I spent an hour or so on youtube and netflix to find some material that is longer then a few seconds clearly reproducing the issue… its more diffcult than I thought.

So for now, I have been falling back to testing with our superman video.

One thing to add, I disabled eARC on the LG TV, which leads to the audio channel falling back to “Dolby Digital Plus 2.0”.

I think I can say that the phenomenon is also clearly audible in this mode. So its not only „Dolby Multichannel PCM 2.0“.

Ken, I think this is the mode you also had, but an additional Feintech in the middle. So it would be really interesting to hear what taking the Feintech out of the loop would bring.

On the other hand, I played various 5.1 and Athmos tracks and in none of them heard anything like the distortion I have in 2-channel audio.

Call me old fashioned, but its kind of irritating anyway how many variants of “stereo” there are these days.

Anyway. In “Dolby Digital Plus 2.0”, with eARC disabled, also the sidewards pointing speakers are emitting audio also. So its pretty clear the Beam is doing some upmixing magic even on two-channel audio.

1. Yes sounds similar.

2. Sony x950h

3. Depends on what's playing. I've heard the sound in 2.0, 5.1 and Atmos. The app reports the correct format in each case. 

4. The problem doesn't change based on passthrough but I can't hear it when switched to PCM. 

Ok, I will try the things mentioned and will let you know if I am ever able to reproduce the issue here.

By the way you mentioned earlier about the Surrounds/Sub being disconnected, which I’ve been doing, but do you not notice it when you have your surrounds and/or sub enabled, even with that Superman video?

Are you able to provide some examples @Shnakey that you use to reproduce the issue - it would be helpful if there was more than the YT Superman video, even better if the samples are perhaps available on the streaming platforms, like Amazon, or Netflix, Movies/Shows etc. 

Thanks  

I would be particularly interested in something that is multi-channel, e.g. 5.1. Which I have not found in my setup.

I think it is a difference in our setups.

i have no sub and no surrounds. Not even configured nor set up, so I don’t need to disable them either. Could it be this changes upsampling behavior?

Yes possibly... maybe some others here with standalone Beams will chime in. I will test that too, when I have the chance. 

It can just be a bit of a nuisance bonding/unbonding surrounds & sub and having to re-truplay the room, so I’ll hang on and do that later perhaps, maybe after @Shnakey, or others here, post some further audio examples to perhaps test too.

I'll try and record some samples over the weekend and report back. 

Just perhaps point to some samples on Prime Movies, Netflix etc (with approx. times) as I’m still struggling to reproduce the issue here.

I am experiencing the same issue with appleTV 4K, Beam Gen 2 and Sub mini. First I thought it’s because of my Samsung TV only being capable of arc instead of eARC but I also notice it via the vax0101A. I feel like it happens less when running Atmos, but it constantly happens when playing PCM 5.1 multi channel. Currently forcing 2.0 via the vax to prevent it from happening. I think it’s less prominent for me with stereo.

I recently noticed the phasing behaviour in the movie „Barbarian“ (tw: crazy horror movie) on Disneyplus with English audio. I slightly noticed it during the movie in some scenes with rain in the background but it really stood out when the credits started and music kicked in at the end.

Same problem here.

standalone beam gen 2, Apple TV connected via the feintech. So we can rule out the tv.

A good example is Slow Horses on Apple TV+ (Atmos audio). Listen to the opening theme, that usually starts some minutes later. It’s a Rolling Stones track. Listen that on headphone on stereo and it sounds really different.

Technically you can describe it as a phasing issue, it’s like a very short delay that sums up to the original audio and cause cancellation in some frequencies, giving that “metallic sound”. It’s probably due to decoding issues BUT phasing can also be purposely used to create psychoacoustic effects to recreate space, so I’m not sure it is a problem or a features : ) maybe some people are more sensitive then others and are not tricked into believing that fake “space” but just ear phasing. I’m into this category.

I don’t have rears but my believe is that with rears you don’t have this problem, because you have real speakers to create space and you don’t need this kind of audio treatment. Probably it happens only with sounds that should came from the rears, but having no rears the beam decode them in this (not very pleasing) way. But I don’t have rears to test it so I cannot confirm it.

you can definitely making it less apparent setting height to 0. I set mine to 8 some time ago and from that moment I’ve started noticing the problem. 

it’s audio processing not well tuned. I really hope Sonos will refine it in the future, but I’m the only in the family that has noticed it, so probably is not an issue for many.

