Quote:
Originally Posted by
Tommylicious
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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.
Quote:
Originally Posted by
Disjointed
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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..
Quote:
Originally Posted by
Disjointed
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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