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DIY Diffusors to the Max
Old 8th January 2019
  #511
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Non-EQ-able out-of-phase bass reflections

Quote:
Originally Posted by JayPee View Post
Was re-reading this thread, and may I know how the last measurement looks like? It's old, but, how did you get rid off the 90 HZ and 150 hz dips?

I have exactly the same freq. response right now in my unfinished room.
I never revisited this room. Taking a closer look at the old measurement in ARTAs Unsmoothed DFT frequency response I conclude that it is ±2.2dB below 200Hz given that the Genelec 1032A already rolls off under 45Hz.

To "get rid" of the dips I could have used EQ (personally I prefer not to!) except at ~175Hz because the Excess group delay is quite low: Non-EQ-able out-of-phase bass reflections usually show up as bumps ... most likely the floor reflection in my example (hard to avoid).

BTW: To compare two measurements you have to look at the phase as well!
Attached Thumbnails
DIY Diffusors to the Max-20190108-dft.gif   DIY Diffusors to the Max-20190108-egd.gif  
Old 10th April 2019
  #512
After reading this thread, I have to ask the question: What happened to the room you were working on most of the thread, @ G. E. ?
Old 14th April 2019
  #513
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Moving On

Quote:
Originally Posted by johannburkard View Post
After reading this thread, I have to ask the question: What happened to the room you were working on most of the thread, @ G. E. ?
After I moved both studio and office to a totally new place the old room became more of a production facility and storage space. I'm happy for the time I could stay there and explore room acoustics -- I still use these measurements and findings for new developments.
Old 21st November 2019
  #514
vdH
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Quote:
Originally Posted by G. E. View Post
Basically I've applied Wikipedia information on Maximum length sequence and Chinese remainder theorem to calculate patterns.

As you already showed varying the seed sequence some symmetrical patterns come up (for example with seed 0001111111) while others look "shifted" regarding symmetry. I guess the RPG pattern you mentioned has either another one of the 1023 possible seeds (no 0000000000!) or they shifted the pattern "manually".
Hi G.E.,

Many thanks for sharing all that info. I'll be building one of these in the coming weeks. I'll post pictures of the process and the final results.

I also have a question. Is there anything known about the absorption/diffusion rate? and can it be adjusted by creating more holes to improve the diffusion, or creating less holes to decrease the diffusion. When the given maximum is given then the MLS sequence is a fixed sequence, correct?
Old 2nd June 2020
  #515
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AES e-Brief 612: Deep Diffusorbers

Happy to announce that my Convention e-Brief 612 "Deep Diffusorbers: Real World Application & Scalability of Amplitude Grating Diffusers Covering Ultra-Wideband Absorbers in Small to Medium Sized Venues" is now online and free downloadable from the AES Library.

Abstract: Modern sound systems are capable of reproducing audio at substantial levels down to 20Hz. It is therefore of major interest to control room decay rates down to the lowest octaves even in the most demanding situations. To overcome space requirements and performance limitations of velocity-based absorbers below 80Hz and at the same time provide sufficient diffusion and tailor-made absorption characteristics at mid and high frequencies ultra-wideband diffusorbers have been emerged. Real world application together with before-after measurements of such devices individually constructed of layered amplitude grating diffuser panels, porous absorber elements, and metallic rectangular Kirchhoff plates with free boundaries on resilient sheet show their performance and scalability in a variety of rooms ranging from 900 to 280,000 cubic feet volume.

Kudos to Boggy (who sadly passed away in 2019) who always encouraged/pushed me to publish my work, especially findings incorporating metallic rectangular Kirchhoff plates with free boundaries to the MyRoom Acoustic Design and MyRoom Acoustic Design Mk II concepts he proposed.

BTW, AES Virtual Vienna 2020 Convention hosts additional presentation slides with audio of this engineering brief.
Old 4th August 2020
  #516
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hello, need little help about how to build this kind of panel...
what's the proper name of this diffusor?
I read it called something like "parametric diffusor"...
Is there any guide/calculator app to design it?
I have "tools" to cut and built and would learn some knowledge about how to properly design
Attached Thumbnails
DIY Diffusors to the Max-648753e8cf62dd8dbb2c56cd49485325.jpg  
Old 7th August 2020
  #517
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Diffusor or Not

Quote:
Originally Posted by blackfinder View Post
hello, need little help about how to build this kind of panel...
what's the proper name of this diffusor?
I read it called something like "parametric diffusor"...
Is there any guide/calculator app to design it?
I have "tools" to cut and built and would learn some knowledge about how to properly design
I would not exactly call this an acoustic diffusor because I'm missing a well defined diffusion principle (the math). On the other hand it may well have some diffusing/scattering qualities because of the cliffy surface.

The looks are great though and parametric makes sense with this kind of design making use of software I guess.
Old 4 weeks ago
  #518
Parametric but also periodic.
Old 4 weeks ago
  #519
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Quote:
Originally Posted by johannburkard View Post
Parametric but also periodic.
who can point me to some software/book/formula that i can use to design/calculate that kind of panel ?
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