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DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)
Old 6th September 2016 | Show parent
  #691
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Electrisizer ➡️
hello tim, thanks for the answer and your great DIY encourage

wich profiled modulation would you recommend? my back wall is after acustic treatment (absorber) 77cm deep it was the only way to get a good bass treatment in the control room (lenght = 5.60m). now my bass SPL is flat but my room is contracted a not sooo deep diffuser would be preferable, compomising performance vs room size.

my listening position is about 2.50m from absorber treated back wall
Hi Electrisizer. Just about to email you. For anyone else following this, I recommend profiled Modulation 2 if you have the space for it.

Either the original, metric version:
[0 , 8 cm, 10 cm, 6 cm, 10 cm, 8 cm, 0]

Or, for an extra low frequency performance boost, the deeper, imperial version:
[0 , 4 in, 5 in, 3 in, 5 in, 4 in, 0]
Old 6th September 2016 | Show parent
  #692
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🎧 5 years
Quote:
Originally Posted by 0N3 ➡️
This video is amazing!

It is the awesome power and precision of heavy cutting machinery, cuts aluminum like butter. I got bit by this emotion a few years back and ended up buying a lathe and mill and converting them into cnc's, I ended up learning AutoCAD Inventor + Mach3 to control them. Awesome stuff, and you can do amazing things. My two favorite things in life (Writing music and inventing things) both very expensive, but even more so fulfilling.

Sorry* back to the Leanfractals :D
Yes, I predict it's going to become a money sync for me one of these days. Was visiting a friend over the break who specializes in decorative concrete work, and he had managed to snag a CNC for $4000 that had cost the previous owner untold sums ($20k alone spent just upgrading the controllers).

I'll stick to hiring out the CNC work... for now .
Old 7th September 2016 | Show parent
  #693
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Electrisizer's Avatar
 
🎧 15 years
Quote:
Originally Posted by Arqen ➡️
Hi Electrisizer. Just about to email you. For anyone else following this, I recommend profiled Modulation 2 if you have the space for it.

Either the original, metric version:
[0 , 8 cm, 10 cm, 6 cm, 10 cm, 8 cm, 0]

Or, for an extra low frequency performance boost, the deeper, imperial version:
[0 , 4 in, 5 in, 3 in, 5 in, 4 in, 0]
thanks!
im gonna build it soon. i have a lot of larch wood leftover i could use... ill report back.
Old 7th September 2016 | Show parent
  #694
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Electrisizer ➡️
thanks!
im gonna build it soon. i have a lot of larch wood leftover i could use... ill report back.
Awesome. Look forward to hearing how it goes.
Old 17th September 2016
  #695
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Rotaholic's Avatar
 
🎧 10 years
Just wondering if my room would benefit from a diffuser, the room is 12x10 and is heavily trapped in every corner except the floor to wall corners.

The reason I ask is because my best friend makes polystyrene for a living, mostly for chillers and insulation of buildings etc they can make it very very dense. The blocks can be 2 meters squared and up to 10 meters long! What has me interested is that they have a CAD machine that can cut any shape (its a giant hot wire) out of the poly.
All I would need to do is do up a CAD design and hit print.

How would this sound or work? and is it worth while looking in to?
Old 18th September 2016 | Show parent
  #696
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🎧 5 years
Quote:
Originally Posted by Rotaholic ➡️
Just wondering if my room would benefit from a diffuser, the room is 12x10 and is heavily trapped in every corner except the floor to wall corners.

The reason I ask is because my best friend makes polystyrene for a living, mostly for chillers and insulation of buildings etc they can make it very very dense. The blocks can be 2 meters squared and up to 10 meters long! What has me interested is that they have a CAD machine that can cut any shape (its a giant hot wire) out of the poly.
All I would need to do is do up a CAD design and hit print.

How would this sound or work? and is it worth while looking in to?
Hi Rotaholic,

I don't recommend large polystyrene devices as they're a fire hazard in general. Fire resistant polystyrene may be even more hazardous, due to smoke toxicity. If you're going to use a material, make sure it's approved for interior architectural use.

It depends on your room and your goals, but in general a rear wall diffuser would provide benefit if you're sitting in the front portion of the room and the diffuser provides enough reduction to rear wall reflections to meet the reflection free zone criteria.


