SMT Wing Diffusors vs. QRD Diffusors? Effective?

caesar

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May 31, 2010
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Gentlemen, the buzz among acousticians at Axpona was that after spending several hundred thousand dollars on a dedicated room designed by acousticians using traditional products at the Magico factory, and apparently getting bad results, Wolf has slowly been getting more and more SMT products into his room at the factory.
 

Ron Resnick

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Hi all,

Attached you will find a picture of my current room, with my new speakers Rockport Avior and my Mono Totaldac 

View attachment 17821

The room is (only) 22 m² and the acoustic treatment has been a kind of designed by myself after a (very) long time of trial and error and weathering some differences in view with my spouse;).

A period during which I found out that small room acoustics is a real niche within the science of acoustics and at the same time I found that not many acousticians understand the requirements of such dedicated room, actually hardly any of them… reason why I enrolled myself on a 6-month course about acoustics to improve the understanding of the theory behind the practice and start my job as an acoustic consultant.

During the adventure to seek the best design I came across a company on this site whose approach to acoustical problems in small rooms is definitely different from the pack. That company is SMT and I got in touch with its owner Matts Odemalm who has been very helpful in explaining his products and making sure I could hear them in my room.

To cut it short, I was enthralled by his S-wings and V-wings, so much so that, beside my activity as acoustic consultant, I will be holding some stock locally.

This cooperation led to a first result, rather quickly mounted, at the Hi End show in Brussels in October. Through the shop Noir&Blanc, Matts and I were enabled to treat their hi-end room (Rockport Atria / Gryphon Antileon EVO (worldpremiere in non-static display) / Esoteric Grandioso player and DAC) promptly making it the best room of the show (see attached link in French http://voir-et-emouvoir.blogspot.be/2014/10/une-ecoute-exceptionnelle-au-high-end.html?spref=fb) although the acoustic properties of the rooms, as usual at shows hosted in hotels, were far from ideal.

The S-wing is an ideal product to position at the first reflection points bringing more detail, focus and a wider soundstage and above all, a more homogenous frequency respons from the high treble till mid-bass (!!).

The V-wing is very similar in its functioning to the S-wing and is most ideally placed around anywhere basically, behind the listening position (can be up to 30 cms from listening seat), at other reflection points or in front of the front wall (as in previous post). Its time delay function (by about 5 ms) enhances the sense of the recording hall and makes the walls fade away.

Anyway, the next project is to change my room to a level 3 demo room for SMT which should be done by January.
I am aware that I shouln’t add much more to this as this will be read otherwise as a pure sales pitch but I guess the above is interesting to this WBF community that helped me on this path.

Cheers
Michel

Hello from Los Angeles, Michel!

So the wood V-wings mounted on your front wall and side walls serve exactly the same purpose as the clear acrylic things that come on casters and which Jeremy and Greg use in the MBL exhibit rooms at audio shows?
 

Ron Resnick

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Here is my pair of SMT Wings. I put them in the first reflection points:








Hello Elberoth,

What product is behind your listening chair?

If I may ask what is the reason for using the acrylic wings on casters, rather than mounting the wood version on the walls?
 

Ron Resnick

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I just read this entire thread, as was kindly suggested to me by 853guy.

I am very happy for the many satisfied members for whom SMT products have solved their acoustic problems and enhanced their listening pleasure. Similarly, many users of the more traditional RPG Acoustic products, including Andy Payor of Rockport Technologies, apparently are satisfied with RPG products.

It is obvious to me from these testimonials that the products from both SMT and RPG accomplish their objectives, but is there any way to better understand the sonic attributes of these competing products?

Out of curiosity has anyone directly compared SMT V-wings or S-wings with RPG Diffractal or Modfractal products?
 

Calle_jr

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May 24, 2015
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is there any way to better understand the sonic attributes of these competing products?
The SMT Wings are broadband diffussors with very low absorption, but what really differentiate them from other diffussors is that they spread the reflected sound also in time. Not only in space.
The sonic effect is a softer and clearer perception to the ear. The energy is preserved but scattered in space and time.
 

Ron Resnick

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Thank you. How do you decide where to use a V-wing versus an S-wing?

Do the wood versions of the SMT products have greater efficacy than the acrylic versions?
 

Calle_jr

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Thank you. How do you decide where to use a V-wing versus an S-wing?
The V-Wing is deeper (1200x600x250mm) and therefore is effective between 200Hz - 16kHz.
The S-Wing is 1200x600x180mm, and is effective 250Hz - 16kHz.

When using these wings on walls, it's common to tune the volume created between the panels for helmholtz absorption.


Do the wood versions of the SMT products have greater efficacy than the acrylic versions?
No. The acrylic is 300mm deep so it is also effective 200Hz - 16kHz.
I don't like the acrylic for aesthetic reasons, but it is of course more flexible and easier to move and try out the best positions.
 

Ron Resnick

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Thank you. How do you tune an empty space between panels?
 

Calle_jr

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Thank you. How do you tune an empty space between panels?
I'm not sure exactly how SMT or others have done that, but in general it's just to calculate the dimensions of a port to the bass frequency you want it to absorb.
These volumes are usually tuned between 80 and 200 Hz.

