Sonos Beam - Center speaker is mute (AirPlay only)

Yes. AirPlay 2 is just stereo, so there’s no data for the center speaker(s) to play. Once you hook it up to your TV, and feed it a Dolby Digital signal, that center channel will come alive.

@Airgetlam  Well, unfortunately it didn't… 

So I tried it with my “testing TV” that I use for work only, I hooked it up via ARC, set to audio mode to 5.1 and the result was very underwhelming to say the least. You are correct, the speaker started doing “something”, but only in very few scenes. For example in case of movie trailers (on Youtube) it is quite clear that the Beam uses ONLY the side (back facing) speakers as the stereo, which means that basically everything sounds like if you turn your normal speakers to face the wall. Very occasionally the three rear speakers starts doing “something”, basically only in the scenes that are supposed to be “in the center”, so most of the dialog sounds very muffled until it briefly starts sounding crystal clear (scene in the center of the screen) and than back to muffled stereo again. 

Is this normal pls?! I still think that my Sonos Beam is probably defective.

Might be worth double checking that whatever is feeding the TV (and the program you’re using to test with) is also 5.1. There’s lots of cases where set top boxes are just sending a stereo signal, which doesn’t really tickle the center speaker. You can open up your controller, and look at the description of the input for the Beam to see exactly what kind of signal it’s receiving. If it is anything other than Dolby Digital 5.1, you’ve got some investigation to do. It would be upstream, so either the TV’s settings, or whatever is feeding the TV set’s settings, or the program. In my area, many “talking heads” shows are only in stereo, I have to go to a movie channel which is playing a recent vintage movie (last 10 years or so) to ensure I’m getting a correct signal to test against. 

@Airgetlam Thanks for the info! Did double check everything, the TV was set to something different so I changed it to Dolby Digital, and Apple TV is already set to Dolby Digital 5.1, there is nothing else. Not sure which “controller” do you mean though pls?

Anyway I I tried few more trailers on YT from the modern movies (Avengers), still the same - mostly it just streams sound “behind” the bar (stereo) and the middle is mute (or almost mute), so I can barely understand what they are saying over the bass line. Occasionally some voice starts coming from the center right “in your face”, which sounds good, and then next voice is muffled and coming the wall again. Maybe the solution is to put it somewhere closer to the wall, behind the TV (or above)? Anyway this should not be the case, because it means that about 30-40% of the speakers are just not used most of the time, which seems like waste of money and it sounds very cheap this way.

Ok, did some more testing :) 

I tried the Apple TV show (one free episode) and it really seems like the voices are coming from the center speakers constantly, which is good. It is maybe just problem of trailers etc, where the narrators voice is being streamed only to “back” (L/R) stereo speakers. 

For the music it is almost unusable though, at least from the Youtube, since that is purely stereo and therefore the front facing speakers are (almost) off. The same with some other videos, although Podcasts (as the Apple TV app) and some talk shows on YT (Conan) use ONLY the front (center) speakers. 

I would be very much interested about how the Apple Music on the Apple TV will deal with this, since I dont have any account on my companies Apple TV (which I am using for testing right now). Will it automatically “spread” the sound over all three channels, event older tracks? Would be awesome if someone would test that for me since this will be my main usage of the Beam :) thanks!

Just addition to my previous “testing”, only certain videos of Conan show on YT are using the front speakers, some of them are just stereo. And in some cases the monologue is center and the rest of the video is from back (stereo) again, so you can clearly hear the first part but for the second part you must crank up the volume to understand clearly :D wow, what a mess...

All YouTube videos are stereo. Or they were last time I looked.

https://www.preteraudio.com/post/does-youtube-video-support-surround-sound

@Airgetlam Not sure about the terminology, but I can confirm for sure that some parts of YT videos (monologue od Conan O'Brien) are playing just from the center, while the rest of the video (skit) is playing just from the back (stereo) speakers. One way or the other, almost half of the soundbars speakers are not used at any point, which is mind boggling to me.

Have you looked in the controller to see what the Beam is receiving? Sonos reports what kind of signal it is getting from the TV set. 

YouTube videos are about the worst thing to be checking. Use Netflix, or HBO, or almost any other streaming video service other than YouTube.