good discussion
I still think tho that John doesnt use QRD diffusors maybe for a matter of taste or just school. He is free to use them on large rooms but he rather not
All good anyway! Just a different approach
Is diffusion dead?
Originally posted at johnlsayers.com, topic 13591.
maybe it's that I once worked in a studio designed around diffusion and hated it :)
BTW - I do find Ethan's diffusers interesting as he only attempts to diffuse the high end (the studio I worked in tried to do the low end unsuccessfully)
well
you have been putting it all the time just in another form
Another form of diffuse surface is the ‘amplitude reflexion grating’, an example of which is shown in Figure 4.33. In fact, any juxtaposition of absorbent and reflective surfaces will cause sound to scatter due to the steering of the wavefront as a result of phase changes at the boundary. There are also mathematical procedures for the optimum relative positioning of absorbent materials to promote diffusion,5 such as binary and prime number sequences. Amplitude reflexion gratings tend to diffuse not so well as the physically deeper diffusers, but they take up little depth, and the depth does not limit their low frequency performance. (page 112 recording studio desing, Newell)
A diffuser needs to break up the reflected wavefront. While this can be achieved by shaping a surface, it can also be done by changing the impedance of the surface. Indeed, Schroeder diffusers are often interpreted as being a surface with a spatially-varying impedance. In this chapter, variable impedance is achieved by patches of absorption and reflection. Unlike the Schroeder diffuser, these cannot be designed for minimum absorption. These surfaces are hybrids somewhere between pure absorbers and nonabsorbing diffusers. Partial absorption is inherent in the design while any reflected sound is dispersed. Acoustic Absorbers and Diffusers,p373 , Trevor J. Cox, Peter D’Antonio
Whats that mastering studio with just diffusers all over the room?
George Massenburg's Blackbird Studio. Photo below. More coolness here: http://www.youtube.com/watch?v=UdOsXOkli98 --EthanWhats that mastering studio with just diffusers all over the room?
External image, not preserved — original: http://www.ethanwiner.com/misc-content/gml.jpg
That looks very cool. thanks Ethan
A couple of questions for you..
What do you think about tha design?
Do you think there is some kind of bass treatment behind the diffusers? Like basstraps on the wall behind the diffusers
And the last one, those diffusers are randomly? or there is some formula to cut the woods....
I have seen that room a couple of times and every time it takes away my breath...
if it works or not, it LOOKS fantastic! man!
The wall diffusers are 3 feet thick. The ceiling diffusors are 7 feet deep. No absorbers behind them. There are corner absorbers which are an evolution of poly diffusors. Curved BAD panels explicitly.Do you think there is some kind of bass treatment behind the diffusers? Like basstraps on the wall behind the diffusers
They are based on equations. The wall diffusors are based on modulo 953 with a 181 by 769 array. The ceiling diffusors are based on modulo 157 with a 12 by 13 array. AndreAnd the last one, those diffusers are randomly? or there is some formula to cut the woods....
I never heard it so I can't even guess.What do you think about tha design?
I thought I once read that there are bass traps behind the diffusors, but Andre says No. Maybe it's just that with so much diffusion of that design, there's a lot of bass trapping as a side effect. I honestly don't know. --EthanDo you think there is some kind of bass treatment behind the diffusers? Like basstraps on the wall behind the diffusers
Here is the source, pdf page 8. http://www.rpginc.com/news/seminars/Diffuse_Seminar_2007_iRoom.pdfI thought I once read that there are bass traps behind the diffusors, but Andre says No.
It is not so much a side effect as a totally forgotten part of the acoustics of diffusers that all have significant amounts of absorption. With the dimensions of those diffusors, absorption is going to be significant down to low frequencies. Which is ignoring what the wall structure is and its low frequency absorption. Absorbingly, AndreMaybe it's just that with so much diffusion of that design, there's a lot of bass trapping as a side effect.
Well, that's what I meant. :mrgreen: Are you going to AES again this year? If so, please stop by the RealTraps booth and say Hi. I'll be there Friday and Saturday, then again Monday to chair the Audio Myths workshop. --EthanIt is not so much a side effect as a totally forgotten part of the acoustics of diffusers that all have significant amounts of absorption.
Unfortunately no. Have fun with the seminar and I hope you have diffusively absorbing time. AndreAre you going to AES again this year?
Thanks, I don't expect much more than minor grumbling from the golden ears types. :o --EthanI hope you have diffusively absorbing time.
:) ( André, if you ever quit the audio/acoustics industry, then you have a very promising future as a comedian! ) - Stuart -... hope you have diffusively absorbing time.
Thanks guys, very informative.
Difussion is obviously more expensive, that why most people go the other way i guess
My take on this: diffusion is definitely useful in small rooms, as our video (Ethan linked above) demonstrates. However, diffusion is rarely cost-effective. Bass trapping and reflection point absorption is much more important. Diffusors are expensive to build (very labor-intensive). If you have the budget for them, they are great, but don't add diffusors at the expense of bass trapping and reflection control.
"diffusion is definitely useful in small rooms,"
I think you guys should help folks out and define >your< interpretation of a small room.
I think it is...skirting a thin marketing line to continue to say these types of things when in fact the real traps video your stuff Mr Winer says " I am not a fan of diffusion at reflection points, at least not in small rooms, in rooms 16 foot wide, etc. etc. etc".!
Generally by "small room" I mean anything under 2500 cubic feet as a general rule of thumb.
I agree, diffusion is rarely useful at reflection points. However, they are very useful in a small room at other places, such as the rear wall. In our video: http://www.realtraps.com/video_hearing.htm
We use bass traps in corners, high frequency absorption at reflection points, and diffusors everywhere else. The result speaks for itself.