Before reaching your ears, the European Broadcasting Union criteria is that you want the first reflections to travel at least 17 feet further than the direct sound. Otherwise, you need to treat them so they’re at least 10 dB below the direct sound. Whether or not a diffuser will achieve that in a small room is not simple to predict without measurement, modeling or calculations.

For control rooms I prefer a reduction of 20 dB with diffused reflections delayed by at least 20 ms relative to the direct sound, but in a room this size you're not going to achieve this delay.

You'd instead focus on the achieving the reduction in reflected energy (10 dB absolute minimum), and as much delay as possible.

Since you don't have space for lower frequency diffusion, I would use a diffuser that mainly acts on high frequencies, and mount it over a deep bass absorber on the rear wall. High frequency diffusion can also provide benefit on the front wall and ceiling, but the rear wall is the first place I'd consider.

If you're sitting close to your rear wall, deep broadband absorptive bass traps are a better option here, assuming you will use this room for critical listening.

Hope this helps.
Old 9th October 2016 | Show parent
  #697
Gear Nut
 
Electrisizer's Avatar
 
🎧 15 years
Quote:
Originally Posted by Arqen ➡️
Hi Electrisizer. Just about to email you. For anyone else following this, I recommend profiled Modulation 2 if you have the space for it.

Either the original, metric version:
[0 , 8 cm, 10 cm, 6 cm, 10 cm, 8 cm, 0]

Or, for an extra low frequency performance boost, the deeper, imperial version:
[0 , 4 in, 5 in, 3 in, 5 in, 4 in, 0]

Hello back,
its done

mounted as imperial version. the room was rather dead after treating all the bass away. after installing the diffuser it doesnt feel so claustrophobic anymore. even when talking the diffusive effect is noticable. big thanks for your support

i can take some better photos, when the room is finished. want to illuminate the diffuser
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-fractal.jpg  
Old 10th October 2016 | Show parent
  #698
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🎧 5 years
Quote:
Originally Posted by Electrisizer ➡️
Hello back,
its done

mounted as imperial version. the room was rather dead after treating all the bass away. after installing the diffuser it doesnt feel so claustrophobic anymore. even when talking the diffusive effect is noticable. big thanks for your support

i can take some better photos, when the room is finished. want to illuminate the diffuser
Looks great! I'm glad it improved the spacial impression in your room and I look forward to seeing the end result when the room is finished.

Nice work!
Old 12th October 2016 | Show parent
  #699
Gear Head
 
🎧 5 years
Quote:
Originally Posted by Electrisizer ➡️
Hello back,
its done

mounted as imperial version. the room was rather dead after treating all the bass away. after installing the diffuser it doesnt feel so claustrophobic anymore. even when talking the diffusive effect is noticable. big thanks for your support

i can take some better photos, when the room is finished. want to illuminate the diffuser
Looks great! What method did you use to build the fractal pieces?
Old 12th October 2016 | Show parent
  #700
Gear Head
 
🎧 5 years
I my goal is to diffuse the rear wave of my dipole speakers. They are not planars but rather Linkwitz LX521.

I'm trying to decide between a large Leanfractal array and a large 2D PRD. Immediate benefits of leanfractal:

-Cheaper, but not a huge concern
-MUCH easier to build. Seems like a 2D PRD will take 10 times as long
-Lighter weight
-Perhaps higher bandwidth?
-Less absorption?

However the question of performance comes up since that is the ultimate goal. I want the diffuser to breakup the first reflection, spreading it out over time and direction compared to the otherwise flat wall.

Thoughts?
Old 12th October 2016 | Show parent
  #701
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Electrisizer's Avatar
 
🎧 15 years
Quote:
Originally Posted by Pultzar ➡️
I my goal is to diffuse the rear wave of my dipole speakers. They are not planars but rather Linkwitz LX521.

