height speaker seem to be behaving the same and not firing independently. When you play atmos rear channels from test files (I’ve used Nvidia Shield TV Pro and AppleTV 4K) it just plays through the rear height channels instead.

Outside speakers (side surrounds) both working just fine.