John Sayers' Recording Studio Design Forum Archive

Your CR needs to NOT have the mix position dead center front-to-back - more like I shifted it in a markup of your plan, only with the rear surrounds moved forward too, and the front left and right's pulled in and re-angled to maintain equilateral triangle - either that, or you need to make the room deeper - you do NOT want your head sitting centered front/rear, as it is already centered left/right for proper stereo - this would put you in two dead center null points in the room, with peaks as well.

Angles for sidewalls - 6 degrees will only take care of flutter echo. For RFZ, you need more. ONly by doing the geometry of the room and "ray tracing" from each speaker to walls and back, can you find out the correct angles. By showing this as a surround room, you probably won't be able to do RFZ at all, unless you use absorption where a stereo room would normally use hard surfaces.

You do show your speakers at correct distances, they should all be within an inch or less the same distance from your head.

Sorry, but it's after 3 am here and I have to go fight insurance companies tomorrow - will try to add more soon... Steve

PS – didn't get this posted last nite, ISP was screwing around with maintenance and kept losing my connection -

Hi Steve,

knightfly wrote:Your CR needs to NOT have the mix position dead center front-to-back - more like I shifted it in a markup of your plan, only with the rear surrounds moved forward too, and the front left and right's pulled in and re-angled to maintain equilateral triangle - either that, or you need to make the room deeper - you do NOT want your head sitting centered front/rear, as it is already centered left/right for proper stereo - this would put you in two dead center null points in the room, with peaks as well.

I did not understand that. Can you explain that in simpler words?
The Symetrie is with + - 30 degrees and +-110 degrees fixed, how the 110 degrees are a little flexible and the distance to the mix position should be the same, or not? But probably I did not understood this paragraph...

knightfly wrote:Angles for sidewalls - 6 degrees will only take care of flutter echo. For RFZ, you need more. ONly by doing the geometry of the room and "ray tracing" from each speaker to walls and back, can you find out the correct angles. By showing this as a surround room, you probably won't be able to do RFZ at all, unless you use absorption where a stereo room would normally use hard surfaces.

But is there an useful acoustic optimization between "Stereo CR" and "Surround CR"? I want to mix both. Normal Stereo mixes and also Movie surround mixes...

knightfly wrote:Sorry, but it's after 3 am here and I have to go fight insurance companies tomorrow - will try to add more soon... Steve

Good luck! I know what that means....

Regards
Hendrik

But is there an useful acoustic optimization between "Stereo CR" and "Surround CR"? I want to mix both. Normal Stereo mixes and also Movie surround mixes...

There are recommendations. Sorry, it is english and very large, but about the most comprehensive document I know of detailing the differences in mixing and acoustics for different environments is

http://www.naras.org/pe_wing/5_1_Rec.pdf

You can probably useful information in german for classicl and tv mixing in EBU documents. The T3276 and t3286 series of come to mind. I seem to remember the url is:

http://ebu.ch

Good luck!

edit: put some words into english and corrected the EBU url.

Hello, thanx for the link.

Is it true, that NOT all Speakers should "show" to the mix position?
In this 5.1 rec PDF I read, that the front LR Monitors should show 1 feet behind the Mix position and the rear LR should show 1 feet in front the Mix position. Why?

Regards
Hendrik

Is it true, that NOT all Speakers should "show" to the mix position?
In this 5.1 rec PDF I read, that the front LR Monitors should show 1 feet behind the Mix position and the rear LR should show 1 feet in front the Mix position. Why?

It is difficult to answer your question. If you post a link or at least title so that we can read the document, we can answer your question much better.

For starters, read the EBU t3276 abd t3276-s1 documents. I am certain you can get those in german off the EBU website (I corrected teh url in my previous post).

Sorry, damned ISP was screwing up so bad when I posted that I forgot the pic -

Are you familiar with room modes, nodes and anti-nodes? These are the problems I was referring to when talking about NOT putting your head exactly centered between front and rear walls, nor centered between floor and ceiling - by definition, your head must be centered left to right or you can't get a balanced stereo sound field. However, if you center your head in the other two dimensions, you will get huge peaks and nulls in the sound level at different harmonics of your room dimensions. This makes it nearly impossible to make valid decisions about a mix or to do a mix that will translate to other systems or other rooms.

The 5.1 pdf completely ignores room construction or acoustics as near as I can see -

In my next CR, I'm considering setting up for both stereo and 5.1 by making reversible inserts for the areas around the front of the CR, one side being reflective for RFZ stereo mixing and the other side being absorptive for 5.1 mixing -

The reason for this is that when you add rear surround speakers and a center channel speaker, you get new reflection paths that weren't there before - this makes it nearly impossible to get away from early reflections at the mix position which are caused by these extra speakers firing toward surfaces that previously did not have sound sources directed at them - the only way I've seen considered that solves this problem is to absorb these surfaces; specifically, the front hemisphere of the CR.