I'm trying to decide between a large Leanfractal array and a large 2D PRD. Immediate benefits of leanfractal:
do you mean the diffuser will be mounted on the front wall?

i think a leanfractal or any 1d diffuser is better than a 2d PRD if you have a lower ceiling...

ive milled the fractals with a hand milling mashine mounted like this:
Old 13th October 2016 | Show parent
  #702
Gear Head
 
🎧 5 years
Quote:
Originally Posted by Electrisizer ➡️
do you mean the diffuser will be mounted on the front wall?

i think a leanfractal or any 1d diffuser is better than a 2d PRD if you have a lower ceiling...

ive milled the fractals with a hand milling mashine mounted like this:
Yes, these would be on the front wall. The speaker designer recommends this approach but they don't recommend a particular diffuser. Simply that people have preferred diffusion over absorption.
Old 17th October 2016 | Show parent
  #703
Here for the gear
 
🎧 5 years
Smile

Hi everyone,
I'm curious about making an odd kind of diffuser but I don't know if that's possible or not.
I have hundreds of walnut shells and I want to scatter and glue them to a wood surface and then put it on the rear wall.
is it possible or it's a totally bad idea ?
Thanks
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-diff.jpg  
Old 17th October 2016
  #704
Gear Head
 
🎧 5 years
Quote:
Originally Posted by Mojo.Studio ➡️
Hi everyone,
I'm curious about making an odd kind of diffuser but I don't know if that's possible or not.
I have hundreds of walnut shells and I want to scatter and glue them to a wood surface and then put it on the rear wall.
is it possible or it's a totally bad idea ?
Thanks
Seems like that would only diffuse high frequencies at best. You could make a leanfuser and then cover it in nuts perhaps
Old 18th October 2016 | Show parent
  #705
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🎧 5 years
Thanks,
So what is the best type for the rear wall, Fractal or QRD or Skyline?
Old 22nd October 2016 | Show parent
  #706
Gear Addict
 
Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Pultzar ➡️
I my goal is to diffuse the rear wave of my dipole speakers. They are not planars but rather Linkwitz LX521.

I'm trying to decide between a large Leanfractal array and a large 2D PRD. Immediate benefits of leanfractal:

-Cheaper, but not a huge concern
-MUCH easier to build. Seems like a 2D PRD will take 10 times as long
-Lighter weight
-Perhaps higher bandwidth?
-Less absorption?

However the question of performance comes up since that is the ultimate goal. I want the diffuser to breakup the first reflection, spreading it out over time and direction compared to the otherwise flat wall.

Thoughts?

Quote:
Originally Posted by Mojo.Studio ➡️
Thanks,
So what is the best type for the rear wall, Fractal or QRD or Skyline?
Definitely a fractal diffuser array on the rear wall, or a large, complex stepped diffuser. A fractal stepped diffuser, like the Leanfractal, or a fractal QRD diffuser, like the RPG Diffractal are both great choices.

If you're going the DIY route and have the ability to mill the fractal cells (or cut them on a table saw), I recommend the Leanfractal.
Old 7th November 2016 | Show parent
  #707
Gear Head
 
🎧 5 years
Quote:
Originally Posted by hornguy ➡️
Hi Tim
I am thinking of building A1 LF modules to treat the rear wall between the corner bass traps, a width of 4700mm, in addition to front and ceiling reflection points. What depth profile would you recommend without going crazy deep?
In addition for such a large build, which would require a rigid timber to hold the panels in place, I will probably delete the 420 wide rear piece and just use a 90mm wide piece of mdf on either side, relying on 2 or 3 horizontal pieces of timber.

Thanks for the design
I was thinking of doing the same plan here in terms of removing the wide piece on the bottom and using two shorter pieces. Besides the minimal amount of extra work, any downsides to this approach?
Old 7th November 2016 | Show parent
  #708
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Pultzar ➡️
I was thinking of doing the same plan here in terms of removing the wide piece on the bottom and using two shorter pieces. Besides the minimal amount of extra work, any downsides to this approach?
It should be fine as long as long as the diffuser is built to be rigid and you have a good method of mounting it to the wall. French cleat is one of the better mounting methods, and there are numerous ways to incorporate a french cleat into the backside of the panel.

With your modification I can't guarantee your build will be structurally sound, so make sure it's rigid and very strong at the anchor points.

A good approach if the individual modules don't line up with studs is to use Miguel Daje's example of the Leanfuser mounted with french cleat system on rails (PDF download). The rails are fixed to the wall studs and diffuser modules hang off the rails with a French cleat.


