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First Point of reflection: Diffuse/Absorb
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Nick Di Lorenzo
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4th June 2013
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First Point of reflection: Diffuse/Absorb

The first point of reflection in your set up.

Treat with absorption.
Or
with diffusion?

If so why?
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4th June 2013
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Nick,

Thy shall not treat diffusion with absorbtion, but it's ok to treat absorbtion with diffusion!

Other than that the only rule is: "There are no rules" (as long as you reach your objective, obviously)

Cheers,
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Quote:
Originally Posted by SörenHjalmarsson View Post
Nick,

Thy shall not treat diffusion with absorbtion, but it's ok to treat absorbtion with diffusion!

Ummm... Cheers?
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Quote:
Originally Posted by Nick Di Lorenzo View Post
Ummm... Cheers?
No prob Nick,

I now it might seem confusing and daunting, but you first need to determine your objective viz. your desired response. Once you've done that, you use and implement whatever means and devices necessary in order to achieve said response (exactly what and how depends on your starting point (your room) and the objective (the desired response).

So it's kind of like mixing, except you trust your analyzments more then you do ears (were in mixing you would do the opposite) i.e. It's not quite as subjective as mixing, but almost... Sometimes... :-P

So you see "Absorbtion vs diffusion" is not a legitimate question in and of itself, not without context.

Cheers,
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PS: For the average home studio musician though, i would recommend absorbtion at the primary reflection points every day of the week, why make it more complex than it has to be? If you want to go down the rabbithole then by all means... but don't split hairs when you could be making music!?
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Quote:
Originally Posted by Nick Di Lorenzo View Post
The first point of reflection in your set up.

Treat with absorption.
Or
with diffusion?

If so why?
This is probably most confusing question today in small room acoustics (I'm still not sure why, probably because too much people ignore very specific properties of the small rooms).
First reflections generate non resonant interference in the room, so even if we solve resonant ones (room modes) we will still have problems with notches in our response which doesn't resonate... but ruin our complete impression and make room still technically faulty for serious work.

Non resonant interference is sound waves canceling at the listening place because reflecting boundaries in the room. This is more intensive in the small room because closer proximity of the boundaries than in the larger rooms. This behavior may happen from about 80-500Hz, dependent of loudspeaker position in the room. Some of the problems may be solved with careful loudspeaker/listening place positioning (cancelling cancellations... literally). Very important thing in non-understanding of problems is mostly omnidirectional radiation characteristic from loudspeaker in this range.

Only way to "isolate" our listening impression from faulty mirrored "loudspeakers", because our walls, is absorption, there are NO diffusers which may do this especially because their working range is not at this frequencies... there are no diffusers in small rooms which work below 500Hz... or someone ignore listener proximity problems with phase grating diffusers.

Also, frequency range of problems, and needs for isolation from mirrored images of "loudspeakers" causes fact that absorbers must be large to be effective, usually from floor to ceiling, and 2-4m width... because too large wavelength of frequencies of waves which is cancelled at listening place.

Why we need diffusers at first reflections? We need it to bring back reflections in the rooms above 500Hz, because we naturally need it (people are used to live from their birth, in more reverberant places), or room will sound "too dead" after all "ghost loudspeakers" images are only "deleted" by absorption.
Why diffusion and not only specular reflections? Because diffusers give much better focus (shortly).



So, answer is... following all described above... we need it both, always, in the small rooms. MyRoom Design is logical sequel of this story.

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Maybe front wall absorption, back wall diffusion depending on the size of your space
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Quote:
Originally Posted by boggy View Post
images are only "deleted" by absorption.
Why diffusion and not only specular reflections? Because diffusers give much better focus (shortly).
Cheers boggy, This probably confirmed my choice. Now just to finish sketching up my plans and sending them off to the archi-man.

:D
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Quote:
Originally Posted by Nick Di Lorenzo View Post
Cheers boggy, This probably confirmed my choice. Now just to finish sketching up my plans and sending them off to the archi-man.

:D
I'm not sure if you understand that with notches below 500Hz you cannot get focus even with diffusers. Diffusers are better than flat surface above about 1000Hz in the small rooms, but notches below 500Hz is much more destructive to overall impression... so there is no way to choose one or another if you like to build complete solution


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If you use diffusion in the early reflection points I would study up on how to read a ETC graph and watch it closely. Generally speaking, in a small room, absorption is recommend in these areas. You want to hear what is coming out of the speakers. Not the speakers plus the reflection.
Early or First Reflection Points - GIK Acoustics
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Quote:
Originally Posted by boggy View Post
so there is no way to choose one or another if you like to build complete solution.
Exactly! And excellent points all around, that was what i meant with "absorbtion can go behind diffusion" (if necessary...).

