Small program for QRD diffusers (1D & 2D)

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Small program for QRD diffusers (1D & 2D)

Postby Eric.Desart » Wed May 12, 2010 6:27 am

I haven't checked if it is mentioned somewhere in the Forum already.

Accidentally I encountered a link to a site (via a Dutch forum in a post from a member called jaco) from a seemingly clever guy who made a program and entered a lot of additional info about QRD diffusers.
http://www.subwoofer-builder.com/qrd.htm (read also all related help pages)

He clearly states:
Much of the information presented here is an interpretation of the following book:
Acoustic Absorbers and Diffusers: Theory, Design and Application By Trevor Cox, Peter D'Antonio
Google books has a partial display of the book, but for the full story, you will need to obtain your own copy

Understanding the book is very much a work-in-progress, and such, the content of this page, and the capabilities of the QRDude calculator, will change over time.
Hence, if someone has ideas for improvement, this guy seems very open for suggestions.

He made a small program from it:
QRDude calculator downloadable here : http://www.subwoofer-builder.com/qrdude.htm

At a first glance quite an impressive achievement, and I LOVE people giving their sources and a lot of additional links and references.

It's also nice that in addition to lots of good references he didn't forgot to mention two scientists (with link to discussion) in the field:
Ethan from RealTraps and Bryan from GIK talk about QRD's vs Polys

Without joking: this http://www.subwoofer-builder.com site is a nice and valuable site for which my respect.
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Re: Small program for QRD diffusers (1D & 2D)

Postby bert stoltenborg » Wed May 12, 2010 9:00 am

I know I kick in an open door, but I really wonder if QRD's aren't the equivalent of tuned/membrane absorbers in the oaborber world.
So something you better avoid.....
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Re: Small program for QRD diffusers (1D & 2D)

Postby Eric.Desart » Wed May 12, 2010 11:55 am

bert stoltenborg wrote:I know I kick in an open door, but I really wonder if QRD's aren't the equivalent of tuned/membrane absorbers in the oaborber world.
So something you better avoid.....

:wink: I think you kick in de wrong open door! Or the door isn't open yet (in which case it hurts or can hurt).
All former discussions were about the possible 1/4 wavelength resonance (damping) behavior. By calling it a membrane absorber (mass-spring system), you suggest that these wells behave as a Helmholtz resonator (also a mass-spring system).


bert stoltenborg wrote:I have a serious problem with authorataaah....
:mrgreen: Can't you alter this in:
I have a serious problem ....
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Re: Small program for QRD diffusers (1D & 2D)

Postby bert stoltenborg » Wed May 12, 2010 12:08 pm

Maybe we ought to discuss the difussing properties of QRD's and the like.
And define what difussion is intended for.
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Re: Small program for QRD diffusers (1D & 2D)

Postby tonio » Wed May 12, 2010 7:00 pm

bert stoltenborg wrote:Maybe we ought to discuss the difussing properties of QRD's and the like.
And define what difussion is intended for.



Yes , please.
:D
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Re: Small program for QRD diffusers (1D & 2D)

Postby Rod Gervais » Wed May 12, 2010 10:17 pm

Eric,


thanks for the link - this is an excellent resource..........
Rod

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Re: Small program for QRD diffusers (1D & 2D)

Postby bert stoltenborg » Wed May 12, 2010 11:09 pm

Scott, goddammit, please...
:mrgreen: :mrgreen: :mrgreen:
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Re: Small program for QRD diffusers (1D & 2D)

Postby Scott R. Foster » Thu May 13, 2010 3:06 am

Yo bro... I got your back.
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Re: Small program for QRD diffusers (1D & 2D)

Postby Eric.Desart » Thu May 13, 2010 8:08 am

Rod, thanks

Bert, Tonio, I'll expand maybe later.
For the others and as usual, while Bert likes to play the innocent, he has rather clear ideas about this stuff, and, as I understood between the lines, did lots of measurements about diffusers. :) He has his own way of communicating. :roll: Hence we should like to know what Bert knows (but possibly Bert is bounded by some kind of confidentiality).

