I suddenly had an idea of making custom panels faster than traditional wooden block diffusors. First printing the surface and filling the empty space in the back with some heady duty foam.
Anyone here tried it yet?
I did a search, but did not find many results, But, I bet it will be popular 10 years from now when more consumers have bigger and affordable printers at home.
https://diy3dprinting.blogspot.com/2013/12/diy-3d-printed-audiophile-sound.html
https://www.3dprintingmedia.network/aectual-launches-mass-customized-3d-printed-acoustic-panels/
Anyone here tried it yet?
I did a search, but did not find many results, But, I bet it will be popular 10 years from now when more consumers have bigger and affordable printers at home.
https://diy3dprinting.blogspot.com/2013/12/diy-3d-printed-audiophile-sound.html
https://www.3dprintingmedia.network/aectual-launches-mass-customized-3d-printed-acoustic-panels/
You could use a skyline diffuser calculator: http://www.mh-audio.nl/Acoustics/DiffusorCalculator3.asp
I'm not sure how accurate it is, but I'd like to see if it's verifiable.
I've looked into this and actually started converting QRDude output to a 3D model. it is a pretty manual process but I was able to at least generate a height map. At some point in the near future I might have time to finish it. I would be happy to provide STLs if someone can print 1m x 1m or so. 
My own printer is about 250mm square, so I'd have to deal with a lot of post-processing.
However, what is even more interesting is the style of panel from this paper: https://www.nature.com/articles/s41598-017-05710-5
Or this one: https://www.researchgate.net/figure...diffuse-scattering-is-achieved_fig1_325798794
I haven't spent enough time looking these over to figure out if we can parametrize the designs of these types of panels to achieve results other than those covered in the papers. It's likely I lack the math skills to do so. However, looking at the example panels in the paper, it should be possible to do legitimate low-frequency diffusion / absorption without 3D printing anything very fancy or difficult.
My own printer is about 250mm square, so I'd have to deal with a lot of post-processing.
However, what is even more interesting is the style of panel from this paper: https://www.nature.com/articles/s41598-017-05710-5
Or this one: https://www.researchgate.net/figure...diffuse-scattering-is-achieved_fig1_325798794
I haven't spent enough time looking these over to figure out if we can parametrize the designs of these types of panels to achieve results other than those covered in the papers. It's likely I lack the math skills to do so. However, looking at the example panels in the paper, it should be possible to do legitimate low-frequency diffusion / absorption without 3D printing anything very fancy or difficult.
The diffusor doesn't need to be solid, so you could get away with probably 5% infill and probably no more than 1.5-2kg of material per square meter. Should be a lot cheaper and a LOT less work than making them out of wood.
The helmholtz design from the nature paper looks especially interesting due to the small form factor, the real challenge, in the case of absorption is avoiding one narrow optimised absorption peak at a specific frequency. I wonder if instead of a set of similar HRs a set of separate optimisation frequencies could be used to get a wideband consistent effect.I've looked into this and actually started converting QRDude output to a 3D model. it is a pretty manual process but I was able to at least generate a height map. At some point in the near future I might have time to finish it. I would be happy to provide STLs if someone can print 1m x 1m or so.
My own printer is about 250mm square, so I'd have to deal with a lot of post-processing.
However, what is even more interesting is the style of panel from this paper: https://www.nature.com/articles/s41598-017-05710-5
Or this one: https://www.researchgate.net/figure...diffuse-scattering-is-achieved_fig1_325798794
I haven't spent enough time looking these over to figure out if we can parametrize the designs of these types of panels to achieve results other than those covered in the papers. It's likely I lack the math skills to do so. However, looking at the example panels in the paper, it should be possible to do legitimate low-frequency diffusion / absorption without 3D printing anything very fancy or difficult.
Nice to see there is interest. I would like to add that for more high end result, of course the backside can also be filled with some more stronger and heavier resin, instead of foam. So turn the thing upside down and just pour it full like a bucket of water.
Just the minimum required for shape should be done with 3D printing, or the material costs go up.
Also, since 3D printing is less labor intensive than making things from wood, I started to think that maybe totally new design for the blocks would be possible. As you know, the max height of the blocks determines how low in frequency it goes and the width of the blocks defines the top end.
What if you would print the bottom of each block normally, but the top of each block you would divide to 4 smaller blocks, each different in height? That would make each individual block stronger compared to really tall and thin blocks, which would be otherwise required for very wide bandwidth.
The average height of those four sub blocks would be the same as the original calculated height of that main block.
I am interested in wide bandwidth, since many commercial foam ones for sale do not offer the dimensions required for that.
Just the minimum required for shape should be done with 3D printing, or the material costs go up.
Also, since 3D printing is less labor intensive than making things from wood, I started to think that maybe totally new design for the blocks would be possible. As you know, the max height of the blocks determines how low in frequency it goes and the width of the blocks defines the top end.
What if you would print the bottom of each block normally, but the top of each block you would divide to 4 smaller blocks, each different in height? That would make each individual block stronger compared to really tall and thin blocks, which would be otherwise required for very wide bandwidth.
The average height of those four sub blocks would be the same as the original calculated height of that main block.
I am interested in wide bandwidth, since many commercial foam ones for sale do not offer the dimensions required for that.
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I don't know if this is necessary. All that's required is that the material is stiff enough to properly reflect frequencies in the range required. I think this is achievable with a hollow 3D print for most frequencies, maybe painting it would help. If you want to get down into the <<500hz range then you might want to fill it with concrete, or resin, or something.
This type of thing has been done, although I think only in "1D" diffusors, they're called "diffractal" and RPG may still have a patent on it. Basically you put higher-frequency diffusors on top of the lower-frequency ones.
I would not necessarily know how to calculate the design for a 2D "diffractal" design. You might need to put a whole 2D QRD on each square? I think they put a whole N=7 QRD on each panel of the 1D design, so that might be it. 4 levels might not be enough, or would only create random scattering / interference above the maximum frequency... but it might raise the plate frequency, which could be desirable even if you don't get "true" HF diffusion...
Anyway, this is doable with 3D printing and probably not even remotely practical with woodworking, so it would be interesting to look into.
Is it possible to calculate without knowing the material!? So, doesn't the type of material never play any role in the diffusion?
Yes-ish, the physical pattern calculated should give a roughly optimised diffusion pattern over a frequency bandwidth. Though diffusion panels are using reflection of the surfaces, so if you were to use a more absorbant material it would still have the same diffusion pattern but less energy is reflected back into the room, and the optimal shape for a diffuser is not that of an absorber. I wonder if a hybrid system would be better, allowing for both some level of each device to get the desired room RT60 and spacial sound benefits.
I have experimented with 3d printing of a qrd diffuser but soon found out that you need a lot of time, it takes too much time, as you need large areas to have useful diffusion. It is also not worth it, in eastern europe you will find companies that make them for a very affordable price nowadays.