cafe67 Posted December 9, 2023 Posted December 9, 2023 quite long and detailed https://hometheaterhifi.com/features/diy/diy-skyline-diffuser-enhancing-acoustic-quality-in-home-theater/ 2 1
playdough Posted December 9, 2023 Posted December 9, 2023 (edited) Quite the undertaking in timber, would be 3 weeks or more full time in putting all that together. Looks like close to 1500 elements. 3D Printing works, but still a big job with 54 hours of print time in each brick. Working on a pattern wall with a couple of different diffuser frequency ranges. One brick at a time. Note, sitting on a 1.3m x 2.2m x 190mm MLV air loaded trap. Edited December 9, 2023 by playdough 2
it is only me Posted February 6, 2024 Posted February 6, 2024 On 09/12/2023 at 6:15 PM, playdough said: 3D Printing works, but still a big job with 54 hours of print time in each brick. Wait what? Is that 54 hours per repeating grid, or is it for an individual block? And, the black caps... are they mini diffusers printed on the top of larger rods/blocks? Do you have a photo with the focus on those? Wow!
playdough Posted February 6, 2024 Posted February 6, 2024 3 hours ago, it is only me said: Wait what? Is that 54 hours per repeating grid, or is it for an individual block? And, the black caps... are they mini diffusers printed on the top of larger rods/blocks? Do you have a photo with the focus on those? Wow! Hi Tim The black caps happened when I ran out of white filament, so finished in some black, surprisingly good result. The internal structure of the plastic print is a spiral helix and I remember about 15% infill on the print, the blocks are finished on a angle. Each brick is around 180 x 190 x 100mm and yes the larger bricks took 54 hours and around 800 grams of filament. I should run off a few more, I need 7 more bricks to finish the job, thy might even end up on the cieling, not sure at this stage.
it is only me Posted February 6, 2024 Posted February 6, 2024 Oh... I had thought you were printing mini skylines on the top of the big skylines. Kind of Multiverse-like. The black does look very cool indeed! Did you download the models or design them yourself? 15% infill... hmmm.... If you could print with no (or wax) infill, would the whole thing be reversible? I.e diffusion on both faces? I don't know why one might want that tho... ? 1
playdough Posted February 6, 2024 Posted February 6, 2024 50 minutes ago, it is only me said: Did you download the models or design them yourself No, found them online after a short search. https://www.thingiverse.com/thing:4073800 Had to scale them slightly to fit my printer bed in the Printer Slicer program, otherwise here we are. 53 minutes ago, it is only me said: 15% infill... hmmm.... If you could print with no (or wax) infill, would the whole thing be reversible? In the Slicer program, I chose 15% infill as I wanted a fairly solid, heavy eventual print. There is no wax or anything, just a 3D print in PLA Filament. A little more information here. 1
almikel Posted April 17, 2024 Posted April 17, 2024 anyone looking to DIY 2D QRD diffusers needs to check out QRDude https://www.subwoofer-builder.com/qrdude.htm QRD (Quadratic Residue Diffuser) designs rely on prime numbers to generate diffusion. If your QRD diffuser has 12 wells (12 is not prime), the best diffusion it can provide is it's lowest prime multiple (ie 3) Primary Root Diffusers (PRD) use different maths, resulting in different well counts. If DIYing, just make sure you're building a diffuser based on good maths/science - not copying a commercial design that may have compromised the science of diffusion to avoid patent issues! Mike 2
almikel Posted April 19, 2024 Posted April 19, 2024 I've been doing some research on PRD diffusers, as I'd come across them in GearSpace, but I'm much more familiar with QRD diffusers... On 18/04/2024 at 1:03 AM, almikel said: Primary Root Diffusers (PRD) use different maths, resulting in different well counts. 1st of all I got my terminology wrong - they're called Primitive Root Diffusers, not Primary.... And prime numbers are still required in the maths of a Primitive Root Diffuser, but PRDs use "Modulo Arithmetic" - which I vaguely remember from uni decades ago, but had to refresh my memory with ChatGPT - Modulo is the remainder left after division... eg 13 modulo 2 = 13/2 = 6 remainder 1 ----> 13 modulo 2 = 1 (just the remainder) eg 14 modulo 2 = 14/2 = 7 remainder 0 ---> 14 modulo 2 = 0 (just the remainder)... ...unfortunately it gets way more complicated to find a Primitive Root of a prime number... ...turns out 2 is a Primary Root of 13, but 3 is not... ...and I'm still not sure in say a 13 well 1D PRD, how 2 as a Primary Root is used in the design of the PRD... ...in QRDs, the residue determines the well depth, I'm still unsure how the primary root is related to well depth in PRDs... ...but cutting to the chase, ideally 2D PRDs are based on prime numbers in each direction (like QRDs), or multiples of prime numbers (eg horizontal 3x5 =15, vertical 2x7=14 for a well count of 15x14=210). I accept I don't understand the maths of PRDs sufficiently, but I suspect a PRD using well counts in each direction like 12 (or 144) will not yield the same diffusion as a PRD diffuser using prime numbers (or multiples of prime numbers) in each direction. I've found a few PRD design calculators on the interweb, unfortunately nothing as sophisticated as Collo's QRDude design tool for QRD diffusers https://www.subwoofer-builder.com/qrdude.htm For 2D QRDs - the pattern should be prime in each direction, and easiest to design/build in a square module (choose your complexity N5, N7, N11, N13, N17 etc), and repeat the pattern to get the size of diffuser you need... Eg an N5 base module repeated 10 times horizontally and 5 vertically Cox and D'Antonio recommend including some "inverse" panels in the mix to reduce lobing, but their alternative is just to rotate a few panels 90 degrees (much easier to build all the panels the same and rotate a few, rather than build different "inverse" panels). QRDude can calculate inverse panels if you want to. On 09/12/2023 at 1:09 PM, cafe67 said: quite long and detailed https://hometheaterhifi.com/features/diy/diy-skyline-diffuser-enhancing-acoustic-quality-in-home-theater/ The effort involved in that build is gobsmacking - I hope the maths behind the design justifies the effort. On 09/12/2023 at 1:09 PM, cafe67 said: https://hometheaterhifi.com/features/diy/diy-skyline-diffuser-enhancing-acoustic-quality-in-home-theater/ I couldn't find any maths or design information in the link provided Mike 1
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