Last edited by Arqen; 10th December 2016 at 04:17 AM..
Old 9th November 2016 | Show parent
  #709
Here for the gear
 
🎧 5 years
Quote:
Originally Posted by Arqen ➡️
Definitely a fractal diffuser array on the rear wall, or a large, complex stepped diffuser. A fractal stepped diffuser, like the Leanfractal, or a fractal QRD diffuser, like the RPG Diffractal are both great choices.

If you're going the DIY route and have the ability to mill the fractal cells (or cut them on a table saw), I recommend the Leanfractal.
Thank you so much
Old 9th November 2016 | Show parent
  #710
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🎧 5 years
Smile modern diffusers

Hi again guys,
I've just finished making stepped diffuser for the rear wall and now I want to make some different ones for the side walls.
what is your opinoin about new modern and artistic kinds of diffusers like the pictures below, are they useful or just decorative?
Thanks
Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-5fe87338c89859d571c6a6ede7ac2cb1.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-8f8fa186a449b5d048cd6a4f02c2eeee.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-118118be267db1da8ac8c479b6032132.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-modern-artwork.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-44a140f14a030b9396d523923bb82561.jpg  

Old 15th November 2016 | Show parent
  #711
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ARIEL's Avatar
 
4 Reviews written
🎧 10 years
Quote:
Originally Posted by Schaap ➡️
Thanks Tim for giving this
Today I made a metric diffuser for testing and practising. Found some slats with good dimensions what gives a minimum on sawing.
Basis was a slat of 56mm( 7 x 8mm) and 12 mm height. In the DIY store they saw a MDF bottom 61cm by 38cm(7 x 56mm) and another MDF plate 61 by 28cm( 5 x 56mm) for free.
For the fractals I found a slat 25mm(5 x 5) by 40mm( 5x8mm), so very practical.
The 'difficult' part was to mill manual the 3 and 4 units height in the fractal slat. Need some more practising to get a good result but the photos shows the 'protoype'.

The sound diffuser works great especially when you put the fractals on it.
Looks great ! what is the depth of the fractals that you cut out ? Did you use a Dado blade or a router system ?
Old 16th November 2016 | Show parent
  #712
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🎧 15 years
Quote:
Originally Posted by ARIEL ➡️
Looks great ! what is the depth of the fractals that you cut out ? Did you use a Dado blade or a router system ?
The fractal sequence heights from base there are 4,5,3,5,4. I had a 25mm slat(=5) so I cut out 5 mm(=4)at the sides and 10mm (=3) in the middle.
Used a router. If you DIY with by hand then take the slat a few cm longer because the last cm's most of the time the router won't go 'straight'
Old 17th November 2016 | Show parent
  #713
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Arqen's Avatar
 
🎧 5 years
Quote:
Originally Posted by Mojo.Studio ➡️
Hi again guys,
I've just finished making stepped diffuser for the rear wall and now I want to make some different ones for the side walls.
what is your opinoin about new modern and artistic kinds of diffusers like the pictures below, are they useful or just decorative?
Thanks
They look cool, but a random surface only compares to a diffuser if we're dealing with very large, complex surfaces. The difference is that a diffuser is designed to produce scattering that's as uniform as possible (where the ideal is spreading energy uniformly in both space and time).

Random surfaces are not designed for uniform scattering, but we can look at them statistically. A small random surface with, say, 9 chunks of wood will most likely have a highly nonuniform scattering pattern, while a large random surface with thousands of elements may produce scattering that's statistically as uniform as an optimized diffuser.

At a glance, I think those surfaces you show would be useful as they will scatter sound, but they would not be a replacement for a diffuser of similar size and complexity. I'd avoid them in a critical application like treating first reflection points in a listening environment.

In applications where you don't care about uniform scattering and you just want to complexify the sound field, they would help with that.