@Eriksatie haved you tried setting the height to -10? Does it sound worse than 0?

Yes I’ve tried, there’s little difference to 0 but probably can be different if you test another movie (or maybe another room?). Also don’t wanna lose all the verticality (the effect is so small even at +8). I think that everyone should find his sweet spot. Zero seems to be a nice start point and definitely sounds better then +8, at least to my ears

Update:

I think I have a conclusion for this topic. I have a pair of One’s here for a while and I’ve used them as rears together with the Beam gen. 2

I’ve listened to the same movies that has the metallic sound problem. with surrounds, the metallic sounds are not there anymore. In the opening theme of Slow Horses the music come both from the beams AND the rears, and I think this is what generates the issue. When all the channels that contains the music are played from just the Beam, the channels sum up into the beam speakers, but because there is some differences in the content of the channels (L, R, RL, RR) the sum is not perfect and generate delay/phasing issues (the metallic sounds). this also can happen when you listen to a stereo music track in a mono speaker, for the same reason.

I’m not an audio engineer but, if this is the problem, I don’t think Sonos can do anything about it. it just depends on how the audio is originally mixed through the channels. this also explains why the problem is not always present but just on some particular scene, when the same sound is delivered both from the front and the rear.

Dear Erik,

it is indeed very interesting that this does not happen with rears. It proves that it is some upmixing going wrong.

That said, I do not second your conclusion that nothing can be done here. For one, if it does not happen with rears also on stereo, that means stereo is upmixed to multi-channel also.

This is also in line with the my experience that the metallic sound is coming from the sidewards pointing speakers. These are probably the speakers used to create „3D“. So for heavens sake, don’t use them on stereo!

This upmixing of stereo is a feature completely useless and could be disabled altogether IMO.

Also, upmixing for multi-channel - if played without rears - may be something people want to disable, if the inevitable (is it really??) result would be metallic sound.

So the solution is simple, give us an option to disable upmixing (use of sidewards pointing speakers) -or- refrain from doing it in situations like stereo content.

Cheers

I’m just giving a theory here, but my impression is that it happens when the front and the rears are slightly different in timing, for example when the rear is slightly delayed. This is a very common technique used in audio mixing to give a sense of space. Can be used also in stereo tracks. You take the left signal, delay20-40 ms and send it to the right speaker. This gives you a “fake stereo” sound. This can be done also on 5.1 setup: you take the LR signal, delay it, send to rears and you have a “fake surround” signal. This is done by audio engineers that mix the audio of the film, not by Sonos speakers.

this trick works, but only if you use different speakers for the delayed signal. If you sum up the two signal in one speaker you are going to get a metallic/phasing sound and you can’t do anything about it. I have a background as a mixing engineer in music field and I’ve mixed a lot of music (stereo) tracks. When you are mixing in stereo you have to be careful about mono compatibility. The “fake stereo” I had explained before is something that can create problem for mono compatibility. In the same way, if you applied that trick to a 5.1 you can have problem with system that are not really 5.1 but try to emulate that (for example soundbars).

I might be wrong, I don’t have experience in 5.1 mix, but this explanation make sense to me and my knowledge

I am facing this issue right now with the Beam Gen 2 without surrounds. Can anyone confirm that adding surrounds resolves this issue?

for me, and for that specific problem, yes, totally. be sure to understand what this specific problem is, it seems that just a few people (including me) was sensitive to it.

Thanks for your response. I get metallic sound problem when playing games on a desktop PC.

I don’t get this metallic sound problem when I set the audio output to Stereo PCM mode - app shows “Stereo PCM”.

All other sound modes I tried (Dolby Digital 5.1, Dolby Atmos, Multipcm 5.1 / 7.1) will have this issue.

Do you get this metallic audio problem in Stereo PCM mode without surrounds?

No, at list I cannot remember of it. The only cases I clearly remember was Atmos or 5.1 movies. Never with stereo music. Now I have rears so I didn’t experienced it anymore