Surround Sound 5.1 Speaker Placement

[Jester]

I’m planning on having a 5.1 surround set up in my control room. My three front speakers will be Event ASP8s and my rear speaker will be ASP6s. All 5 will be soffit mounted. My L and R speakers are angled 30 degrees (60 total) and my rear speaker are at 113 degrees. I am drawing it all out in SketchUp but I have a question about speaker placement. I have seen it recommended (by Rod and others) having the L and R speakers laid out from a point 16” behind the listening position. How does this apply to a surround layout? Should I have all of the speakers equidistant from the listening position then angle the R and L speakers to point 16” behind the listening position? Should all of the speakers be measured from a spot 16” behind the listening position? Or should I discard using a point 16” behind the listing position?

[Jester]

I found a thread (that I started) where John seems to be asking the same questions as me. http://johnlsayers.com/phpBB2/viewtopic ... +jpg#p5795
As that post is 6 years old I'm wondering if you ever found an answer John. My understanding is that in a stereo setup the speakers are aimed at a spot behind the mixers head to create a decent sized sweet spot. It would seem to me that it would still make sense to do this in a surround set up with the L & R speakers.

[Soundman2020]

You probably need to look at this:

http://content.grammy.com/PDFs/Recordin ... _1_Rec.pdf


- Stuart -

[Jester]

Thanks Stuart, I have read it and every other document and post I can find on surround sound. All of the surround sound literature I have read has all of the speakers equidistant from and aimed at the listing position. Yet it is fairly standard in a stereo set up to have the speakers aimed behind the listing position. As I will be just be using the L and R speakers the majority of the time it seems like having them aimed behind me would be best. I would love to find some info or research relating to this.

[Soundman2020]

The way I understand it is that with "aim point behind the head" then the acoustic axes of the speakers will be aiming directly at your ears (since your head is round, and your ears are on the outside! ). If you look at the geometry, it makes sense. If you were to aim the speakers so that the acoustic axes intersect in the middle of your chair / middle of your head, then they would actually be aimed in FRONT of your ears, so your hearing apparatus would not be perfectly "on-axis". That seems to be the reasoning. And the same seems to be true for the rear speakers: you want the aimed slightly forward of your head, so that the acoustic axes intersect your ears.

But now that you mention it, I don't recall seeing any research documentation on this subject!. Hmmmmm..... So I'm wondering of it's just one of those "logical rules of thumb" about acoustics, that everyone takes for granted but few question...

- Stuart -

[Eric_Desart]

The way I understand it is that with "aim point behind the head" then the acoustic axes of the speakers will be aiming directly at your ears (since your head is round, and your ears are on the outside! ). If you look at the geometry, it makes sense.

It does.
I recently designed the acoustics (speakers integrated in design) for an multifunctional Aurophonie control room (first in the world) to combine different formats including stereo, surround and the Dolby standard for film.
That are a lot of speakers. I aimed them all (except centered speakers of course) to the ears (measured with laser) of a hypothetical individual, meaning these intersection are located depending on which speakers more or less outside the head and had no "one single" intersection point for all speakers.
http://www.aurophonie.com/

[Jester]

Very cool Eric and I thought figureing out 5 speakers was tricky. Did you measure the distance to each speaker from the ears or from a central point?

I think I will aim all my speakers at my ears (excpt my C which I will am at my nose ) so my LR will point behind my head and my rear speaker will point in front of me. I'm thinking I will still measure them from my center point.

[Eric_Desart]

Very cool Eric and I thought figureing out 5 speakers was tricky. Did you measure the distance to each speaker from the ears or from a central point?

We made a stand which had a fixed position, checked all lines passing these ears (bit difficult to explain), defined the intersections of the paired speakers and checked that they were in the exact center line of the room and so on.
The speakers were positioned versus their acoustic center, and since we used different types of the same brand (Genelec), I had contact with Finland to know the depth center for these types (not in the published specs) so that I started from a 3D acoustic center.

In fact the interior of the room is designed/adjusted in function of the exact positioning of the speakers.
The whole construction is done with laser.
But it doesn't matter how you do it, as long as you do it accurately.

And check my previous post again: I have no central or common intersection point covering all these speakers.