Last edited by Arqen; 17th November 2016 at 02:42 AM..
Old 1st December 2016
  #714
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🎧 5 years
I noticed two brands of fractal diffusors on eBay, in various lengths. The US made ones recently went up in price because they are being discontinued (they are primed with latex). I ordered some cheap ones from Latvia, and need to order more! I just wish they were even cheaper. They're crap (excuse the language, but absorb the meaning). They are made from EPS expanded polystyrene beadboard, which is the worst kind of styrofoam material structurally, not even very good for coffee cups. But it is very lightweight and is easily molded in forms. They put beads into a mold with trace amounts of gas and binder, and inject steam, making it pop like popcorn I guess. There is a lot to be learned from the surfboard construction industry. EPS is not nearly as good as extruded polystyrene, much less better plastic foams. But...it is really light! Polyester resins contain styrene and cannot be used on EPS, as it melts the foam. But epoxy can! Shooting chopped fiberglass would lose a lot of detail of the shape, but spraying or brushing epoxy works great on EPS, putting a nice plastic finish on the surface. It's important to treat all sides and the back too, so that it doesn't deform as it sets. The epoxy is available in various thicknesses and setting times, but be careful what you thin it with, to make sure the vehicle is all EPS-safe; alcohol, acetone, xylene are commonly used but would have to be tested. Thinners also significantly weaken the molecular strength unless it all evaporates before the epoxy sets (alcohol causes the most damage, and you have to watch the water content of the alcohol used), so thinned epoxy must be applied in thin layers that allow fast evaporation, and the epoxy chosen should be slow-setting. The thinner (especially alcohol) evaporating can also help cool, giving some additional working time but the cold also decreases the vapor pressure and makes the thinner evaporate too slow. A fan might help. One good part is that epoxy doesn't smell very bad, especially compared to polyester resins; and epoxy is much less dangerous to breathe. Clean-up is usually with alcohol.
Old 1st December 2016 | Show parent
  #715
Here for the gear
 
🎧 5 years
Another possibility would be to scale a fractal design to make boards from 4" thick extruded (not expanded) polystyrene, like the pink or blue extruded insulation foamboard. The material can be rip cut in a table saw and shaped with a dado, or cut with a hotwire if you want to get fancy. Once you have the shaped strips there are several ways to glue panels together. The material is cheap and very light.

Then, much like I described with the beadboard foam, you can put a much nicer epoxy finish on the extruded polystyrene than on the beadboard expanded polystyrene.
Old 1st December 2016
  #716
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🎧 5 years
This epoxy over polystyrene approach has potential for lightweight yet durable 2D skyline and other diffusor designs too IMHO.
Old 3rd December 2016 | Show parent
  #717
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Arqen's Avatar
 
🎧 5 years
Top Acoustics FD-480 Fractal Step Diffuser / Larry Elyea

Quote:
Originally Posted by cyclecamper ➡️
I noticed two brands of fractal diffusors on eBay, in various lengths. The US made ones recently went up in price because they are being discontinued (they are primed with latex). I ordered some cheap ones from Latvia, and need to order more! I just wish they were even cheaper. They're crap (excuse the language, but absorb the meaning). They are made from expanded polystyrene beadboard, which is the worst kind of styrofoam material structurally, not even very good for coffee cups.
Please don't buy that garbage off eBay.

Those are ripoffs of my work, and a fire hazard. The “Top Acoustics FD-480 / FD-240 / FSD-480 Fractal Step Diffuser” is a blatant copy of the Arqen Stepfractal, aka B2-Frac from my thesis.

Ebay removed them a while back, but they’ve popped back up.

Larry Elyea, who runs topacoustics.com and mindseyedigital.net, is the main opportunist peddling these ripoffs. Larry is a fraud. The fact that he's using images that have my name on them, in blurred out print (see images below), is clear evidence that he's stolen my work.

Luckily, many people instantly recognize Top Acoustics / Larry Elyea as a fraud. This is thanks to all of you in the DIY community who have spread the word about these diffusers and respected the Creative Commons License.

And, a special thank you to those who have pointed out Top Acoustics (and other copycats), who are trying to claim ownership of my designs to commercialize them.

Larry is lucky people have been discrete about it to date. I don’t think he understands how large of a following these diffuser designs have (tens of thousands of downloads and growing), and how this may affect his reputation long term.

