# The perfect sound circle?



## maikeldepotter (Jan 10, 2008)

Hi,

Last week I found, and bought two second-hand surround speakers that I have been trying to get my hands on for some time, to complete my 5.1 movie surround system. Now I am in the process of determining the ideal positions for these on-wall speakers. This is what I have learned by lots of reading on this forum and other sources:

- All speakers should be positioned equidistant from the preferred listening position to create the best sound field. In my case this means on a circle with a 2.2 meter (about 7 feet) radius, with my head being the center.
- The listening angle for Center, Front and Surround speakers should be resp. 0, 30 and 110 degrees
- Front and Center speaker shoud be at ear level. This is 0.8 meter (about 3 feet).
- Surround speakers should be 2-3 feet higher then ear level. This is 1.4-1.70 meter (5-6 feet)
- Sub position is less critical and more determined by best bass performance. In my case: front firing between left Front and Center speaker.

Now here is my problem:

It is impossible to put your surround speakers 2-3 feet higher than your fronts on "the perfect circle", and at the same time maintain an equidistant position. You either have to leave the perfect circle, or sacrifice the equidistancy.

Question: What is the best choice?

Thanks for replying,

Maikel.


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## atledreier (Mar 2, 2007)

Most surround processors have delay or distance adjustments, so don't worry about equidistant. Your processor will handle that.


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## bpape (Sep 14, 2006)

I think you need to relook at the surround positions. 110 degrees is about the min I'd consider. Farther back will give you a better surround field in 5.1.

Speakers should (in the rear) absolutely be up higher, close to 6.5' off the floor. If you're going to try to keep them equidistant, it's not impossible. You simply have to take a straightline measurement in 3 dimensions instead of just length and width. When adjusting your processor delay, it's going to look at it this way anyway.

Bryan


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## maikeldepotter (Jan 10, 2008)

bpape said:


> I think you need to relook at the surround positions. 110 degrees is about the min I'd consider. Farther back will give you a better surround field in 5.1.
> 
> Speakers should (in the rear) absolutely be up higher, close to 6.5' off the floor. If you're going to try to keep them equidistant, it's not impossible. You simply have to take a straightline measurement in 3 dimensions instead of just length and width. When adjusting your processor delay, it's going to look at it this way anyway.
> 
> Bryan


OK, so if I put the surrounds at 2 meter (6.5 feet) high, and at an angle of 115 degrees (or do I have to move them back even further?) from the listening position, then I am close to the reference situation, i.e. the speaker placement in the surround recording studio? Doing so will destroy my "two dimensional circle", which I have come to understand is of no importance. Keeping them equidistant ("the three dimensional circle") is then still possible. However, in my situation I think I will have to move some walls closer to each other (wall mounted speakers). A better option is to let my processor correct for the longer distance of the surrounds...


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## bpape (Sep 14, 2006)

Definitely let the processor account for the difference.


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## maikeldepotter (Jan 10, 2008)

bpape said:


> Definitely let the processor account for the difference.


Hi Bryan,

I am getting a bit confused here. All info I get when searching for rear speaker placement in 5.1 movie setting (including the official Dolby site) is 90-110 degrees and 2-3 foot above ear level....:dontknow:


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## bpape (Sep 14, 2006)

OK. So how is that different? 110 degree placement and 6.5' off the floor fits that bill perfectly. How far away they are from you will simply vary with seating distance/room width. The processor will still detect the distance they are from you different than your mains distance and account for it appropriately.

Bryan


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## maikeldepotter (Jan 10, 2008)

bpape said:


> OK. So how is that different? 110 degree placement and 6.5' off the floor fits that bill perfectly. How far away they are from you will simply vary with seating distance/room width. The processor will still detect the distance they are from you different than your mains distance and account for it appropriately.
> 
> Bryan


Well, I am referring to your following statement: 

_"I think you need to relook at the surround positions. 110 degrees is about the min I'd consider. Farther back will give you a better surround field in 5.1."_ 

This has let me to believe that 110 degrees is not an optimum in your view. 