For me the question isn't that much comparing properties between types, which is extensively discussed here in the forum on several occasions, including all remaining question marks, but when, why, where and if you need addition diffusion whatsoever.
I even do believe that in certain or specific circumstances additional artificial diffusion can be bad (no matter its diffusing quality or properties), worsening an otherwise better room.

Diffusing is a bit like decoupling underneath speakers. A lot see this as some kind of necessity to achieve whatever improvement, even when it's not clear what that improvement should be in the whole picture. It are from these things which seemingly belong to good acoustics, and the more special and/or expensive this looks the better the acoustics will become.
These uncertainties are translated in: "it sounds better", while hardly anyone has the opportunity to make an objective comparison. And in the audiophilie world they love to express unknown things as "subtle differences", where "subtle", not complying with its proper meaning in the dictionary, is standard interpreted/used as "better" or "improvement". "Subtle", not seldom is +/- used as in the fairytale of The Emperor's New Clothes.

The question: "what do these diffusers there in the grand picture of the project at hand" is much too annoying, too abstract, hence it's easier to discuss the qualities or assumed qualities of the objects in themselves, whether these properties contribute to a better room or not. They just belong .....
If a professional simplifies acoustics to its basics (which is more than complicated enough), it doesn't look that professional anymore, and his/hers hourly rate should drop.

Albert Einstein: Everything should be made as simple as possible, but not simpler. Clearly Einstein was no, all too often traditional, audiophile or studio designer.
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Re: Small program for QRD diffusers (1D & 2D)

Postby Scott R. Foster » Thu May 13, 2010 12:09 pm

That's a very nice compilation of information and sources... and impressive work on the calculator.... most impressive.

As to the target of all this well rendered research... well... what Bert knows is something that Eric knows just as well. And that is documented in detail at the site Eric linked - namely that these corrugated surface diffusers are very uneven in their performance per frequency band at the task of diffusion [uniformly scattering incident sound toward all potential angles of reflection regardless of the arriving angle of incidence].

As to the state of the emperor's clothes...

http://www.galaxystudios.com/music/#/st ... laxy_hall/

Those pictures of the Galaxy Studio ceiling speaks a thousand words on the topic, and Bert agrees with those words.
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Re: Small program for QRD diffusers (1D & 2D)

Postby Rod Gervais » Thu May 13, 2010 1:00 pm

Scott,

I will agree with those word as well, but - I will point out that there are very many ways in which to skin a cat.........

At Power Station New York (now Avatar Studios) and New England (Still Power Station) which are both Tony Bonjovi's "A" room - and are world class studios as well, there is no diffusion used.......... these are very large rooms

In studios I have designed (such as Studio "H" Hit Productions in the Philippians and Dark Pine Studios in North Carolina) there is no diffusion used as a part of the design (these are small room studios).

http://www.hitproductions.net/



In Studio H they have had some engineers from both Abby Lane and Air Studios work in their spaces - and they were "blow away" (the Owners communication to me not my words) by the rooms quality and transparency. They had a mastering engineer visit from Munich (that they work with) who said the control room was comparable with his "tweaked" mastering suite. IN terms of acoustics it was not absolutely perfect - flat across the board at the mixing position except for a 3dB boost at 125 and and a 1.5dB dip 80Hz (which they were able to deal with through adjustments using using a Meyer CP Room EQ. The very back of the control room was fairly flat except for the low frequencies - but those were within 3 dB +/- and I don't design for the back of the room - so I am not dissatisfied with those results. Very comfortable listening throughout the room.

this is an email I received from the owner on Sat 8/08/09 4:57 AM:

Hello Rod,

How are you and hope you are doing well. Working now with an engineer
from Air Studios London . . . he was blown away by your room and said
it sounded totally transparent. He said it was one of the best studios
he ever recorded at. When you consider Air was one of the best in the
world that is a great complement. Again congratulations.

Dennis


Although I would not say for a second that diffusion used as a room "treatment" doesn't work - I would have to say that I have not yet encountered a room in which it was necessary to use it as a part of my design.

Sincerely,
Rod

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Re: Small program for QRD diffusers (1D & 2D)

Postby Scott R. Foster » Thu May 13, 2010 1:38 pm

Although I would not say for a second that diffusion used as a room "treatment" doesn't work - I would have to say that I have not yet encountered a room in which it was necessary to use it as a part of my design.


