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DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)
Old 7th September 2015 | Show parent
  #631
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Sonic_X ➡️
Another question if you don't mind Tim
My space is limited, behind my chair is only 2,26m till the back wall where I wanted to install Leanfractal. Is there any sense of using 3 module with profiled modulation or 5 module with profiled modulation is also safe to use?
Yes, you should be safe using either version (I recommend the 5-module if you have space). Lots of people have used these diffusers closer than recommended without noticing problems.

If you're striving to create a critical listening room with a long initial signal delay gap (search this forum for ISD gap if you don't know what that is) then broadband absorption is the most predictable way to tame that rear wall reflection. But fractal diffusers are way cooler and will let you treat the rear wall without over-absorbing the high frequencies in your room.
Old 10th September 2015 | Show parent
  #632
Gear Maniac
 
Sonic_X's Avatar
 
🎧 10 years
Thumbs up

Quote:
Originally Posted by Arqen ➡️
Yes, you should be safe using either version (I recommend the 5-module if you have space). Lots of people have used these diffusers closer than recommended without noticing problems.

If you're striving to create a critical listening room with a long initial signal delay gap (search this forum for ISD gap if you don't know what that is) then broadband absorption is the most predictable way to tame that rear wall reflection. But fractal diffusers are way cooler and will let you treat the rear wall without over-absorbing the high frequencies in your room.
Great! Thank You Tim
Gonna go for the 5 module then!
Cheers
Old 11th September 2015
  #633
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🎧 5 years
Glad to hear. Hope it serves you well and I look forward to seeing the photos!
Old 27th December 2015
  #634
Gear Head
 
🎧 5 years
Hello!

I just finished reading all posts in this thread and the documentation that was emailed to me by Tim. I'm really excited to have found this!

There is a wall in my theater that is 18' 3" wide which I want to treat with diffusion. This wall is about 13' from the listening position. Previously to finding this thread my plan was to either:

a) Build several QRDs with 1.5" well width and 8" max depth. I'm afraid this will be a bit daunting but I'm willing to take it on.
b) Purchase RPG Diffractal units to cover the wall. This will be very expensive but probably give me better results than my own QRDs. Not to mention easier

Now I am considering the covering of the wall with a fractal stepped diffuser. Easier to build than QRD and much cheaper than RPG Diffractal.

If I go with the lean fractal design I should be able to fit 13 units on the wall. At this point am I better off going for custom designed higher order panels to increase performance?
Old 3rd January 2016
  #635
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Popeydope's Avatar
What a good informational thread!! Thanx!
I will start next week....
Old 7th January 2016 | Show parent
  #636
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Pultzar ➡️
Hello!

I just finished reading all posts in this thread and the documentation that was emailed to me by Tim. I'm really excited to have found this!

There is a wall in my theater that is 18' 3" wide which I want to treat with diffusion. This wall is about 13' from the listening position. Previously to finding this thread my plan was to either:

a) Build several QRDs with 1.5" well width and 8" max depth. I'm afraid this will be a bit daunting but I'm willing to take it on.
b) Purchase RPG Diffractal units to cover the wall. This will be very expensive but probably give me better results than my own QRDs. Not to mention easier

Now I am considering the covering of the wall with a fractal stepped diffuser. Easier to build than QRD and much cheaper than RPG Diffractal.

If I go with the lean fractal design I should be able to fit 13 units on the wall. At this point am I better off going for custom designed higher order panels to increase performance?
Hi Pultzar,

Glad you found this useful! For most people I don't think the Leanfractal is easier to build than QRDs, unless you have an easy way to mill the fractal cells (they are generally very time consuming to do). But there is a performance advantage over a standard QRD, and most people greatly prefer the look.

Also, you need to consider the mounting method for both the Leanfuser and Leanfractal, since each panel should be mounted at a specific depth. This may be the most challenging part of the build.

If I were you I'd go with either the Leanfractal, RPG Diffractal or RPG Modfractal.

If you have the time and ability to do the Leanfractal, it will be a rewarding project. If you decide to go this route shoot me an email and I can give you information about the mounting system I'm currently working on, which can be adapted to 13 panels. Some of this info I don't share online as there have attempts by other companies to commercialize my designs under their own name.

Otherwise, the RPG Diffractal (or newer Modfractal) are excellent choices. If you're in North America you can actually get the RPG product line through me, and I can get you a good price. Everything is built to order by RPG with your choice of finish.

I should add a note about this in one of my emails as most people don't have the time/tools/skills to do their own fractal diffuser build.

