I just built my first skyline diffuser....

[naethoven]

Hey, Im just learning about diffusor construction so please humor any ignorance I may type : ) But I had a thought, as far as weight issues when building w wood, could you drill out the center of each 2x2 (from the bottom) w a long drill bit, just to get rid of some of the extra weight?

[betserd]

Originally Posted by naethoven

Hey, Im just learning about diffusor construction so please humor any ignorance I may type : ) But I had a thought, as far as weight issues when building w wood, could you drill out the center of each 2x2 (from the bottom) w a long drill bit, just to get rid of some of the extra weight?

Sure, that should not change any of the reflective behaviour of the diffusor. It is a lot of work though, have been thinking about it myself as well and requires a column drill (not sure if that's the right english word). Might even stuff it with rockwool to reduce resonance although that might be overkill, but it never hurts

[naethoven]

OK, here's my next creative thought. If all you really need is for it to be rigid and reflective, in theory would it be ideal to build it out of thick glass? Or, more realistically, atleast somehow overlay the diffusor w glass. That way, you could build it out of foam if you wanted to, then overlay it with 1/4" glass and it would be rigid and reflective, right?


(just don't bump into the corners)

[avare]

Originally Posted by naethoven

OK, here's my next creative thought. If all you really need is for it to be rigid and reflective, in theory would it be ideal to build it out of thick glass? Or, more realistically, atleast somehow overlay the diffusor w glass. That way, you could build it out of foam if you wanted to, then overlay it with 1/4" glass and it would be rigid and reflective, right?

Section 7 of BBC RD 1990-15 covers that and other consruction techniques.

Andre

[naethoven]

ANDRE! Where have you been, sir? I miss picking your brain You may have wondered where I have been as well. I have been working on building the outer shell of my studio.

Anyway, thanks for the link; I'll check that out. Wonderful to see you are still alive!!!!

[Glenn Kuras]

avare!!!!!!!!!!!!!!!!!!!!!!!! Welcome back dude!!!!!!!!!!!!!

[mshayden]

Im going to try making one using 2"x2" foam pieces, instead of wood. (due to weight and cost constrictions).

Any thoughts?

[johndykstra]

Originally Posted by mshayden

Im going to try making one using 2"x2" foam pieces, instead of wood. (due to weight and cost constrictions).

Any thoughts?

Unless you plan to coat the foam with some sort of reflective shell, you are wasting your time. The idea of a diffusor is to reflect, not absorb.

Although this may not be a bad idea... i wish i knew more about resins and epoxys.

[Disjointed]

they do make foam with proper densities for this...

I did some research and found it to be 'red' instead of blue...

I tried to locate it in my area (half-assedly) with no luck..

I think it was a dow product?

there is also a page out there that details how to easily make them out of foam, cutting and using the reverse of the cut as well for a section (but i cannot find the correct link in my bookmarks).

gl

[Nordenstam]

Originally Posted by Tommylicious

Don't know exactly but as you can imagine it weighs quite a lot!

Normal wood is approximately half as dense as water. Water is 1 kg/decimeter^3. With 14.7 meters of 5x5 cm's, it's 1470x5x5/1000/2 -- approx 18 kilos.

Originally Posted by Disjointed

they do make foam with proper densities for this...

I did some research and found it to be 'red' instead of blue...

I tried to locate it in my area (half-assedly) with no luck..

I think it was a dow product?

Dow own the Styrofoam brand. Am building some using the blue sheets. How dense are the red/pink one in comparison? Going to coat it in paint anyway, but, curious minds..

Originally Posted by Disjointed

there is also a page out there that details how to easily make them out of foam, cutting and using the reverse of the cut as well for a section (but i cannot find the correct link in my bookmarks).

Don't! It's a look a like without the benefits of the mathematical design. If you do each section accord to one of the real calculators, you'll be fine though.


Slowly prototyping a styrofoam diffusor now. Used a 6 volt charger and guitar string wired taughtly between two long nails to make a hot knife. The string extends some way past the taught part, making heat adjustment easy by simply clipping onto different parts of the string. A $2 hot cutter! Works fast and fine. Smells like pure death. Needs extreme ventilation! The styrofoam came in 5x60x120cm (~2x24x48 inch) sheets so the hot cutter is used to make 5x5cm (~2x2") beams. If a 60x60 square is desired, the beams can be made slightly asymmetrical, like 4.6x5cm.