Hi Ya Rod:

I have no bone to pick with your statement - in fact Bert has said as much many times to me and my reply to Bert's similar suggestion that diffusion is generally not nearly as useful as folks assume is that diffusion is a reasonable way to increase the smoothness /modal density of a reverb field without introducing significant additional absorption. A nice tool to have in the bag even if it isn't a component to be assumed necessary. Such an assumption is apparently contradicted by, and Bert's point bolstered by, your experiences in building Class "A" rooms without the use of diffusers - I do not find that surprising in the least. If a guy with plenty of knowledge and experience sets out to design a room without consideration of the use of diffusers - I expect he will get the cat skinned just fine without em.

I merely seek to point out in the midst of a discussion of corrugated diffusers, that if diffusion is desired, the corrugated stuff has flaws that are trivial to avoid, a bent panel will do the job better. If we look in the corner of a certified reverb test chamber, those who consider corrugated diffusers to be the cat's pajamas are in for a surprise - like as not, we will find a bent panel. Or with reference to the pics of the ceiling linked above - that design has stood the test of time and exposure to high talent. I bet Eric picked those units based solely on performance - the fact he probably saved his client an amount greater than his fees by using that style of diffuser versus corrugated units is just gravy.* 8O

*An engineer is a guy who can do for five cents what any damned fool can do for five dollars.

PS: Post pics of those rooms dammit! And make sure the bikini girls are in the shot. We are craven visually oriented creatures us innertoob surfers - cater to our weaknesses! :wink:
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Re: Small program for QRD diffusers (1D & 2D)

Postby Eric.Desart » Thu May 13, 2010 2:10 pm

Scott, Rod,

This is basically a bit what I mean.

Galaxy wouldn't be same without these diffusers, and they are/were integrated in a simulation model.
Rod speaks about that huge "Power Station" New York studio, where part of the diffusion in addition to the shape is integrated in the Helmholtz principle.

And that I personally feel more comfortable with polys Scott, you know as long as you know me.

But in smaller rooms it can well be that you're better without, and certainly with these multi-speaker formats.

Just some oversimplified thoughts:

  • Music started with Mono: Problem a keyhole effect, no or poor localization and no, little or not spacious;
     
  • Then we had stereo: source localization could be introduced, the sound became more spacious. We weren't listening anymore to musical information coming from a point, but listening to music in a 3D space, but still within limits. We could adjust our rooms by absorbing the back (or front), controlling disturbing mirror points and so on. We could fight the disturbing modal behavior in function of 2 speakers nicely located on 1 side of the room.
     
  • Due to the fact this had still some limitations, and whatever we do room acoustics has it limits, we went to 5.1, 7.1, whatever. Basically what we did was what the room couldn't bring substituting by more channels. But at the same time the intervention of this room became more annoying. Some people see 5.1, 7.1 whatever, as an increased number of speakers, but basically good recordings are made as such that they really record in function of these different channels. In fact these speakers substitute what the room couldn't do, and the room itself becomes more disturbing. We also can't treat a room in the same manner as we approached stereo. Those speakers radiate from and towards multiple directions. There is no clear front and backside anymore, no clear left and right (for the music/waves that is).
     
  • Now 3D music will enter the market, and again those recordings are made, or will be made specific for these formats. A bit as a caricature: we better should get rid of the room at all. We are surrounded by speakers, even on top of us (even with a center top speaker).
Last year I was part of extensive listening tests where the same setups were tested in a lot of different rooms, even special hired ones in an hotel, other of the non-environment type and several in between. This were really extensive tests going for > week, with 4 to 5 people and some additional drop-ins.
The idea of diffusion is exactly to smooth everything out which causes localization to diminish. Basically you partly destroy what the multi-channel recording tries to accomplish.

When I made some general comments in this and the previous post, they were meant with relative small rooms in mind (style average volume discussed in fora like this) and traditional home theater volumes and so on.
Hence I can just repeat: Diffusion matters in function of its intended purpose and application and is NOT some standard thing belonging to acoustics as a-non questioned assumed improvement. It is NOT something that inherently improves acoustics, but which have to be seen as a possible contributing part of the acoustics, but as well can be counterproductive.