Cheers,
Tim
Old 7th January 2016 | Show parent
  #637
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Popeydope ➡️
What a good informational thread!! Thanx!
I will start next week....
Glad you like it! Hope the build goes well and feel free to share any trials, tribulations or photos with us.
Old 8th January 2016 | Show parent
  #638
Gear Head
 
🎧 5 years
Quote:
Originally Posted by Arqen ➡️
Hi Pultzar,

Glad you found this useful! For most people I don't think the Leanfractal is easier to build than QRDs, unless you have an easy way to mill the fractal cells (they are generally very time consuming to do). But there is a performance advantage over a standard QRD, and most people greatly prefer the look.

Also, you need to consider the mounting method for both the Leanfuser and Leanfractal, since each panel should be mounted at a specific depth. This may be the most challenging part of the build.

If I were you I'd go with either the Leanfractal, RPG Diffractal or RPG Modfractal.

If you have the time and ability to do the Leanfractal, it will be a rewarding project. If you decide to go this route shoot me an email and I can give you information about the mounting system I'm currently working on, which can be adapted to 13 panels. Some of this info I don't share online as there have attempts by other companies to commercialize my designs under their own name.

Otherwise, the RPG Diffractal (or newer Modfractal) are excellent choices. If you're in North America you can actually get the RPG product line through me, and I can get you a good price. Everything is built to order by RPG with your choice of finish.

I should add a note about this in one of my emails as most people don't have the time/tools/skills to do their own fractal diffuser build.

Cheers,
Tim
Thanks Tim, I have sent you an email.
Old 9th January 2016 | Show parent
  #639
Gear Head
 
🎧 5 years
Quote:
Originally Posted by Popeydope ➡️
What a good informational thread!! Thanx!
I will start next week....
Which configuration do you plan on building?
Old 9th January 2016 | Show parent
  #640
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Popeydope's Avatar
Quote:
Originally Posted by Pultzar ➡️
Which configuration do you plan on building?
Not sure yet.
Old 9th January 2016 | Show parent
  #641
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Popeydope's Avatar
Quote:
Originally Posted by Arqen ➡️
Glad you like it! Hope the build goes well and feel free to share any trials, tribulations or photos with us.
Of course I will.
Old 19th February 2016
  #642
Here for the gear
 
🎧 5 years
Hi. I wanted to see if anyone could simulate the leanfuser using well depth .75 inch (19mm) and 2.5 inch width (63.5mm) . This is readily available 1 x 3 wood stock. I need to build diffusers asap but have no access to a table saw and shop for now. I saw that deeper wells could have a positive affect on performance and 3.5 mm wider width is not too much more. Can a simulation be run for me for the 7 unit array with the 0,8,10,6,10,8,0 height setup. Thanks !
Old 19th February 2016
  #643
Here for the gear
 
🎧 5 years
Hi Tim. I wanted to also say that my studio is a Mac based computing system.. So I can't run the reflex software. Please let me know what you think about my proposed .75 inch well depth and 2.5 inch width. Thanks
Old 22nd February 2016 | Show parent
  #644
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🎧 5 years
AFMG Reflex on Mac

Quote:
Originally Posted by alchematic ➡️
Hi. I wanted to see if anyone could simulate the leanfuser using well depth .75 inch (19mm) and 2.5 inch width (63.5mm) . This is readily available 1 x 3 wood stock. I need to build diffusers asap but have no access to a table saw and shop for now. I saw that deeper wells could have a positive affect on performance and 3.5 mm wider width is not too much more. Can a simulation be run for me for the 7 unit array with the 0,8,10,6,10,8,0 height setup. Thanks !
Hi Alchematic,

That changes the depth:width ratio significantly so it's definitely worth simulating, but my time is taken up by some demanding projects and I don't have Reflex installed right now. I'll need to upgrade my license when the time comes to do more tests I have planned (focused on fractal diffusers).

Bear in mind that most people here used the 30 day trial version, so chances are their trial has expired.

You could install Windows in Boot Camp (I believe you can use Windows for a few weeks without a license) and then install the Reflex demo. It would be worth the time to know the diffusion performance before you build the array, and the knowledge could be useful to others as well.

Let us know if you decide to try this out.

