Height layer separation in a 7.1.2

Nidhoggr

Novice Member
Hi all,

I am doing the wiring for a 7.1.2 Athmos setup in my basement. I have indicated the ground layer speakers in blue, and the athmos on-ceiling speakers in green. (The positions are not exact.)
basement_electric.png


Surround rears
Behind front stage there are a number of empty tubes for wiring. One of them connects to the place I marked RR (rear right), and another to the RL mark. The thing is, the tubes exits the wall where the wall meets the ceiling. It would make a nicer looking installation if I could place the rear speakers at that height. However, that would put them as high as the Athmos on-ceiling speakers, and I am concerned about the perceived height separation between the two sound layers. It will almost be like a 5.1.4 rather than a 7.1.2. The ceiling is only at 2.27 m height, and since the rears are so far back compared to the main listening position, the vertical angles between MLP and rears will be quiet shallow, so maybe that makes it OK?

Surround sides
As far as I understand surround sides (SR and SL in drawing) should be slightly behind the seats and tweeter at or just above ear level when seated, hence about 1.0 m height. Meanwhile the Athmos speakers should be aligned with the knees of the listeners, right? I cannot fit in-ceiling speakers, so they have to be mounted on the ceiling firing straight down. This means their tweeters will only be about 1.0 m above the surround sides in the vertical plane, and about 1.4 m distance in three dimensions. Is this going to be a problem? Is there a better solution to this? I think my ceiling is too low for reflective Athmos speakers.
 

gibbsy

Moderator
All of your base level speakers should be at a seated head height with the surrounds and rear surrounds slightly higher. Having any of those speakers at almost the height of the ceiling is not going to give you any separation from the Atmos domain with those rear surrounds.

Your surrounds, which you call surround sides can be placed just above a seated head height and in a 7.1.2 could be placed opposite the main seating but having them just a little back is fine. Your assumption that the Atmos speakers should go just above where you sit is correct.

Looking at the plan of your room it looks more suited to a 5.1.4 and would certainly take a 7.1.4. If you stick with 7.1.2 then the room correction on your AV amp will make the necessary adjustment to the levels of the rear surrounds.
 

Nidhoggr

Novice Member
All of your base level speakers should be at a seated head height with the surrounds and rear surrounds slightly higher. Having any of those speakers at almost the height of the ceiling is not going to give you any separation from the Atmos domain with those rear surrounds.
Thank you for the reply @gibbsy , that certainly helps. With a room height of 2.27 m, what do you consider the ideal height for the rears? ("Slightly higher" = +30 cm?)
Looking at the plan of your room it looks more suited to a 5.1.4 and would certainly take a 7.1.4. If you stick with 7.1.2 then the room correction on your AV amp will make the necessary adjustment to the levels of the rear surrounds.
Hmm, 7.1.4 sounds very tempting... AVR prices go up a fair bit with that many channels, however. I will see if I can stretch the budget. And how many visible cables in the ceiling the Mrs will approve of. :)
 

gibbsy

Moderator
Thank you for the reply @gibbsy , that certainly helps. With a room height of 2.27 m, what do you consider the ideal height for the rears? ("Slightly higher" = +30 cm?)

Hmm, 7.1.4 sounds very tempting... AVR prices go up a fair bit with that many channels, however. I will see if I can stretch the budget. And how many visible cables in the ceiling the Mrs will approve of. :)
20 to 30cm with that height of ceiling would be fine. You have to plan in advance with inceiling speakers as they have to be in the right place for both 7.1.2 and 7.1.4 as the front speakers will be in a different place. So if you cut holes for a 7.1.2 and then decide to go 7.1.4 then that's another four holes. I know what my missus would say and it would be unpublishable.

There is a simple way to work around a 7.1.2 with ambitions for 7.1.4 and that is to move the seating forward in a 7.1.2. Eleven channel amps are on the expensive side certainly and this has to be one of the worse times to look to buy because of the pandemic and all the problems it has brought.
 

