The perfect sound circle? - Home Theater Forum and Systems - HomeTheaterShack.com
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post #1 of 14 Old 09-22-08, 06:57 AM Thread Starter
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The perfect sound circle?

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.

Last edited by maikeldepotter; 09-22-08 at 10:41 AM.
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post #2 of 14 Old 09-22-08, 07:11 AM
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Re: The perfect sound circle?

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


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post #3 of 14 Old 09-22-08, 07:15 AM
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Re: The perfect sound circle?

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.

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post #4 of 14 Old 09-22-08, 10:14 AM Thread Starter
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Re: The perfect sound circle?

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bpape wrote: View Post
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...

Last edited by maikeldepotter; 09-22-08 at 10:30 AM.
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post #5 of 14 Old 09-22-08, 10:31 AM
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Re: The perfect sound circle?

Definitely let the processor account for the difference.

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post #6 of 14 Old 09-22-08, 02:46 PM Thread Starter
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Re: The perfect sound circle?

Quote:
bpape wrote: View Post
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....
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post #7 of 14 Old 09-22-08, 03:02 PM
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Re: The perfect sound circle?

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.

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post #8 of 14 Old 09-22-08, 03:31 PM Thread Starter
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Re: The perfect sound circle?

Quote:
bpape wrote: View Post
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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post #9 of 14 Old 09-22-08, 07:53 PM
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Re: The perfect sound circle?

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.

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post #10 of 14 Old 10-02-08, 11:55 AM
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Re: The perfect sound circle?

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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