My original media:



Top Acoustics "FD-480 Fractal Step Diffuser" Ebay page:


Attached Thumbnails
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-ebay-sales-page-topacoustics-fd-480-p1-firefox.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-ebay-sales-page-topacoustics-fd-480-p2.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-ebay-sales-page-topacoustics-fd-480-p3.jpg   DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-ebay-sales-page-topacoustics-fd-480-p3-markup-2b.jpg  

Last edited by Arqen; 3rd December 2016 at 03:45 AM..
Old 6th December 2016 | Show parent
  #718
Here for the gear
 
🎧 5 years
[QUOTE=Arqen;12290876]Please don't buy that garbage off eBay.

Those are ripoffs of my work, and a fire hazard. The “Top Acoustics FD-480 / FD-240 / FSD-480 Fractal Step Diffuser” is a blatant copy of the Arqen Stepfractal, aka B2-Frac from my thesis./QUOTE]

Yes, I love your work and immediately recognized the stolen graphic! I did message him and re said the price had doubled because he wasn't going to make any more after he dumps these. I didn't do business with him.

But I did already order two from the other source, from Latvia, which is also obviously your design stolen. It was gracious of you to share it with us for DIY but for-profit is something else if you don't allow it. JBL used to encourage us to build their enclosure designs for our own use, but it's an entirely different thing to manufacture them for sale.

And like I said, they're real crap, there's no question about that. I wouldn't even consider using them as-delivered. And, manufactured in quantity overseas, they should only cost about $5 before coating with epoxy. The beadboard is the last choice for the worst surfboards too, but it's cheap and light.

I went over a lot of old documents and experiments of people trying to come up with a viable way of making something cheap and light yet functional...RPGs, skyline, and now fractals. I'm convinced that for my home, extruded polystyrene encapsulated on all sides in epoxy would be cheap, light, and functional. Yes, it's not only flammable but it probably gives off nasty fumes when burnt. When I DIY fabric-covered Roxul absorbers I spray them with a formula of 9 parts borax with 4 parts boric acid. That doesn't make it fireproof, it still adds to the fireload of combustibles, but it is not self-sustaining so it won't spread flame rapidly all around your room! Homemade absorbers all around a large room like a church or bar are a fire trap and a real problem for getting the fire department to approve an occupancy permit. I'm not too worried about a few panels on a wall in my home encased in fiberglass, any more than I would worry about hanging the surfboards of identical construction on my walls. Encapsulating it in epoxy changes everything. In a fire, the epoxy is also less toxic than polyester resins. It remains to be seen how this all works out. The styrofoam should only be a lightweight form to build up the epoxy on. But the epoxy will cost more than the polystyrene and weight more. So the more it becomes an epoxy part the better, but it loses the weight and cost advantages that made it attractive in the first place. The essence of the idea is making the correct shape without a lot of mass...it makes the diffusor mostly contain air, a hollow core with a bit of foam to damp its movement.

Of course, ideally, instead of just brushing on epoxy, this should be something more like a layup of frozen pre-prepreg carbon fiber in a mold of the correct shape, then extruded foam core should be pressed in instead of expanded beadboard.

Of course wood is beautiful. But these things could weight 1/20 of what wood ones do, with easier hanging and less chance of injury from falling diffusor panels, and might be ideal for treating some live ceiling areas. Though thinned epoxy with pigment is very self-levelling, without using a mold and without any fabric lay-up it may still look terrible, still obviously beadboard, like putting lipstick on a pig.

And of course I'd need to adhere block panels or strips of appropriate thickness behind successive rows of diffusors too, so that the fractal pattern is repeated on a macro scale in order to be effective at lower frequencies.

Yeah, the guy's a crook trying to sell what he thinks is a finished product if he infringes on your patents.

So what do you think about encapsulating foam, perhaps not polystyrene at all, inside resin, with or without fiberglass or carbon fiber? I'm talking about making panels just like they make the cheapest surfboards. It sure would be light. I don't know how much it would still flex as a diaphragm even when backed with another block of foam in order to stagger the depth of each panel appropriately.
Old 9th December 2016
  #719
Gear Head
 
🎧 10 years
Hi there;

I plan to build (3) 4' tall leanfuser diffusors. I live in the states. In order to make the pieces as smooth as possible Ideally I would get the lumber as close to the necessary dimensions as possibly to minimize cutting.

