Atmos 5.1.4 speaker placement questions

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paulwgraber

Enthusiast
So I have been watching a lot of reviews and youtube videos re: a 5.1.2 vs 5.1.4 vs 7.1.2.
Due to the restrictions of my room and budget I have settled for a 5.1.4 setup due to room variations and budget.
Receiver will be an Onkyo RZ50. My Atmos speakers will be ceiling mounted.
So with that said my question concerning 5.1.4:

1. Atmos= Do I put one pair of atmos above and in front and one pair above and behind?
I have seen videos of some people saying directly above, a little in front, a little behind so on and so forth.

2.Surrounds= So where do I put my surrounds with 5.1.4? Behind me? To the sides?

Thx in advance
PG
 
William Lemmerhirt

William Lemmerhirt

Audioholic Overlord
Surrounds should be 90-110° to the sides. Atmos should be 45° in front and behind the MLP.

This diagram above is only for reference and not to any particular spec. Also, the lines that happen to make it look like the overhead speakers need to be in line with the mains does NOT mean that.
 
P

paulwgraber

Enthusiast
So with a 5.1.4 system with the Onkyo what channel does the Onkyo send to the back or surrounds? in other words if I have surround back speakers does it mix the side surround and back surround into one?
 
William Lemmerhirt

William Lemmerhirt

Audioholic Overlord
So with a 5.1.4 system with the Onkyo what channel does the Onkyo send to the back or surrounds? in other words if I have surround back speakers does it mix the side surround and back surround into one?
Basically yes. But you can’t have rear surrounds without regular “surrounds” regardless of where they are placed.
So 5.x.4 will have surrounds. 7.x.4 will have side surrounds and rear surrounds.
 
N

nicoleise

Junior Audioholic
in other words if I have surround back speakers does it mix the side surround and back surround into one?
If the source material is 7.1.x or higher, yes.

The total sound output in Atmos or other spacial formats will consist of the sum of the discrete channels (much like traditional surround) and the object audio sound. In a traditional mix (non-spacial), there are just the discrete channels, no objects.

As for the discrete channels: A simplified way to explain it is that the audio information in each configured channel is subtracted from the total mix and the remainder is assigned to the most relevant channel(s), based on information about channel pair and panning. So if you play back a mix containing channels that your system is not configured with, rather than omit the sound from the non-configured channels, the sound will be played by different (configured) speakers. Where the sounds will end up depends on the audio itself and the algorithm with which this process ("folding") takes place. But in the case of rear surrounds being absent, it's a fair assumption that most of what they were supposed to be playing is sent to the side surrounds instead. On the other hand, if you had a 6 ch system (a rear center), it might behave very differently by "gathering" the sound directly behind you instead of pushing it to the side surrounds). Especially as in some formats the rear surrounds were mono anyways.

But it's a good example of the advancement of spacial audio, because in this example, if you don't meet the channel configuration of the mix, in scenario A the sounds will be pushed up to the side of your head and on scenario B it will be even more concentrated directly behind you, depending on which layout you have, even if both are legitimate layouts, albeit different between DTS and Dolby. Hence also why Dolby and DTS mixes may treat the lack of surround rears differently.

This logic works the same whether you have only 2 ch, 3 or whatever, and its simple goal is to ensure compatibility by making sure all the audio actually gets played, even if you're "missing" speakers. Even if it may occasionally make for a slightly odd experience where sound is coming from elsewhere than intended, it's still considered best for the user to actually hear the sound.

As for objects, the receiver/decoder will dynamically assign them to the speakers in the configured layout that best matches the azimuth, elevation and size properties of the audio object. So obviously this will behave much more accurately in different channel configuration, providing speakers are placed where the receiver expects. This is essentially a large part of the point or progress that spacial audio represents, and also why it's so important to get the speaker layout right.

So; objects will use whichever speakers it should out of those available, while the discrete channel information is folded by predetermined rules to achieve the best compromise expected.

You can test this, because it depends on the configuration in your receiver. So if you playback some passage in a 7 ch movie a few times and pay attention to the sounds, and then replay with your receiver setup for 7 channels, you should notice sounds missing (because the receiver is now sending them to the non existing, but configured, surround rears, and also subtracting the audio from the "remains" on the basis that to the receiver, the sounds are assigned properly to the speakers).

You can also try the same with a spacial mix like Atmos, and see that while some sounds "go missing" in this test, objects will still fairly similar. And than the "rest of the sound" will still behave as above.
 
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nicoleise

Junior Audioholic
What. Are. You. Saying? This is word soup.
No sounds ever get tossed or go “missing”. They just get sent to available speakers.
I know we’re on different continents. But wuuuuuuut?
I absolutely understand if you don't want to read something, but then why respond to something, you clearly haven't read?

While I never mentioned that sounds "get tossed" or "go missing", for the benefit of your understanding, consider that the "folding" (or down mixing) algorithms need to also handle scenarios where other speakers may be missing/unconfigured. They are not just designed exclusively for this one use case.

And also consider that this methodology varies between formats, and within formats. In Dolby for example, there are more down mixing strategies to choose from.

An example Dolby of down mixing 7.1 to 5.1 with one such strategy will output as follows:

Ls = Ls + (Lrs-1.2dB) + (Rrs-6.2dB)
Rs = Rs + (Lrs-6.2dB) + (Rrs-1.2dB)

So as you can tell from just this one example, it's hardly as simple as "they just get sent to other speakers".

And again, this applies to discrete channels. Objects behave differently.
 
William Lemmerhirt

William Lemmerhirt

Audioholic Overlord
I absolutely understand if you don't want to read something, but then why respond to something, you clearly haven't read?

While I never mentioned that sounds "get tossed" or "go missing", for the benefit of your understanding, consider that the "folding" (or down mixing) algorithms need to also handle scenarios where other speakers may be missing/unconfigured. They are not just designed exclusively for this one use case.

And also consider that this methodology varies between formats, and within formats. In Dolby for example, there are more down mixing strategies to choose from.

An example Dolby of down mixing 7.1 to 5.1 with one such strategy will output as follows:

Ls = Ls + (Lrs-1.2dB) + (Rrs-6.2dB)
Rs = Rs + (Lrs-6.2dB) + (Rrs-1.2dB)

So as you can tell from just this one example, it's hardly as simple as "they just get sent to other speakers".

And again, this applies to discrete channels. Objects behave differently.
Hola. I offer my apologies. That was a late night drunk post. I’ve updated my post accordingly, and will reread yours.
 
T

Trebdp83

Audioholic Ninja
So with a 5.1.4 system with the Onkyo what channel does the Onkyo send to the back or surrounds? in other words if I have surround back speakers does it mix the side surround and back surround into one?
The receiver can contract or expand signals as necessary for the configured speakers. Using a 5.1.4 speaker configuration, 7.1 signals will have the surround back channel information output from the surround speakers.

The 5.1.4 configuration is preferred in some cases using Onkyo receivers. IMAX DTS 5.1 and some Dolby 5.1/ES signals will actually output surround information from the surround back speakers in a 7.1 or 7.1.2 configuration and nothing will be output from the surround speakers.

Using a 5.1.4 configuration, you can leave it on Dolby Surround and use all speakers in the system for most signals. A Dolby Atmos track will result in an automatic switch to Dolby Atmos mode when already set to Dolby Surround.

Every room has its own issues but try and get the speakers configured optimally in your particular space for optimal audio output.
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