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Delay in 5.1 systems and grouped rooms

  • 2 December 2019
  • 6 replies
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I’m having trouble understanding the oft-discussed delay in sound coming out of speakers receiving input from different sources or speakers in different rooms.  I understand the ~70ms delay that is caused when a single source, like a receiver, is feeding a set of legacy speakers at the same time feeding through the “line-in” on say a Play-5 or Connect.   That makes total sense to me.  

What I’m having more trouble understanding are the discussions about a delay between the sound coming from the speakers in two rooms when one room, that is set up as a 5.1 surround system, is grouped with another room that is not but has Sonos speakers.   I called Sonos support and they said that there is no delay in that case and that the only delays are caused by “line-in” situations.  They did also say that there was functionality in the Sonos app to modify the delay in 5.1 systems but that seems like it was only to address delays between Audio output from the speakers and Video output from the TV.  

But then there are discussions in the community that say the exact opposite, like this one.  (search “delay 5.1” to find this)

Question:  “…. It seems the best option for me for surround sound is the 5.1 Playbar with 2 rear speakers and the sub. However, I can't seem to find a definitive answer on whether this can be extended with another SONOS speaker into the Kitchen or not.”

Best Answer: “...you won't be able to synch the sound. There's a built in 70 to 75ms delay between the 5.1 room and any grouped rooms”

So which is it?  We are building a new house so I’m in the process of setting up the layout and wiring.  I want a 5.1 surround system with playbar in the living room and Sonos speakers in the kitchen that can be played simultaneously without delays causing and echo.  

thanks for the help!

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Best answer by Airgetlam 2 December 2019, 23:36

Think of Sonos as having two types of “rooms”, defined by the root device in that room. A sound bar creates its own signal on the 5Ghz network, which is short distance but low latency. The SUB and surrounds connect to that network.

In order for a normal Sonos system to work, all speakers need to be able to play in sync. The system uses the 2.4 GHz network in order to reach longer distances through various materials. But in order to be able to sync across so many speakers, there’s a built in lag, which you only perceive when using a line in. 

But when connecting a sound bar “room” to the rest of the Sonos system, there are two things that need to occur. First, you have to translate the signal from 5.1 to stereo, and then you need to buffer that signal so it can be played in all rooms simultaneously on the 2.4 GHz network, rather than the 5Ghz network used by the sound bar.

This is why when your streaming music to the system, all speakers are in sync, since they’re all on the 2.4Ghz network. But when you’re taking the input from the sound bar to the other speakers, you need to pay the buffering tax.

At this moment, Sonos does not have the capability to play a TV input in sync with other rooms, only the one room that has the input in it. It’s feasible that at some point, Sonos will rewrite the basic foundation of their system and change this feature, but I don’t see that happening soon. Sonos has always been a whole home music system first, and their home theater product company second. 

I’m not sure how a company could do what you want. There are laws of physics, but I suppose there’s always a way around that being thought of by someone much cleverer than I am. 

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Think of Sonos as having two types of “rooms”, defined by the root device in that room. A sound bar creates its own signal on the 5Ghz network, which is short distance but low latency. The SUB and surrounds connect to that network.

In order for a normal Sonos system to work, all speakers need to be able to play in sync. The system uses the 2.4 GHz network in order to reach longer distances through various materials. But in order to be able to sync across so many speakers, there’s a built in lag, which you only perceive when using a line in. 

But when connecting a sound bar “room” to the rest of the Sonos system, there are two things that need to occur. First, you have to translate the signal from 5.1 to stereo, and then you need to buffer that signal so it can be played in all rooms simultaneously on the 2.4 GHz network, rather than the 5Ghz network used by the sound bar.

This is why when your streaming music to the system, all speakers are in sync, since they’re all on the 2.4Ghz network. But when you’re taking the input from the sound bar to the other speakers, you need to pay the buffering tax.

At this moment, Sonos does not have the capability to play a TV input in sync with other rooms, only the one room that has the input in it. It’s feasible that at some point, Sonos will rewrite the basic foundation of their system and change this feature, but I don’t see that happening soon. Sonos has always been a whole home music system first, and their home theater product company second. 

I’m not sure how a company could do what you want. There are laws of physics, but I suppose there’s always a way around that being thought of by someone much cleverer than I am. 

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That is such a clear explanation!  Thank you.  It makes total sense now including the previous exchange I quoted which was about output from the TV.    One additional question if I may.  I am planning to run Cat6 cables to all of the speakers since I have to run power anyway and I found a nice power/low voltage single gang box solution by Hubbel.  If the speakers are all connected via Cat6 would this eliminate the problem with the delay trying to synch the TV signal across rooms?  And if one has the speakers all connected to Cat6 cable, how should all of those wires terminate on the other end.   

Wired or wireless makes no difference. The 70ms buffer needed to sync grouped speakers differs from the 30ms or less you need to avoid lip sync issues between audio and video within the 5.1 HT.

Just in case it isn't clear... you can sync the TV sound across grouped rooms - at least approximately - by delaying the TV audio. But at the cost of worsening lip sync.

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John, delaying the TV audio may be a good solution if you are trying to listen to to a football game for instance where lip sync isn’t all that important.  Thanks for the replies!

Thank you for your kind comment, but please be aware I am neither a network engineer, nor a programming engineer. The data I presented are what I believe are a good representation of the Sonos system, based on years of usage, and the small amount of knowledge I do have. But I have never seen Sonos’ code (like that would make any sense to me!), nor has a Sonos representative laid all this out, to my knowledge. It is, however, generally accepted knowledge by the group of intelligent folks who help others in this forum. 
 

I am pleased to be part of that group of people, and try to learn when corrected, as most of them have deeper knowledge than I do. I just am verbose, so to speak ;)

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