John Sayers' Design Forum

John Sayers' Recording Studio Design Forum

A World of Experience
Click Here for Information on John's Services
It is currently Mon Mar 08, 2021 7:05 pm

All times are UTC + 10 hours




Post new topic Reply to topic  [ 21 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Flutter Control Angle
PostPosted: Thu Mar 25, 2010 11:50 pm 
Offline
Confused, but not senile yet
User avatar

Joined: Thu Feb 05, 2004 1:56 pm
Posts: 2336
Location: Hanilton, Ontario, Canada
Soundman2020 asked in another thread wrote:
I've been meaning to ask you another question about angles, André: Do you have any idea where the RFZ 6 degree / 12 degree splay angles come from? Any mathematical background on that? I guess there must be, and probably an equation or two to go along with it, but I haven't been able to find much. It just seems to be one of those things that everybody repeats, but nobody gives the underlying reason.


I have never seen any development of RFZ minimum angle criteria. This is understandable considering the wide range of room sizes and geometries.

For flutter control it was empirical. Considering how long it has been since the problem was first addressed, this does not surprise me. Rettinger made reference to 10°* in Acoustics and Noise Control, which is almost 40 years old. Psycho-acoustic knowledge was primitive compared to today.

On a similar vein, do you know how Rettinger's 10° became 12° or where the 12° came from? :?:

Obtusely,
Angular Andre

*Wes' post later in this thread jogged my memory. Michael refered to one in ten splaying, not 10°. Thanks for the memory jog Wes!

_________________
Good studio building is 90% design and 10% construction


Last edited by AVare on Sat Mar 27, 2010 1:55 am, edited 1 time in total.

Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 4:02 am 
Offline
Moderator

Joined: Sat Aug 25, 2007 10:54 am
Posts: 3820
Location: Exit 4, Alabama
Auto Industry Engineers?

_________________
Brien Holcombe
Sound: You can't stop it, you can only try to contain it.


Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 8:22 am 
Offline
Senior Member
User avatar

Joined: Thu Jan 04, 2007 6:37 pm
Posts: 883
Location: Regional Victoria, Aus
Wouldn't the height also be a factor?
To reduse flutter - an 8ft room may need 12degrees but a 10ft room may only need 8degrees.
Sorry I have not read the papers on the subject.
lil

_________________
inkspotproductions
www.bantamstudio.info


Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 9:08 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11938
Location: Santiago, Chile
OK; this is dangerous! Look like I stirred up a hornets nest, and it's going to suck up some more of my time to answer my own question!

And starting to get confusing.

This guy recommends splaying 7% (yes, percent, not degrees, but percent).
http://www.sparling.com/SparAdmin/arts/ ... %20BHJ.pdf

Over here they argue that it is not "12 degrees" but "1 in 12". Then Wes Lachot says that it should actually be 4.7 degrees...
http://recording.org/studio-constructio ... fused.html

Here, someone says that it should be 5 degrees:
http://www.gearslutz.com/board/studio-b ... shape.html


ARRGHHH!!!! Time to study again... Maybe some re-design.....

By the way, there is also an intriguing quote by Eric Desart in one of those threads, saying that it actually is OK to average the dimensions of slightly non-rectangular rooms when calculating ratios and modes, within reason, but understanding that it won't be accurate....

Fun and games! :)


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Last edited by Soundman2020 on Fri Mar 26, 2010 2:21 pm, edited 1 time in total.

Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 9:13 am 
Offline
Moderator

Joined: Sat Aug 25, 2007 10:54 am
Posts: 3820
Location: Exit 4, Alabama
Alton Everest suggested 5%, or more ;)

_________________
Brien Holcombe
Sound: You can't stop it, you can only try to contain it.


Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 12:40 pm 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11938
Location: Santiago, Chile
And this guy at Auralex says anything LESS than 8° or MORE than 15° is "wasting your time"

http://www.acoustics101.com/angled_surfaces.asp


Go figure!

I think I'll just make my walls of Silly Putty, then I can push them around to see what works... :)

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 1:03 pm 
Offline
Moderator

Joined: Sat Aug 25, 2007 10:54 am
Posts: 3820
Location: Exit 4, Alabama
"Before we get into some suggestions there, let us point out that, in many cases you are going to be treating your room(s) with Auralex acoustic products."

For me, that knocks that reference out of the collective.

_________________
Brien Holcombe
Sound: You can't stop it, you can only try to contain it.


Report this post
Top
 Profile  
 
PostPosted: Fri Mar 26, 2010 2:24 pm 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11938
Location: Santiago, Chile
Quote:
For me, that knocks that reference out of the collective.
Yup! Good point. :)

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 12:03 am 
Offline
Confused, but not senile yet
User avatar

Joined: Thu Feb 05, 2004 1:56 pm
Posts: 2336
Location: Hanilton, Ontario, Canada
Soundman2020 wrote:
OK; this is dangerous! Look like I stirred up a hornets nest, and it's going to suck up some more of my time to answer my own question!