And Boggy is officially taking us down the proverbial rabbithole.............

Cheers,
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Quote:
Originally Posted by SörenHjalmarsson View Post
..........
And Boggy is officially taking us down the proverbial rabbithole.............
..........
Sören, It's small room studio acoustics only, I always trying to take it seriously, or I will be "taken" (very seriously!)... or I probably pay too much for my "lessons"... who knows...



Cheers!

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Quote:
Originally Posted by boggy View Post
I'm not sure if you understand that with notches below 500Hz you cannot get focus even with diffusers. Diffusers are better than flat surface above about 1000Hz in the small rooms, but notches below 500Hz is much more destructive to overall impression... so there is no way to choose one or another if you like to build complete solution
+1. You summed ups as well as possible without writing an essay.

Well summed,
Andre
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Hi

I always prefer diffusion rather than absorption at the first reflection point. There is diffusers that is up for the task without using a inch of porous material. Even down to 200 Hz.

Most of the time I do agree with boggy.

Last edited by Bobecca; 4th June 2013 at 01:44 PM.. Reason: Adding text
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For purposes of mixing and mastering, I think I may steer away from diffusion for first point.
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Quote:
Originally Posted by Bobecca View Post
Hi

I always prefer diffusion rather than absorption at the first reflection point. There is diffusers that is up for the task without using a inch of porous material. Even down to 200 Hz.

Most of the time I do agree with boggy.
Always? How many control/mastering rooms have you actually designed? I find myself curious here...... could you provide some links so we can look at the studios you've designed? I (for one) would love to see them......... I'm sure others would as well......


Rod
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Quote:
Originally Posted by Nick Di Lorenzo View Post
For purposes of mixing and mastering, I think I may steer away from diffusion for first point.


I will say that some 2 channel guys like diffusion on the side walls because of the "effect". At Rock Mountain Audio Fest we did use QRDs in these points and it did indeed sound "cool", but would not recommend it if critical mixing or mastering is involved.
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Quote:
Originally Posted by Bobecca View Post
Hi

I always prefer diffusion rather than absorption at the first reflection point. There is diffusers that is up for the task without using a inch of porous material. Even down to 200 Hz.
Welcome back Bob!

Expanding a bit on Mr Gervaises question, to include the engineering realm of things.... In what way (in your experience) do you find that the translation ability are always superior with diffusion, as opposed to absorbtion, at the primary reflection points? And what aspects of processing do you find becomes more reliable (wrt translation)? Adding and judging the spacial information, dynamics and depth? Transient accuracy? Hight and general Eq judgments? Phantom image impression? Harmonic processing? image and panning decisions? Phase judgements?

It has to be a practical improvement, right? Because you don't need to have diffusion at the primary reflection points in order to have creature comfort.... (or to have an accurate Critical Listening Space IMHO)

Quote:
Originally Posted by Nick Di Lorenzo View Post
For purposes of mixing and mastering, I think I may steer away from diffusion for first point.
Hold on! We haven't even explored the possibility of deflection yet! :-P


/Sören
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Quote:
Originally Posted by Nick Di Lorenzo View Post
The first point of reflection in your set up.

Treat with absorption.
Or
with diffusion?

If so why?
You started with the above general question and then proceeded to write about your room.

What are the dimensions and setup of the room? A very important factor that the rest of the posters have overlooked trying to answer your first question.

Andre
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^^ Yes! It all depends on the nature of your room (and it's interiors) and the desired response...
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Quote:
Originally Posted by Rod Gervais View Post
Always? How many control/mastering rooms have you actually designed?
Rod
Non, the last time I asked that question...
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Originally Posted by adrumdrum View Post
Non, the last time I asked that question...
Well....... if he doesn't actually design (the type of rooms we're discussing at the very least) making statements like "I always" is misleading at best.......

Not that this is anything I find surprising......... just an observation...

Rod
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Hey guys the room is 4.7x4.8 meters.
3m high ceiling

Blank slate.

In early design stages.

Just wondering What will sit best in that first reflection point.
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Quote:
Originally Posted by Nick Di Lorenzo View Post
Hey guys the room is 4.7x4.8 meters.
3m high ceiling

Blank slate.