Triggaaar

Distinguished Member
The ceiling is only at 2.27 m height, and since the rears are so far back compared to the main listening position, the vertical angles between MLP and rears will be quiet shallow, so maybe that makes it OK?
Work out the exact distance from ears to rears, both flat distance, and height, and then you can work out what the exact angle would be. That would help guess whether or not it would be too much.



Surround sides
As far as I understand surround sides (SR and SL in drawing) should be slightly behind the seats and tweeter at or just above ear level when seated, hence about 1.0 m height.
They only need to be just above seated height in order to assure that the seats and other people don't occlude the direct sound. As long as they don't, keep them as low as possible.


Meanwhile the Athmos speakers should be aligned with the knees of the listeners, right? I cannot fit in-ceiling speakers, so they have to be mounted on the ceiling firing straight down. This means their tweeters will only be about 1.0 m above the surround sides in the vertical plane, and about 1.4 m distance in three dimensions. Is this going to be a problem? Is there a better solution to this?
I think that's ok.
 

Nidhoggr

Novice Member
Work out the exact distance from ears to rears, both flat distance, and height, and then you can work out what the exact angle would be. That would help guess whether or not it would be too much.
Here we go!
Rear vertical angle to MLP: 20 degrees​
Max rear vertical angle (worst case, closest seat): 24 degrees​
and:
Rear horizontal angle: 45 degrees behind MLP (within Dolby specs)​
Do you think that vertical angle would interfere with the Athmos over head layer?

While I am at it, I might go with these as Athmos speakers:
Since I cannot fit in-ceiling speakers and bolting visible speakers on-ceiling generates serious wife aggro I was thinking I could experiment with them mounted on side walls and as up-firing speakers.

In the scenario where they would be on side wall:
Athmos vertical angle to MLP: 27 degrees (to the side)​
Looking at the Atmos specs pdf this angle is not directly specified but is drawn as something close to 45 degrees, so 27 is quite shallow. (90 degrees here would be a speaker right over the head of the MLP, meaning both Athmos speakers would occupy the same space which is clearly not desired)

Up-firing on top of front speakers:
Apparent vertical angle to MLP (after reflection): 38 degrees​
Not sure if that is preferred over side wall mounted direct firing speakers...
 

Triggaaar

Distinguished Member
Here we go!
Rear vertical angle to MLP: 20 degrees​
Max rear vertical angle (worst case, closest seat): 24 degrees​
and:
Rear horizontal angle: 45 degrees behind MLP (within Dolby specs)​
Do you think that vertical angle would interfere with the Athmos over head layer?
If you've got them to 20 / 24 degrees, I think that's pretty good. It's also a long way from your 2 Atmos, so I think it'd be fine. I'm surprised it's as low as 20 degrees, but I trust you got the calculations right :)


While I am at it, I might go with these as Athmos speakers:
Since I cannot fit in-ceiling speakers and bolting visible speakers on-ceiling generates serious wife aggro I was thinking I could experiment with them mounted on side walls and as up-firing speakers.
That's far from ideal. Why can't you have in-ceiling speakers?

In the scenario where they would be on side wall:
Athmos vertical angle to MLP: 27 degrees (to the side)​
Looking at the Atmos specs pdf this angle is not directly specified but is drawn as something close to 45 degrees, so 27 is quite shallow. (90 degrees here would be a speaker right over the head of the MLP, meaning both Athmos speakers would occupy the same space which is clearly not desired)

Up-firing on top of front speakers:
Apparent vertical angle to MLP (after reflection): 38 degrees​
Not sure if that is preferred over side wall mounted direct firing speakers...
If that's what you have to go for, go for them to the side, not over your front speakers. The 2 angles you're comparing there (in bold) are in different directions aren't they? One the the side (fine), one to the front (not so good with a .2 setup).
 