1) the width of each plateau is supposed to be 60mm or 2 3/8 inches. However I found at my local Lowes they have a large selection of wood pre-cut to a width of exactly .5" by 2.5". I know Tim states that the .5" height works well but what about the 2.5" width? Will this work or is it worth the time to rip these down to 2 3/8" exactly.

2) Also between pine, mahogany, poplar, oak, maple, does any wood type have better diffusion performance than the other?

Thanks so much!
Old 10th December 2016 | Show parent
  #720
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🎧 5 years
[QUOTE=cyclecamper;12296319]
Quote:
Originally Posted by Arqen ➡️
Please don't buy that garbage off eBay.

Those are ripoffs of my work, and a fire hazard. The “Top Acoustics FD-480 / FD-240 / FSD-480 Fractal Step Diffuser” is a blatant copy of the Arqen Stepfractal, aka B2-Frac from my thesis./QUOTE]

Yes, I love your work and immediately recognized the stolen graphic! I did message him and re said the price had doubled because he wasn't going to make any more after he dumps these. I didn't do business with him.

But I did already order two from the other source, from Latvia, which is also obviously your design stolen. It was gracious of you to share it with us for DIY but for-profit is something else if you don't allow it. JBL used to encourage us to build their enclosure designs for our own use, but it's an entirely different thing to manufacture them for sale.

And like I said, they're real crap, there's no question about that. I wouldn't even consider using them as-delivered. And, manufactured in quantity overseas, they should only cost about $5 before coating with epoxy. The beadboard is the last choice for the worst surfboards too, but it's cheap and light.

I went over a lot of old documents and experiments of people trying to come up with a viable way of making something cheap and light yet functional...RPGs, skyline, and now fractals. I'm convinced that for my home, extruded polystyrene encapsulated on all sides in epoxy would be cheap, light, and functional. Yes, it's not only flammable but it probably gives off nasty fumes when burnt. When I DIY fabric-covered Roxul absorbers I spray them with a formula of 9 parts borax with 4 parts boric acid. That doesn't make it fireproof, it still adds to the fireload of combustibles, but it is not self-sustaining so it won't spread flame rapidly all around your room! Homemade absorbers all around a large room like a church or bar are a fire trap and a real problem for getting the fire department to approve an occupancy permit. I'm not too worried about a few panels on a wall in my home encased in fiberglass, any more than I would worry about hanging the surfboards of identical construction on my walls. Encapsulating it in epoxy changes everything. In a fire, the epoxy is also less toxic than polyester resins. It remains to be seen how this all works out. The styrofoam should only be a lightweight form to build up the epoxy on. But the epoxy will cost more than the polystyrene and weight more. So the more it becomes an epoxy part the better, but it loses the weight and cost advantages that made it attractive in the first place. The essence of the idea is making the correct shape without a lot of mass...it makes the diffusor mostly contain air, a hollow core with a bit of foam to damp its movement.

Of course, ideally, instead of just brushing on epoxy, this should be something more like a layup of frozen pre-prepreg carbon fiber in a mold of the correct shape, then extruded foam core should be pressed in instead of expanded beadboard.

Of course wood is beautiful. But these things could weight 1/20 of what wood ones do, with easier hanging and less chance of injury from falling diffusor panels, and might be ideal for treating some live ceiling areas. Though thinned epoxy with pigment is very self-levelling, without using a mold and without any fabric lay-up it may still look terrible, still obviously beadboard, like putting lipstick on a pig.

And of course I'd need to adhere block panels or strips of appropriate thickness behind successive rows of diffusors too, so that the fractal pattern is repeated on a macro scale in order to be effective at lower frequencies.

Yeah, the guy's a crook trying to sell what he thinks is a finished product if he infringes on your patents.

So what do you think about encapsulating foam, perhaps not polystyrene at all, inside resin, with or without fiberglass or carbon fiber? I'm talking about making panels just like they make the cheapest surfboards. It sure would be light. I don't know how much it would still flex as a diaphragm even when backed with another block of foam in order to stagger the depth of each panel appropriately.
Yes, smoke toxicity is actually the biggest issue with those types of materials. I'm not a fan of polystyrene as it relates to sustainability, durability and fire risks, but it's hard to ignore because it's lightweight and easy to form.

Encapsulating it in epoxy would improve the fire properties and greatly increase durability. It sounds like a practical approach.
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