I just found the following remark on wikipedia which supports your remark:

_"Placement: 5.1 speaker layouts should conform to the ITU-R **.775 standard, despite the myth that music and video content require different placements. The ITU standard states that the left and right speakers are located at ±30˚, while the rear speakers should be positioned approximately ±110˚. *There is speculation that rear loudspeakers at ±150˚ provide "more exciting surround effects*".[6]"_

I suppose I have to listen and see what works best in my room, but I still appreciate any comments/views on the "official" recommendations and the speculations on better working layouts.


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## bpape (Sep 14, 2006)

I personally agree that with 5.1, I prefer the surrounds to be more behind me. Far be it from me to disagree with the inventors of 5.1 Dolby surround - I just know what I like. Now, in a 7.1 setup, 90-110 degrees for the side surrounds WITH another pair of rear surrounds is just about perfect IMO.

Bryan


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## Lonely Raven (Aug 27, 2008)

So much conflicting information on rear channels. I was going to post a similar question, but I figure I'll just let my ears guide me.


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## maikeldepotter (Jan 10, 2008)

Lonely Raven said:


> So much conflicting information on rear channels. I was going to post a similar question, but I figure I'll just let my ears guide me.


Listening is the ultimate goal and therefore IMO by definition the best criterium when trying to find the optimal speaker arrangement. However, since my surround speakers are wall mounted I want the amount of drilling holes in my beautifully plastered walls to be kept to a minimum.

This is what I found to be the theoretically best 5.1 set-up for my room. It is largely based on ITU standards - since they represent most closely the arrangement used in recording/mixing studios - with some small variations on speaker toeing (deviation from pointing exactly at listener position) to either enlarge the 'sweet spot' or comply to the recommendations of the speaker manufacturer for optimal stereo listening.

My room measures 11' long, 15' wide and 8' high. The front wall has no corners since it opens up to another room and staircase by a 3' wide passage on both sides. The back wall is a double glass window covered by net curtains and blinds. Seating position is 3' from back wall and listening height is 3'.

Listening distance to all 5 speakers: 7.5'
Listening distance to sub woofer: 6.5'
Center: 2.5' high, 0 degrees horizontal, 3 degrees vertically toed-up
Fronts: 3' high, 30 degrees horizontal, 20 degrees toed-out (as compared to pointed at listener)
Surrounds: 5' high (15 degrees vertical), 110 degrees horizontal, 20 degrees toed-out (firing straight at each other)
Sub: on the floor between left front and center

Planning to put the surrounds on the side walls this weekend...


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## Lonely Raven (Aug 27, 2008)

I'm in a similiar situation in that I can only drill holes in the walls *once*. I have no way to replace the textured wallpaper as I've not found the vender the previous owner of the home used. 

I wish I could just fun-tack my speakers up in different areas to find the best sounding spot! LOL


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## tonyvdb (Sep 5, 2007)

Lonely Raven said:


> I'm in a similiar situation in that I can only drill holes in the walls *once*. I have no way to replace the textured wallpaper as I've not found the vender the previous owner of the home used.
> 
> I wish I could just fun-tack my speakers up in different areas to find the best sounding spot! LOL


For a 5.1 system placing the speakers on the rear wall as said at about 6.5 ft up is the best placement and allows one to still walk under them without banging into them. Spacing them evenly on the back wall is even more crucial, for a 5.1 setup they can be placed near the corners (not in them) and for a 7.1 system should be about 4 ft apart plus in both setups should be at least 3 ft behind the rear seating.


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## salvasol (Oct 31, 2006)

I wouldn't worry to much as to form a perfect circle ... like Bryan said, let the processor adjust the delay, distance, etc.

Just be sure to have some accoustic treatment on the walls to help with the sound.

You have to work with the room you have (most of the time is not a perfect room) ... just try to set up everything the best you can :yes:


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