Nidhoggr

Novice Member
If you've got them to 20 / 24 degrees, I think that's pretty good. It's also a long way from your 2 Atmos, so I think it'd be fine. I'm surprised it's as low as 20 degrees, but I trust you got the calculations right :)
The rears are more than 3 meters back, so that make the angle shallow. That is dictated by the empty tubes the electrician placed for me, and moving them means exposing visible wire and hence wife aggro.
That's far from ideal. Why can't you have in-ceiling speakers?
Concrete ceiling with floor heating and what-not a bit deeper in.
If that's what you have to go for, go for them to the side, not over your front speakers. The 2 angles you're comparing there (in bold) are in different directions aren't they? One the the side (fine), one to the front (not so good with a .2 setup).
Yes the sound would clearly come from the sides in one case and from the front in the other. However, the angles in both cases indicates how much "above" the listener the sound is perceived to be (from a single speaker) as opposed to from the horizontal plane.
 

Triggaaar

Distinguished Member
Yes the sound would clearly come from the sides in one case and from the front in the other. However, the angles in both cases indicates how much "above" the listener the sound is perceived to be (from a single speaker) as opposed to from the horizontal plane.
So the point where the sound would reflect from the side speaker, and hit the listener, is at 27 degrees? That doesn't sound right. What's the distance from the side (where this reflecting speaker would be) to the MLP, and what height would the speaker, ceiling and MLP be?
 

gibbsy

Moderator
Concrete ceiling, if flat and between 2.3m and 4.25m would be ideal for upfiring speakers. Most modules now come with a dual purpose role of either upfiring or wall placement. I dare say the upfiring positions would meet with your wife's approval.
 

Nidhoggr

Novice Member
So the point where the sound would reflect from the side speaker, and hit the listener, is at 27 degrees? That doesn't sound right. What's the distance from the side (where this reflecting speaker would be) to the MLP, and what height would the speaker, ceiling and MLP be?
I realize I might be confusing you with which angles I refer to so I made some drawings. Not very skilled with SketchUp so have pity! :) Yes that is my wife phoning her mum telling what a crazy man she married.

In the horizontal plane we have the azimuth angles. Same as we see in Dolby specs.

When I say vertical angles I mean the angle from the horizontal plane at seated ear height (~1m) to where tweeters will be located. So in the case of wall mounted direct firing Athmos speakers, they are 0.7 m forward, 2.1 m left/right and 1.1 m up -> 2.5 m from the MLP. arcsin(1.1/2.5)=26 degrees. I think I got 27 yesterday since I did not move speakers forward.

The same way the rears when mounted flush against the wall get a vertical angle of 20 degrees simply by being further away.
 

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Nidhoggr

Novice Member
Concrete ceiling, if flat and between 2.3m and 4.25m would be ideal for upfiring speakers. Most modules now come with a dual purpose role of either upfiring or wall placement. I dare say the upfiring positions would meet with your wife's approval.
That is good news, I remember the lower limit being too high for my scenario (like 2.5 m or similar), but 2.3 is only 3 cm from being within specs. I will likely get dual purpose angled speakers and experiment with positioning, the but the prewiring in concrete walls is a pain with a fixed position as it is already...
 

Triggaaar

Distinguished Member
I realize I might be confusing you with which angles I refer to so I made some drawings. Not very skilled with SketchUp so have pity! :)
They're fine for purpose :)


Yes that is my wife phoning her mum telling what a crazy man she married.
Join the club.


When I say vertical angles I mean the angle from the horizontal plane at seated ear height (~1m) to where tweeters will be located.
Yeah that's what I thought you meant, but I thought you were talking about bouncing the sound off of the ceiling, which would of course be a lot more than 27 degrees. I didn't realise having them at the top of the wall (where it meets the ceiling) would also be an option.

I'm not really sure which option would be best. If you have a low back on your sofa, so your side surrounds (at 100 degrees) can be close to 0 degrees vertical, then having atmos speakers above, at 27 degrees, would be very close to Auro 3D specs, which is currently my preference. In that situation you could have Auro 3D 9.1 (5 base layer, 4 top layer) and not use the rears. You'd also want speakers above the front speakers for that. It can be done to match both Auro 3D and Atmos specs (as well as DTS).

I appreciate that could be throwing another spanner in the works, but it's better to think about these things now, than after you've got your amp and positioned your speakers.
 

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