So, the concept I guess is to use the Varitune HH boxes for the low bass resonances in the room, and to use the Wings to clean up higher bass frequency resonances.
 

bonzo75

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Hello Elberoth,

What product is behind your listening chair?

If I may ask what is the reason for using the acrylic wings on casters, rather than mounting the wood version on the walls?

So that you can move them around to find the proper position, and then if required mount them
 

bonzo75

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microstrip

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The SMT Wings are broadband diffussors with very low absorption, but what really differentiate them from other diffussors is that they spread the reflected sound also in time. Not only in space.(...)

Do you known of any measurements or simulations that demonstrate this effect?
 

adyc

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Adyc had both

In my opinion, RPG products are superior in diffusion. It really diffuses the sound much better than SMT. People like SMT because of time delays. It will cause reflected sound arrived later than direct sound. It is pleasing and it is similar effect to MBL. It really depends what you want to do with the reflected sound.

SMT wings are very simple to construct. If you are a good carpenter, you can purchase one and make copies of it.
 

Calle_jr

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Do you known of any measurements or simulations that demonstrate this effect?
Both if I remember correctly. Let me look when I get back home to a pc. For sure I have seen a simulation.
In my opinion, it is quite easy to imagine just by looking at the geometry.
 

microstrip

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(...) In my opinion, it is quite easy to imagine just by looking at the geometry.

IMHO we need a lot more than imagination to figure the behavior of sound waves covering three orders of magnitude (2x10E2 to 2E10 Hz) in such structure ... We are not addressing water flow!
 

Ron Resnick

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Jan 25, 2015
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In my opinion, RPG products are superior in diffusion. It really diffuses the sound much better than SMT. People like SMT because of time delays. It will cause reflected sound arrived later than direct sound. It is pleasing and it is similar effect to MBL. It really depends what you want to do with the reflected sound.

. . .

In your experience with both products, is there any logical way to use both products at the same time, trying to realize the best of both products in the same system?

Do you happen to be familiar with the pros and cons of the RPG Diffractal product versus the RPG Modfractal product?
 

Calle_jr

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May 24, 2015
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IMHO we need a lot more than imagination to figure the behavior of sound waves covering three orders of magnitude (2x10E2 to 2E10 Hz) in such structure ... We are not addressing water flow!
By "imagine" I meant visualize. Sorry for bad English.

Here's a simulation of reflected sound on a flat surface:
http://www.hakode.se/wing/Flat-V02-2-Timetrace2-1.mp4

Here's a simulation of the same sound reflected on Flower Wings:
https://m.youtube.com/watch?v=6R0KwhlCK9s
 

Mctwins

Member
Feb 1, 2013
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Great visualization!

It confirms my own and my twin brothers experience how the wings nearfield diffuse field perfect blend with the direct sound.

A similar simulation of fractal diffusers show why they need a distance 2-3 times the lowest diffused wave-lenght.

https://youtu.be/BoV9IyvBi4E

A link from Euphonia (Swedish high end forum ) explain the Forest acoustic theory behind the Wings and why they really shine in small criticall mix rooms.

http://diffusor.com/PDF/170515_Resolution_Mag.pdf


Floyd Toole explain the problems with soft absorbers

Head shadow comb filter effect :
”By any standards, this is a huge spectral distortion, a serious fault because it affects the featured "talent" in most recordings-the person whose picture is on the album cover. Under what circumstances are we likely to hear it as shown here? Obviously, only when the direct sound from the loudspeakers is the dominant sound arriving at the listener's ears. This is the situation in many recording control rooms and custom home theaters, where special care is taken to attenuate early reflections.* ln normally reflective rooms, reflections that arrive from other directions at different times will help to fill in the spectral hole because there will be no acoustical interference associated with those sounds. Therefore, in normally reflective rooms, this will not be as serious as the curve in Figure 9.7d suggests—a fact confirmed by data from Shirley et al. (2007) in the data shown in Figure 9.7c It is a clearly audible effect. Augspurger (I990) describes how easy it is to hear the effect using 1/3-octave bands of pink noise, observing .1 “distinct null at 2 kHz" (p. 177). Pullki (2001) confirmed that the comb filter was the dominant audible coloration in anechoic listening to amplitude-panned virtual images but that it was lessened by roomreflections.”



Sabin absorbers masking effects;

:"Reverberation alone could increase our sensitivity to a medium or low-Q resonance by about 10 dB - a huge effect. This latter fact explains why music is so much more satisfying in a reverberant space than outdoors - timbrally richer because we can hear more of the resonant subtleties. It also explains why the toughest test for loudspeaker accuracy is in a room with some reflections, and why headphones (which have no added reflections) have an inherent advantage, and can sound acceptable when measurements indicate that there really are resonant problems. Killing all early reflections with absorbers not only changes imaging, it also makes loudspeakers with poorly controlled directivity sound better. All interesting stuff for audio folks"

"how do I get rid of the smileys in the link, help!!"
 
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Gene 15352

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Feb 19, 2013
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Anyone recommend the most desirable type of wood when looking at diffusers? Baltic birch, pine, mdf or does it really matter as long as the design is well executed? Thank you.
 

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