In early design stages.

Just wondering What will sit best in that first reflection point.
Always use diffusion, the right kind off course.
Nice space BTW. Dont worry that the L*W is the same, easy fix with couple of Helmholtzresonators.

Last edited by Bobecca; 5th June 2013 at 05:37 PM.. Reason: spelling
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Quote:
Originally Posted by Glenn Kuras View Post


I will say that some 2 channel guys like diffusion on the side walls because of the "effect". At Rock Mountain Audio Fest we did use QRDs in these points and it did indeed sound "cool", but would not recommend it if critical mixing or mastering is involved.
What kind of effect do you talk about here. Describe a cool sound?
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Quote:
Originally Posted by Bobecca View Post
Always use diffusion
Making blanket (and unusual) statements like that, without offering any sensible (scientific or testimonial) reasonings or explanations behind, some might call that trolling you know...


Quote:
Originally Posted by Bobecca View Post
What kind of effect do you talk about here. Describe a cool sound?
Mr. Kuras allready described his subjective impression of the effect that the diffusors generated in that particular instance, the word "Cool" is an adjective.... Are you intentionally being dim? If so, that's not very constructive to this thread, or it's progress... And some would even consider such behavior to be a bit trollish aswell... Constructive would be if you actually answered the questions directed at you and offered the OP some explanations to back up your blanket statements!


Cheers,
Sören
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Bobecca,

I am genuinely curious about this, so instead of demanding that Mr. Kuras explains his denotation of the word cool (which should be quite obvious), why don't you explain in what way you've found diffusors to be a superior first reflection point treatment!? Is it that they give you a subjective kick when listening to polished and processed (finished) products i.e. Because they sound 'cool'? Or, is it that they deliver a pleasent creature comfort that you enjoy? Or, is it simply the aesthetics of them that you like? Or, do they deliver practical enhancement i.e. Do they (in your opinion) simplify and short-circuit the mixing process? And if so, in what way? And if so, do you find that translation is more difficult from control rooms where there is absorbtion at the early reflection points?

There is a whole world of difference between listening to allready polished products, as opposed to processing raw material... And it would be nice to know exactly what it is that you are advocating!

Cheers,
Sören
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Quote:
Originally Posted by SörenHjalmarsson View Post
Making blanket (and unusual) statements like that, without offering any sensible (scientific or testimonial) reasonings or explanations behind, some might call that trolling you know...




Mr. Kuras allready described his subjective impression of the effect that the diffusors generated in that particular instance, the word "Cool" is an adjective.... Are you intentionally being dim? If so, that's not very constructive to this thread, or it's progress... And some would even consider such behavior to be a bit trollish aswell... Constructive would be if you actually answered the questions directed at you and offered the OP some explanations to back up your blanket statements!


Cheers,
Sören
Troll cops Sorry I could not resist, but it seems that people get their ego s involved in these threads and it seems Soren that you are looking at the way people formulate their opinions rather then stick to the topic thereby accusing someone of being a troll you become a troll yourself and now I am turning into a troll too

Personally I think the OP needs to get some proper measurements done and take it from there.
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Quote:
Originally Posted by Birdland101 View Post
Troll cops Sorry I could not resist, but it seems that people get their ego s involved in these threads and it seems Soren that you are looking at the way people formulate their opinions rather then stick to the topic thereby accusing someone of being a troll you become a troll yourself and now I am turning into a troll too

Personally I think the OP needs to get some proper measurements done and take it from there.
Wazzup bird,

First of all, i did not accuse anyone of anything, i simply stated that someone might consider his kind of behavior a bit trollish... Not the same...

Secondly, i certainly do not think that your post makes you a troll, on the contrary, it seems to me that you've got some sane values. To be a troll you need to display a persistent behavior... and a troll does not interact with others in a sane or comprehensible fashion...

Thirdly, I might look like a troll =P, but i don't see how being OT could be the same as trolling? I do not make persistent and blanket statments (without explaining myself), i follow along in discussions and try to keep to the subject (where possible =P), i am not deliberately obfuscating, and if you ask me a relevant and direct question i can promise you that i will do my best to answer that question.

If you think that you and i are trolling, then we have a very different understanding of the denotation of that term.

Now back to the intruiging subject of diffusors vs absorbers in the control room, hopefully...

Cheers,
/Sören
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So do you think the OP should get measurements done? What would the best way to do this folks?
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