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DIY Binary Amplitude Diffuser anyone?
Old 28th December 2015
  #91
Lives for gear
 
jhbrandt's Avatar
Adhoc,

Ha! You're probably right. :D
Cheers,
John
Old 28th June 2016
  #92
I like the look of the Newell secuence on binary diffusers, i find the consistance of the gaps and slats prety apealling. But still dont like the repetition of the secuence.

Is it a bad idea to use a dice to introduce randomness in the gapings and slats of that secuence?

Ex. A 8 sided dice to determine the slats (1 = 1" 2=2" and so on) and a 4 sided dice fir the gaps.

This way we would modulate randomnly the gaps and the slats, and using diferent dices we would alter the % of absorption of the surfaces. been 75% reflection in the example

Tell me what you think
Old 28th June 2016
  #93
Lives for gear
 
boggy's Avatar
Quote:
Originally Posted by Sebastian Vera View Post
....
Tell me what you think
It's a good idea:



Old 28th June 2016
  #94
Hahaha i did not wanted to reveal the inspiration....
Old 29th June 2016
  #95
Gear Maniac
 
robertopisa's Avatar
What do you mean by random? With dice, you could get always the same number. I think some spreading properties on diffusion would be better, which are obtained by a deterministic rule rather than a random one.

-R


Quote:
Originally Posted by Sebastian Vera View Post
I like the look of the Newell secuence on binary diffusers, i find the consistance of the gaps and slats prety apealling. But still dont like the repetition of the secuence.

Is it a bad idea to use a dice to introduce randomness in the gapings and slats of that secuence?

Ex. A 8 sided dice to determine the slats (1 = 1" 2=2" and so on) and a 4 sided dice fir the gaps.

This way we would modulate randomnly the gaps and the slats, and using diferent dices we would alter the % of absorption of the surfaces. been 75% reflection in the example

Tell me what you think
Old 30th June 2016
  #96
We are not searching for spesific difusión. Randomness is needed to avoid any patern. Periodic secuences will reduce the performance of the system.
Old 1st July 2016
  #97
Gear Maniac
 
robertopisa's Avatar
Random, meant as tossing dice, can have periodic patterns for short sequences

If you are using a long sequence of tosses, the sequence is approaching what we want. However, for small sequences, IMHO it is better to use a deterministic rule that avoids repetitive patterns internally. To make a concrete example: with 10 or 20 slabs, I would not use random choice using dice, but I would use MLS; with 100 or more slabs, random would make sense to me.

Cheers
-Roberto

Quote:
Originally Posted by Sebastian Vera View Post
We are not searching for spesific difusión. Randomness is needed to avoid any patern. Periodic secuences will reduce the performance of the system.

Last edited by robertopisa; 1st July 2016 at 01:18 PM.. Reason: adding more comments
Old 1st July 2016
  #98
The idea is to use more than 100, we would probably talk about 400 for an entery tracking room of small size. As boggy pic shows there would be 1000 slats in there

A small panel some where in the room is prety useless. We talk about full cover

And sorry but probabilities of findig a patern of more than 10 slats repeated in a secuence of 8 random variables is near 0
For ex. Rolling a dice and 6 times having a 1 all the times has a ptobability of 0,002%
Old 1st July 2016
  #99
Gear Maniac
 
robertopisa's Avatar
Regarding the probability of 0,002%, this is true if you repeat many times the experiment. (It's probably OT, but if you are interested in these topics, you can give a look at the Kolmogorov complexity, where random strings are those that cannot be represented as significantly shorter strings. This definition does not use dice and is more robust.)

Since you use many slabs, then the above is no more an issue. If it helps, you can look at some good generators for random numbers in

https://www.random.org

Cheers
-Roberto

Quote:
Originally Posted by Sebastian Vera View Post
The idea is to use more than 100, we would probably talk about 400 for an entery tracking room of small size. As boggy pic shows there would be 1000 slats in there

A small panel some where in the room is prety useless. We talk about full cover

And sorry but probabilities of findig a patern of more than 10 slats repeated in a secuence of 8 random variables is near 0
For ex. Rolling a dice and 6 times having a 1 all the times has a ptobability of 0,002%
Old 1st July 2016
  #100
Exelent! Will look at it
Old 4th September 2016
  #101
Gear Head
 

Hello,
I would love to use MLS (specifically the sequence posted by Boggy) to create amplitude diffusion in my control room.
I have read through the whole thread by am still a bit confused... I am afraid i am not a mathematician. I have a feeling that there are quite a lot of base assumptions regarding putting the sequence into practice that goes over the layman's head!
- I am assuming the width of the slats determines the diffuser's effectiveness at low frequencies?
- are the "zeros" in the sequence representative of a gap, the same width as the chosen slats?
- Which part of the sequence should i choose if i do not require that many slats? Do i start at the beginning? don't the number of "1's" and "0's" need to be equal?
-using answer from question above, can i use that sequence repeatedly if i just want to cover many separate 2' by 4' broadband absorbers (that are not flush together) or should i continue where the last sequence ended?