Cheers,

Tim
Old 22nd February 2016
  #645
Here for the gear
 
🎧 5 years
This thread is gold. I'll be making a leanfractal soon.
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-img_20150730_181056.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-img_20160111_221955.jpg  
Old 22nd February 2016 | Show parent
  #646
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🎧 5 years
Quote:
Originally Posted by John the Lion ➡️
This thread is gold. I'll be making a leanfractal soon.
Awesome, John. I dig your room and it would be great to see photos when the Leanfractal is done!
Old 24th February 2016 | Show parent
  #647
Here for the gear
 
🎧 5 years
Thanks for the reply Tim. I am having trouble getting the reflex software to load and work. Sadly I don't have a lot of time to mess with it. I am really hoping that someone here can run the simulation for me. Both my studio and a small film stage need diffusers built asap and I was hoping to build with the stock boards instead of having to hire out for a contractor to rip 1/2 inch plywood. So.. Anyone! Can you run a simulation for me? 19 mm well depth and 63 mm width in a series of 7 units.
Old 27th February 2016 | Show parent
  #648
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by alchematic ➡️
Thanks for the reply Tim. I am having trouble getting the reflex software to load and work. Sadly I don't have a lot of time to mess with it. I am really hoping that someone here can run the simulation for me. Both my studio and a small film stage need diffusers built asap and I was hoping to build with the stock boards instead of having to hire out for a contractor to rip 1/2 inch plywood. So.. Anyone! Can you run a simulation for me? 19 mm well depth and 63 mm width in a series of 7 units.
Hi Alchematic,

The general trend when depth increases is positive, so I think you'd be fine acoustically, but it's very far off from the original and it will be heavy. Draw it out to visualize it before building it, as it will be a lot deeper than the original. My question is... why not use 1/2" MFD or plywood and get it cut at the lumber store? It makes more sense to me than stacking a bunch of 1x3s which will require much more material and will be very heavy.

I've attached the closest example I could find. Ugnlenol tried dramatically increasing the depth:width ratio by decreasing the well width to only 35 mm, and the results for a 7 panel array are shown in the 1st attachment below. But bear in mind that with 63 mm wells your high frequency performance won't be like this, and in this example the profiled modulation depth was also scaled, not just the panel depths.

For reference, the 2nd attachment shows 35 mm well widths, while keeping roughly the original proportions. And the 3rd attachment has the same depths as the 2nd, but with 30 mm wells, representing a 1.17x increase in the depth:width ratio.

All these diffusion coefficients are plotted up to 8 kHz.

Your diffuser would be closer to the first image if you scaled the profiled modulations as well as the panel depths. But I suggest you don't scale up the profiled modulations.

Looking at just the panels, you would have a 1.84x depth:width ratio increase when compared to the imperial version of the Leanfuser (where the imperial version assumes 1/2" (12.7mm) MDF for unit of depth, with total width of each panel being 16").

In your situation I would see how much it would be to get 1/2" MDF or plywood cut in-store, and if it's not expensive, make the imperial Leanfuser (it's explained in the FAQ here, but for clarity I will create plans for it in the future).

Cheers,
Tim
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-unglenol-35mm-well-width_-12mm-ply_-0453540_mod-seq-x-3.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-unglenol-35mm-well-width_-6mm-ply_-0453540_mod-seq-x-3.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-unglenol-30mm-well-width_-6mm-ply_-0453540_mod-seq-x-3-150cm-wide-array-.jpg  

Last edited by Arqen; 27th February 2016 at 07:19 AM..
Old 9th April 2016
  #649
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andre tchmil's Avatar
 
🎧 15 years
I have the space on my back wall to mount 4 pieces of B2-FRAC units.
Should I leave out a step where the modules are joining ?
Or how to calculate the pattern ?
Old 10th April 2016 | Show parent
  #650
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by andre tchmil ➡️
I have the space on my back wall to mount 4 pieces of B2-FRAC units.
Should I leave out a step where the modules are joining ?
Or how to calculate the pattern ?
Hi Andre,

Use [1 0 1 1] as the modulation sequence. Other aperiodic MLS sequences of length 4 would work too, like [1 0 0 1], but I recommend [1 0 1 1] as it's closer to the original 5-unit sequence.

The 0 just represents a diffuser module that has been flipped, so it's a mirror image of the others.