Please elaborate more diffusion is rarely useful at reflection points And i do not agree in just putting high frequency absorption at reflection points while this will keep you from localizing the reflections since you are only absorbing the the high freq you will still be receiving the first reflection of the low freq and that will change the spectral balance of what you hear if you are going to use an absorber to eliminate first reflections you better use enough thickness to at least the transition point that for small rooms should be around 300hz (3" to 4"absorber)Generally by "small room" I mean anything under 2500 cubic feet as a general rule of thumb. I agree, diffusion is rarely useful at reflection points. However, they are very useful in a small room at other places, such as the rear wall. We use bass traps in corners, high frequency absorption at reflection points, and diffusors everywhere else. The result speaks for itself.
Hi Valentin,
Perhaps I should have said, in my experience I have always preferred absorption to diffusion at first-reflection points. It makes more sense to me to just eliminate the reflection energy entirely, rather than diffusing it (which keeps the energy in the room, just scattered).
By high-frequency absorption, I mean a panel that is effective down to 300Hz or so. Remember, bass is essentially omnidirectional in small rooms, so it's very difficult to tell where bass is coming from. For reflection points, it's not necessary to absorb well into bass frequencies.
For instance, our MicroTraps are 1" thick and are effective down to about 300Hz. This is more than enough absorption, assuming there is good bass trapping elsewhere in the room. If you want even more absorption, then of course you can use thicker panels and gain some benefit.
JWL addressed your other question, but I can comment on this:
I agree that all absorbers should be as thick as possible. Generally, the more bass traps you have, the better the response and ringing. But early reflections are mainly a mid/high frequency issue, which is what "imaging" and "sound stage" are mostly about. Another issue is it's best to put bass traps where they'll do the most good, unless we're talking about a million dollar control room. The side-wall reflection points usually receive less bass build-up than the corners, and the front and rear walls. --Ethanyou will still be receiving the first reflection of the low freq and that will change the spectral balance of what you hear
Ethan
but mixing is not just about imaging and sound stage there are the tonal and spectral qualities if you use thin absorption you will be changing the spectral balance at the mixing position jwlI agree that all absorbers should be as thick as possible. Generally, the more bass traps you have, the better the response and ringing. But early reflections are mainly a mid/high frequency issue, which is what "imaging" and "sound stage" are mostly about.
normal speakers radiate bass omni directionality, bass in small room are more affected by the modal response omni directionality does not mean you cannot localize the source localization is more frequency dependant effectbass is essentially omnidirectional in small rooms
what is efective Example 2" fiberglass 3lb/p 125hz 0.40 250hz 0.73 500hz 1.14 1000hz 1.13 2000hz 1.06 4000hz1.10our MicroTraps are 1" thick and are effective down to about 300Hz
reflections of the right type are not as bad as their fame states :D
Ethan
time back i sent you this papper
here are some word from Tomlinson Holman (THX) page32 Sourund Sound second edition
Dr Floyd Toole book Sound reproduction is highly recommended and it go in deep about side reflectionsA different view of some of these specifications is held by a prominent researcher Dr. Floyd Toole. In his paper “Loudspeakers and Rooms for Sound Reproduction—A Scientific Review,” AESJ, Vol. 54, No. 6, pp. 451– 476, he argues for the benefits of early reflections, among many other things. Since this work is relatively new, it has not been absorbed into standards yet. However, I can state that in my experience we do adapt to a stronger set of early reflections in one room versus another, because among other places I work in a space designed in the early 1980s that exhibits strong early reflections. Upon entering the space, especially from listening in a more reflection controlled space, I find the timbral signature of comb filtering obvious, yet within a few minutes I adapt to this space and can perform program equalization about as well as in the deader space. A cinema that employs diffuse early reflections at a higher level than normal from the side walls has been built in Europe, and enjoys a good reputation. While staying within the maximum reverberation time set by the THX standards that I wrote, this cinema shows that there may be an advantage to diffuse side wall reflections.
Yes, I'm aware of Floyd Toole's position. I have compared this many times in my own two listening rooms, and in the rooms of many customers. I disagree that first reflections sound good. Certainly they badly skew the response. Maybe early reflection are okay in a very large room, like 30 feet wide or wider. I'm not rich enough to have a living room that large. :) And the reflections won't be "early" at those distances anyway.
Floyd's own research supports the view that flat speakers sound better universally than speakers that are not flat. Since it's easy to prove how badly skewed the response can be when early reflections are not absorbed, Floyd's two positions seem contradictory. :|
Whatever. It's pointless to argue over subjective stuff like "sounds better" or "sounds worse" so I don't even try. All I care about is what can be proven, and it's not difficult to prove that early reflections harm the response. If some people like that effect, I won't say they shouldn't. Any more than I'd tell a hi-fi listener not to dial in a smiley faced EQ curve if he thinks that sounds better.
--Ethan
that's what you see not necessarily what you hear he also states that not all early reflections are goodCertainly they badly skew the response
If something can be proven is the work of Dr. Floyd and its all stated in his book and on the several contributions and papers of many acoustistian around the world Remember not because you can measure something it means it correct or not correct microphones do not discriminate and your Brain doesAll I care about is what can be proven
i think you need to read the book again, your mixing ideas indead flat and smooth anecoic response on axis with smooth and constant change in directivity are found to be preferd this is Anecoicaly mesurments (Very important) this way reflections in the room will have neutral spectral balace that will reinforce and in some intances smooth things out (like the phantom stereodip) and other aberrations of boundery efects etc. etc. there is no souch contradition what you see in some type of mesurments does not show the whole pictureFloyd's own research supports the view that flat speakers sound better universally than speakers that are not flat. Since it's easy to prove how badly skewed the response can be when early reflections are not absorbed, Floyd's two positions seem contradictory.