I think that part of the problem is that the question is not clearly defined, or at least adhered to. You started with splay angles for RFZ zones. This thread has morphed (incredibly quickly) to eliminating flutter echo. Two distinct, acoustic objectives. Related, but distinct.

Andre

_________________
Good studio building is 90% design and 10% construction


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 12:06 am 
Offline

Joined: Fri Apr 04, 2003 3:31 pm
Posts: 12
Location: Chapel Hill N.C. USA
Soundman2020 wrote:
....
This guy recommends splaying 7% (yes, percent, not degrees, but percent).
http://www.sparling.com/SparAdmin/arts/ ... %20BHJ.pdf

Over here they argue that it is not "12 degrees" but "1 in 12". Then Wes Lachot says that it should actually be 4.7 degrees...
http://recording.org/studio-constructio ... fused.html

Here, someone says that it should be 5 degrees:
http://www.gearslutz.com/board/studio-b ... shape.html
.....
- Stuart -


Stuart,

It depends on what the purpose of the angle is. Some times, you just want the walls to be non-parallel to avoid flutter echoes. Other situations are much more critical, like the side walls of a control room, where you're trying to guide the sound waves in certain directions, to create a reflection free zone. These two examples have almost nothing to do with each other. In the case of flutter echos, 5 degrees is all it takes, and I mean one wall splayed 5 degrees from parallel, not both walls. Just build a room and try it, and you'll see. That's what I did, many years ago. And by the way, it doesn't make a dimes worth of difference whether it's exactly 5 degrees, or a 1/12 slope, which is 4.7 degrees, roughly. (I often express angles as whole number ratios, because it's sometimes easier for builders to get them right when they're communicated that way.)

Control room side walls are a completely different animal, and require much steeper angles, if a reflection free zone is what you're after.

--Wes

_________________
Wes Lachot Design
http://www.weslachot.com


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 12:45 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11938
Location: Santiago, Chile
Thanks, André and Wes! So it's starting to make sense.

To summarize:

General rule of thumb for flutter echo is a 5 degree angle (which is roughly the same as 1 in 12). Wes, is it safe to say that there isn't really a maximum limit angle here, as claimed by one of the websites I linked to, which said that anything over a certain angle (15°) does not work? That doesn't sound right to me.

And the general rule of thumb for Reflection Free Zone, then, is that the angle needs to be calculated for each specific case, based on the speakers, room geometry, etc.

Am I doing fine so far?


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 1:35 am 
Offline
Confused, but not senile yet
User avatar

Joined: Thu Feb 05, 2004 1:56 pm
Posts: 2336
Location: Hanilton, Ontario, Canada
Soundman2020 wrote:
General rule of thumb for flutter echo is a 5 degree angle (which is roughly the same as 1 in 12). Wes, is it safe to say that there isn't really a maximum limit angle here, as claimed by one of the websites I linked to, which said that anything over a certain angle (15°) does not work?

...for Reflection Free Zone, ...the angle needs to be calculated for each specific case, based on the speakers, room geometry, etc.

+2! That's a plus one for both points, summed up excelently.

Andre

_________________
Good studio building is 90% design and 10% construction


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 1:49 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11938
Location: Santiago, Chile
Great! :yahoo: Thanks again; André!

So that leads to the next question: How does one go about calculating the angles for an RFZ? Is this just a matter of sitting down with pen and paper, tracing out rays from the speakers and bouncing them off the room geometry, to see where they go? Or is there a better way to do it? Maybe some software somewhere to help?

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 3:26 am 
Offline
Site Admin
User avatar

Joined: Mon Jan 27, 2003 12:46 pm
Posts: 5456
Location: Australia
I was responsible for the 12 degrees angle back in the Studio Building and Display forum at Homerecording.com back in 2003.

I used 6 degrees in the plans in The Recording Manual back in 98.

Image

When I was building Left Bank in 2000 I had a ceiling where half was at 12 degrees and the other half at 6.

The 6 degrees still produced flutter echoes when you stood under it and clapped your hands so I've used 12 ever since.


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 27, 2010 5:43 am 
Offline
Confused, but not senile yet
User avatar

Joined: Thu Feb 05, 2004 1:56 pm
Posts: 2336
Location: Hanilton, Ontario, Canada
John Sayers wrote:
I was responsible for the 12 degrees angle back in the Studio Building and Display forum at Homerecording.com back in 2003.

When I was building Left Bank in 2000 I had a ceiling where half was at 12 degrees and the other half at 6.

The 6 degrees still produced flutter echoes when you stood under it and clapped your hands so I've used 12 ever since.

Thanks John!

Andre

_________________
Good studio building is 90% design and 10% construction


Report this post
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 21 posts ]  Go to page 1, 2  Next

All times are UTC + 10 hours


Who is online

Users browsing this forum: No registered users and 24 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group