The rest of the cuts, every piece given its own unique length, was surprisingly fast and easy to do by hand with a sharp knife. Once I found that the styrofoam cuts better in one direction, that is! :D

..

This calculator: Calculate a Two-Dimensional Primitive Root Diffuser (Skyline) is, IMHO, better than the other one. The other is very coarsly quantized and it drops off one of the rows to make a 12x12 instead of a 13x12 pattern.

Have found some ways to make it easier to use the Oliver Prime calculator:

>Speed of sound:
343 m/s or whatever you want

>Quantize well heights within
Set to 0.001 to check that everything fits. If the rest of the numbers are right, it'll align to any possible quantizer unit desired, like 1mm.

>Lowest frequency:
This is the depth of the diffuser. Take speed of sound as set above, divide by the desired length of the diffusor in meters and divide by two. The prime number in the diffusor is a good starting point. With a 157 long sequence, double that, 31.4cm gives 2mm between each step. Take speed of sound, divide by 0.314 and divide by half = (343/0.314)/2=546.1783Hz.

>Show intermediate results
Not needed if the quantizer is not used.

>Highest frequency:
This sets the well width. It's given by speed of sound/2*100/X where X is well width in centimeters. Ie, to solve for two inch width (2.54cm*2), take 343/2*100/5.08=3375.9842Hz.

>Prime number:
Any prime number you like that adds up to a nice grid.

>Primitive root:
Depends on chosen prime number. Check calculator number two in this link: Section 11.4: Quadratic Residues and Primitive Roots (thanks Gernot! )

># columns: # rows:

Grid must add up to prime number minus one. The limitations on this grid is stated in the first part of the calculator page.


Cheers,

Andreas Nordenstam

[Tom H]

Originally Posted by Lupo

Normal wood is approximately half as dense as water. Water is 1 kg/decimeter^3. With 14.7 meters of 5x5 cm's, it's 1470x5x5/1000/2 -- approx 18 kilos.

Yeah, that seems about right... I'm actually thinking of building a few out of cork in the future.

[Speeddemon]

Tommylicious, I was recommended another link:

Calculate a Two-Dimensional Primitive Root Diffuser (Skyline)

and with your values, their calculations look different. Also, because they use a 13 x 12 grid.

That styrofoam/polysterene stuff; does it work/help at all? And is that stuff available at the Gamma too? (gewoon piepschuim of iets anders?)

[Tom H]

Yes, I guess that's because they use another grid. I think both work.

Originally Posted by Speeddemon

That styrofoam/polysterene stuff; does it work/help at all? And is that stuff available at the Gamma too? (gewoon piepschuim of iets anders?)

I have never built one out of piepschuim, so I am not sure if it works. I do know wood reflects well and is good material for diffusers. So if you're building one you might aswell do it right.

If you decide to use piepschuim stuff, maybe look at tempex, or even better roofmate or floormate. It's denser.

[Schaap]

Originally Posted by Tommylicious

I have never built one out of piepschuim, so I am not sure if it works. I do know wood reflects well and is good material for diffusers. So if you're building one you might aswell do it right.

If you decide to use piepschuim stuff, maybe look at tempex, or even better roofmate or floormate. It's denser.

Wood reflects much better especially in the highs. I've made some wooden 'Skylinetypes' and miniskylines and have the RPG polystyreen one too. Here some pictures of my DIY. If you fill in the PRD-calculator 1110 Hz, 4000 Hz, within .3 cm then you have the dimensions that's been sold a lot

Henk

[dabigfrog]

be very careful using a hot wire to cut the styrofoam... use a fan an much ventilation.
when styrofoam burns you get cyanide gas..... I've been told it does smell like death because it can kill you!

is there a skyline diffuser calculator for a mac?


just my 2 cents

[chatoyant]

hello,


" MHsoft acoustic Calculator "I am looking for this software, the site is down for weeks apparently.


some can send me?

[RKrizman]

[QUOTE=JeffK;3881865]Inspired by Tommy, I'm thinking about building some skyline diffusers as well. As I'm in the US, I'm using 2x2 so some basic conversion was needed of mhsoft's calculations to go from cm to inches.

Based on mhsoft calculations, the column lenghts would be 2", 4", 6" & 8",/QUOTE]

I have a question about your conversion. Correct me if I'm wrong, but a standard 2"x2"
stud is actually 1 1/2" x 1 1/2". Do you have to maintain a correct proportion between the well width and the heights? In other words, should your heights be 1 1/2", 3", 4 1/2" and 6" when converting from the centimeters in the original post?