Not having tried it, I'm not sure you couldn't use a 5.1 CR with absorbed front hemisphere for also mixing in stereo, as long as you perhaps made other parts of the CR more "live" to compensate for the deader sound -

what the "founding fathers" of surround generally recommend for 5.1 mixing is to make the room quite dead, and then add the lost ambience back to the mix digitally. This is not something I think I'd like for stereo mixing, but I'm not yet at a point where I can say for sure. That won't happen until I get my new facility designed and built, which will probably take a few years yet.

Anyway, I marked up your CR drawing and put the desk more where it would need to be if you don't make the room itself deeper front to back - otherwise, you will be sitting in a very uneven sound field. Naturally, you would also have to relocate the center channel speaker to maintain equal distance to your head - also, the surrounds may have to move forward as well (although there is a fairly wide range of acceptable angles for the rear surrounds)

Did that help any, or am I still talking in circles? Steve

Steve:

The 5.1 pdf completely ignores room construction or acoustics as near as I can see -

If you are referring tot he grammy document you are correct that it ignores construction. As far acoustics goes, it defines what the results should be, without getting into at all into HOW to achieve it. what prompted my posting it was Hendrik's question about speaker placement and stereo/surround compatibility and music /movie style mixing. It (the grammy document) includes what the "founding fathers" of surround generally recommend for 5.1 mixing is to make the room quite dead, and then add the lost ambience back to the mix digitally. This is not something I think I'd like for stereo mixingtatements almost identical to your

what the "founding fathers" of surround generally recommend for 5.1 mixing is to make the room quite dead, and then add the lost ambience back to the mix digitally. This is not something I think I'd like for stereo mixing

and going even further noting that depending on the market being mixed for that surrounds may used for ambiance or localization.

Hendrik:

I hope I didn't overload you with information, but the questions you asking were getting into the underlying theories and concepts of room designs. With it being your room and your money, I felt that you should have the choice to study and understand these if you choose to.

Hi AVare,

AVare wrote: It is difficult to answer your question. If you post a link or at least title so that we can read the document, we can answer your question much better.

I mean your "Recommendations For Surround Sound Production" linked document... The 5.1rec.pdf!!! I readed it there...
When you follow this, you have´nt a exact sweet point... Why?

AVare wrote:I hope I didn't overload you with information, but the questions you asking were getting into the underlying theories and concepts of room designs. With it being your room and your money, I felt that you should have the choice to study and understand these if you choose to.

No, please tell me what you know! I am learning!...

Hi Steve,

knightfly wrote:Are you familiar with room modes, nodes and anti-nodes? These are the problems I was referring to when talking about NOT putting your head exactly centered between front and rear walls, nor centered between floor and ceiling - by definition, your head must be centered left to right or you can't get a balanced stereo sound field. However, if you center your head in the other two dimensions, you will get huge peaks and nulls in the sound level at different harmonics of your room dimensions. This makes it nearly impossible to make valid decisions about a mix or to do a mix that will translate to other systems or other rooms.

Now i understand what you mean! I know that, but i have´nt remember it.
Thanx that you tell me again. I will update my CR design....

knightfly wrote:The reason for this is that when you add rear surround speakers and a center channel speaker, you get new reflection paths that weren't there before - this makes it nearly impossible to get away from early reflections at the mix position which are caused by these extra speakers firing toward surfaces that previously did not have sound sources directed at them - the only way I've seen considered that solves this problem is to absorb these surfaces; specifically, the front hemisphere of the CR.

I understand, but it must be possible to make flexible Acoustic Systems, or not? Then I can design a "normal" Stereo CR and with putting some Absorber on, I have a 5.1. Ok it´s sounds to easy, but will it work?

Regards
Hendrik


P.S. I will update my plan tomorrow. We will see...

I mean your "Recommendations For Surround Sound Production" linked document... The 5.1rec.pdf!!! I readed it there...
When you follow this, you have´nt a exact sweet point... Why?

Okay, I went back to both your original post on this point and the 5.1 document. understand now. By "show" you mean aimed at.

The idea of a sweet spot is theoretical. If in reality there was just one specific sweet spot, then you wouldn't even move your head! The idea of aiming the speakers behind the main listening position is to increase the area where good imaging will occurr.

I hope this helps!

Hi AVare,
yes, it helps. Thanks a lot.

Regards
Hendrik