Let me know how it goes if you build these.
Old 23rd April 2016
  #651
Gear Head
 
🎧 5 years
I have been working some experiments and models for a 13 unit wide array. What do you think of these simulations? Does anyone stand out as superior? I'm going to do a different model per post to keep things organized.
Old 23rd April 2016
  #652
Gear Head
 
🎧 5 years
Model2
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model2-outline.png   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model2-plot.png  
Old 23rd April 2016
  #653
Gear Head
 
🎧 5 years
Model4 (there is no Model3)
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model4-outline.png   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model4-plot.png  
Old 23rd April 2016
  #654
Gear Head
 
🎧 5 years
Model5
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model5-plot.png   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model5-outline.png  
Old 23rd April 2016
  #655
Gear Head
 
🎧 5 years
Model6
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model6-outline.png   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-model6-plot.png  
Old 23rd April 2016
  #656
Gear Head
 
🎧 5 years
Assuming that the simulation is accurate, the dividers seem to increase low frequency performance. Model4 does better in the high end while Model6 is better at the low end.
Old 23rd April 2016 | Show parent
  #657
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🎧 5 years
Quote:
Originally Posted by Pultzar ➡️
Assuming that the simulation is accurate, the dividers seem to increase low frequency performance. Model4 does better in the high end while Model6 is better at the low end.
Hi Scott,

Great work and thanks for sharing! These are nice results.

Model 4 has the best overall performance, while Model 6 has the best lower frequency performance.

The 13 panel suggestion I originally gave (Model 5) is based on a 7 panel modulation flanked by two 3 panel modulations, but better performance can be found using a purpose-designed 13 panel modulation, like your Model 2 or 4.

You're right that the dividers increase low frequency performance here. This is useful knowledge for someone who needs low frequency diffusion, but people need to be aware of the increased listening distance (and room size) required when diffusing lower frequencies.

Also, people should not generalize this to all stepped diffusers. In The optimization of profiled diffusers, Trevor Cox found optimized stepped diffusers without fins had higher performance, and these findings may hold true for stepped diffusers optimized for low frequency performance.

The original Leanfuser shape was optimized to give efficient mid frequency diffusion (mid and high with the Leanfractal), with simple, modular, form-follows-function geometry, at a listening distance of 2.5 meters. At 2.5 meters efficient spatial scattering is important, while low frequency diffusion is less of an asset and more of a liability that can result in audible artifacts.

Here's a visualization of what I mean by efficient spatial scattering. This video shows a time domain simulation of a single Leanfuser panel, and I thought it was cool how you can see the optimized shape sending a bunch of energy sideways immediately after impact.


The Leanfuser is designed to create spatial diffusion directly, where a finned diffuser is designed to create temporal diffusion, which also results in spatial diffusion. I've not seen studies on this but I expect finned designs take a bit more space to produce spatial diffusion, because the fins channel the sound waves before letting them spatially disperse.

The diffusion coefficient used by Reflex uses a listener radius of 5 meters, which is the measurement standard, but most people end up using their diffusers closer than this.

Thanks again for doing these experiments and sharing your useful findings! Any of these 13 panel designs would be good, and I'm sure there are other great combinations out there.

P.S. I should be candid that I'm biased toward finless and have a habit of personifying diffusers. Sometimes I view finned diffusers like control freaks who are trying to micromanage and domesticate the sound wave, before releasing it . I view finless as more natural surfaces that say "just bounce off me like the wild sound wave you are, and you'll scatter".

Finless have an intuitive form-follows-function look that many people find gives aesthetic appeal (these do hang on walls, after all). E.g., last week a lass who knew nothing about acoustics correctly guessed that the weird thing in my office was designed for scattering sound, and also thought it looked like abstract art.

Of course there are still advantages to finned diffusers and I have the highest respect for Schroeder, who invented them. They are easy to design, and the fins can be used as structural elements that may make it easier to vary the mounting depth. Also, a new finned design doesn't require new construction methods -- it can simply be build using the standard QRD construction methods.
Old 23rd April 2016 | Show parent
  #658
Gear Nut
 
🎧 5 years
Here's a very simple and DIY friendly design with good performance:

Making easy DIY "Depot" sound Diffuser panels, step by step - diyAudio
Old 23rd April 2016
  #659
Gear Head
 
🎧 5 years
Thanks for your analysis Tim!

I am going to be sitting around 12 feet from these diffusers and they won't be visible to me (painted black in a dark theater) so I'm not worried about how they look.

That being said I don't know if the finned designs are better for me or not. As you say they may affect the spatial dispersion. Also we aren't seeing absorption coefficients here. I'm assuming that a fin-less design probably absorbs less?
Old 23rd April 2016 | Show parent
  #660
Gear Head
 
🎧 5 years
Quote:
Originally Posted by seiyafan ➡️
Here's a very simple and DIY friendly design with good performance:

Making easy DIY "Depot" sound Diffuser panels, step by step - diyAudio
Thanks for sharing! I think I'll model these in a wider array with some depth modulation.
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