Thanks,

-R

[RKrizman]

Originally Posted by avare

Section 7 of BBC RD 1990-15 covers that and other consruction techniques.

Andre

Interesting, that document shows construction using square PVC pipes with molded end caps. I suppose it's this sort of thing.....

Furniture Grade Square PVC Pipe & Tube on Available Plastics, Inc.

Anybody try anything like this?

-R

[Lonely Raven]

Originally Posted by RKrizman

Interesting, that document shows construction using square PVC pipes with molded end caps. I suppose it's this sort of thing.....

Furniture Grade Square PVC Pipe & Tube on Available Plastics, Inc.

Anybody try anything like this?

-R

I searched for a long while to find square PVC. Good find! I'm betting it's cost prohibitive though. And there would be some losses in the pits between rounded corners.

I'm still liking the idea of hollowed out wood blocks, or high density styro.

[nextaz]

+1 Please...

thanks

Originally Posted by chatoyant

hello,


" MHsoft acoustic Calculator "I am looking for this software, the site is down for weeks apparently.


some can send me?

[Ethan Winer]

I have the latest version of this calculator, and will gladly send it to anyone who emails me through my web site:

Ethan Winer - Home Page

--Ethan

[chatoyant]

Originally Posted by nextaz

+1 Please...

thanks

is UP !! mh-audio.nl - Home

[Al Nutrition]

Im loving these DIY threads!!!

As the title says, I just built my first skyline diffusers. I made 4 using the same measures as Tom H. Thanks everyone for sharing your knowledge and insight!!! Took a WHILE to make these



Now the question is, how should i use these ?
When I started i was going to put all four, side by side, to the wall behind my listening position in my home studio, to make a 120 cm x 120 cm diffusor. Now that the glue is drying i started to second guess after reading a lot of threads here and started to read the "Master Handbook Of Acoustics by F. Alton Everest & Ken C. Phlmann"

Is there a better way of using these?

Maybe have some distance between the diffusors? One over my 24inch screen to the front wall behind my Dynaudio Bm6a´s and the others to the back wall as 3 in a row, 180 cm x 60 cm?

Here is my room dimensions.

width 3.7
lenght 4.6
height 2.9

I have my listening according to the 38% rule, but the monitoring is facing the 4.6 long wall. Plus the place has no bass traps and only some absorption.

Any suggestions?
I´m just downloading the google sketch to make a model of my room.

[Tom H]

Originally Posted by Al Nutrition

They look great, nice work!

Originally Posted by Al Nutrition

Now the question is, how should i use these ?


Maybe have some distance between the diffusors? One over my 24inch screen to the front wall behind my Dynaudio Bm6a´s and the others to the back wall as 3 in a row, 180 cm x 60 cm?

I have my listening according to the 38% rule, but the monitoring is facing the 4.6 long wall. Plus the place has no bass traps and only some absorption.

Sounds like a good starting point.

I would definitely put some bass trapping in there.

[gordyhaab]

Thank you to everyone on this thread for the very useful info on building a skyline diffuser. Just built one this week, with three panels side by side.

[Lewis.]

Great read this...


I was thinking of another spin off of this design:

In all the wells that are 'O', could you drill a 20mm hole, then build a bass trap into the back of it? This way it would diffuse and absorb the deeper frequencies? May not work but in theory it would be pretty decent

[avare]

Originally Posted by Lewis.

In all the wells that are 'O', could you drill a 20mm hole, then build a bass trap into the back of it? This way it would diffuse and absorb the deeper frequencies?

Yes. I am surprised more people have not done that.

Andre

[Jens Eklund]

Originally Posted by avare

Yes. I am surprised more people have not done that.

Andre

Remembering some of my early ideas I had a couple of years ago:

[johndykstra]

RPG has a design that does this, does it not?

[Lewis.]

I haven't seen one on their page. Wheres the best position to place such diffusors, behind the listener or on the sidewalls? Due to the fact I have limited mounting space (actually none) on my rear wall, I was thinking of having them in moveable stands like one of the other guys on here has done. Then just have them behind my couch behind my head, as the rear if the couch is very low (shoulder high). Would that improve what I'm hearing from the speakers? At present I'm not sitting in the ideal listening spot so I'm getting bass nulls and also some flutter echo.