Hence the first question remains: Do I need additional artificial diffusion and why? What is the purpose? And is it for instance a good idea to substitute absorption at e.g. mirror points by diffusion rather than absorption, or can we better get rid of this disturbance in a more controllable manner?

That one gets crazy in the industry in large rooms with a too high reverberation is in big part that your brain can't identify and localize this noise anymore. Even with an improvement on the diffuse field of -3dB (hardly a difference to speak about if heard on different days) is mainly that diminishing this diffusivity and localizing the noise sources makes it much easier for our brain to handle this disturbing info.

I wrote this fast, hence maybe some nonsense is still included I better didn't wrote.

EDIT May 13: I reformulated some sentences because they didn't express correctly what I had in my mind.
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Re: Small program for QRD diffusers (1D & 2D)

Postby bert stoltenborg » Thu May 13, 2010 2:23 pm

Difussion by numerical theory devices is proposed as a kind of acoustical snake oil by entrepeneur extraordinaire prof. P. and his minions.
It makes rooms bigger, better, faster, whitens your theets and cures fatal diseases, all in one package.

In reality difussion is used in large rooms like concert halls, to try to spread sound smoothly over a large audience.
And with smoothly I mean: don't use a qrd.

Now try to shoot me; I have an A-rated sniper watching my back.

:mrgreen:

(Yo sniper, when are we publishing those damned measurements? :D ).
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Re: Small program for QRD diffusers (1D & 2D)

Postby Scott R. Foster » Thu May 13, 2010 3:17 pm

Like the man said... "Let's do it."

http://en.wikipedia.org/wiki/Gary_Gilmore
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Re: Small program for QRD diffusers (1D & 2D)

Postby Rod Gervais » Thu May 13, 2010 5:08 pm

Eric,

I hope you didn't (even for a second) think that i was suggesting that the poly's used in that room were an afterthought to deal with acoustic anomalies........ I did not (and do not) think that.

I am well aware that they were a part of a very well thought out design.......... that they existed on paper before the "first nail was ever driven".

I never thought of a Helmholtz "trap" as adding any real degree of diffusion, rather i thought this they were strictly resonators. To what degree do they add diffusion?

I understand completely about the particular geometric configuration of the rooms at Power Station - Tony and I spent quite a long time discussing this, the rooms at both Dark Pine and Hit Productions are based on the same principles - and with this I understand that we are creating a diffuse sound field - but again - I did not think of this in the "conventional" terms of using diffusion within the space.

It appears I have to rethink my use of the term.......

Thanks (once again) for opening my eyes........

Your friend,
Last edited by Rod Gervais on Thu May 13, 2010 5:47 pm, edited 1 time in total.
Rod

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Re: Small program for QRD diffusers (1D & 2D)

Postby Rod Gervais » Thu May 13, 2010 5:23 pm

DSC_3377.jpg
Hit Productions, string and main rooms
(254.16 KiB) Not downloaded yet




DSC_3412.jpg
Hot Productions, main room
(260.65 KiB) Not downloaded yet



DSC_3361.jpg
Hit Productions - Control Room
(244.84 KiB) Not downloaded yet
Last edited by Rod Gervais on Thu May 13, 2010 5:40 pm, edited 1 time in total.
Rod

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Re: Small program for QRD diffusers (1D & 2D)

Postby Rod Gervais » Thu May 13, 2010 5:38 pm

img_0646.jpg
Dark Pine Studios - Control Room
(55 KiB) Not downloaded yet



img_0695.jpg
Dark Pine Studios - Main Room
(56.45 KiB) Not downloaded yet



img_0664.jpg
Dark Pine Studios - Main Room
(59.33 KiB) Not downloaded yet
Rod

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Re: Small program for QRD diffusers (1D & 2D)

Postby Scott R. Foster » Thu May 13, 2010 7:20 pm

nice...
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Re: Small program for QRD diffusers (1D & 2D)

Postby bert stoltenborg » Thu May 13, 2010 7:37 pm

I hope these axes in the control room have hair bands round the neck....
Handy for damping the strings in case of advanced tapping AND mixing!

:mrgreen:
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