Any help would be most useful and gladly received
Old 18th November 2016
  #102
Quote:
Originally Posted by mole-man View Post
- I am assuming the width of the slats determines the diffuser's effectiveness at low frequencies?
The width of the slats is like a cut off freq. The wider the slats the low you can "reflect"

Quote:
Originally Posted by mole-man View Post
- are the "zeros" in the sequence representative of a gap, the same width as the slats?
yes

Quote:
Originally Posted by mole-man View Post
- Which part of the sequence should i choose if i do not require that many slats? Do i start at the beginning? don't the number of "1's" and "0's" need to be equal?
Where ever you like. In theory this secuence has the same amount of 0 and 1. In short secuence you can see that there is a concentratuon of 1 or 0 but in a larger scale this evens out

QUOTE=mole-man;12114205]
-using answer from question above, can i use that sequence repeatedly if i just want to cover many separate 2' by 4' broadband absorbers (that are not flush together) or should i continue where the last sequence ended?[/QUOTE]

You should continue. This secuence is about avoiding periodicity
Old 18th November 2016
  #103
Gear Maniac
 
robertopisa's Avatar
I would use a single huge sequence. Here we are talking of 1D sequences but I tested that putting together two 2D sequences is not giving a good result in terms of low autocorrelation. Informally, low autocorrelation says that if you overlap the sequence with one shifted copy, there exist few aligned 0s and 1s (so most of the cases you find aligned 0 1 or 1 0, and rarely 1 1 or 0 0). This probably applies to 1d sequences too.

That said, symmetry is also important (e.g. left and right wall can be specular) but in principle you could use a single long sequence spread along all the walls.

Quote:
Originally Posted by mole-man View Post
-using answer from question above, can i use that sequence repeatedly if i just want to cover many separate 2' by 4' broadband absorbers (that are not flush together) or should i continue where the last sequence ended?

Last edited by robertopisa; 18th November 2016 at 05:46 PM.. Reason: typos
Old 15th April 2018
  #104
Gear Head
 

Quote:
Originally Posted by boggy View Post
DanDan ask me to post binary sequence on Gearslutz forum in thread REW Analysis, then, instead of starting a new thread, I'll use this old one that has a nice explanation of binary diffusers functioning (thanks to jayfrigo ), for posting a part of MLS pseudorandom sequence.

Here are a first 127 members of pseudorandom sequence (MLS) that may be used for building binary diffusers. I hope that this is enough for most applications. If someone need more, please ask, and we will generate more...

Sequence:

Code:
position:126 ***** 1
position:125 ***** 0
position:124 ***** 0
position:123 ***** 0
position:122 ***** 0
position:121 ***** 0
position:120 ***** 0
position:119 ***** 1
position:118 ***** 0
position:117 ***** 0
position:116 ***** 0
position:115 ***** 0
position:114 ***** 0
position:113 ***** 1
position:112 ***** 1
position:111 ***** 0
position:110 ***** 0
position:109 ***** 0
position:108 ***** 0
position:107 ***** 1
position:106 ***** 0
position:105 ***** 1
position:104 ***** 0
position:103 ***** 0
position:102 ***** 0
position:101 ***** 1
position:100 ***** 1
position:099 ***** 1
position:098 ***** 1
position:097 ***** 0
position:096 ***** 0
position:095 ***** 1
position:094 ***** 0
position:093 ***** 0
position:092 ***** 0
position:091 ***** 1
position:090 ***** 0
position:089 ***** 1
position:088 ***** 1
position:087 ***** 0
position:086 ***** 0
position:085 ***** 1
position:084 ***** 1
position:083 ***** 1
position:082 ***** 0
position:081 ***** 1
position:080 ***** 0
position:079 ***** 1
position:078 ***** 0
position:077 ***** 0
position:076 ***** 1
position:075 ***** 1
position:074 ***** 1
position:073 ***** 1
position:072 ***** 1
position:071 ***** 0
position:070 ***** 1
position:069 ***** 0
position:068 ***** 0
position:067 ***** 0
position:066 ***** 0
position:065 ***** 1
position:064 ***** 1
position:063 ***** 1
position:062 ***** 0
position:061 ***** 0
position:060 ***** 0
position:059 ***** 1
position:058 ***** 0
position:057 ***** 0
position:056 ***** 1
position:055 ***** 0
position:054 ***** 0
position:053 ***** 1
position:052 ***** 1
position:051 ***** 0
position:050 ***** 1
position:049 ***** 1
position:048 ***** 0
position:047 ***** 1
position:046 ***** 0
position:045 ***** 1
position:044 ***** 1
position:043 ***** 0
position:042 ***** 1
position:041 ***** 1
position:040 ***** 1
position:039 ***** 1
position:038 ***** 0
position:037 ***** 1
position:036 ***** 1
position:035 ***** 0
position:034 ***** 0
position:033 ***** 0
position:032 ***** 1
position:031 ***** 1
position:030 ***** 0
position:029 ***** 1
position:028 ***** 0
position:027 ***** 0
position:026 ***** 1
position:025 ***** 0
position:024 ***** 1
position:023 ***** 1
position:022 ***** 1
position:021 ***** 0
position:020 ***** 1
position:019 ***** 1
position:018 ***** 1
position:017 ***** 0
position:016 ***** 0
position:015 ***** 1
position:014 ***** 1
position:013 ***** 0
position:012 ***** 0
position:011 ***** 1
position:010 ***** 0
position:009 ***** 1
position:008 ***** 0
position:007 ***** 1
position:006 ***** 0
position:005 ***** 1
position:004 ***** 1
position:003 ***** 1
position:002 ***** 1
position:001 ***** 1
position:000 ***** 1


here are some examples:









Good luck!

Boggy
Hello Mr. Petrovic!

Can you please give me the longer sequence? I use narrow wooden slats in my room and that's why the 127 positions are unfortunately not enough for the whole room (or the half of the room). I would have to repeat parts of the sequence ...

That would be very nice and helpful.

Thank you and best regards
Matthew
Old 15th April 2018
  #105
Gear Head
 

Quote:
Originally Posted by boggy View Post
DanDan ask me to post binary sequence on Gearslutz forum in thread REW Analysis, then, instead of starting a new thread, I'll use this old one that has a nice explanation of binary diffusers functioning (thanks to jayfrigo ), for posting a part of MLS pseudorandom sequence.

Here are a first 127 members of pseudorandom sequence (MLS) that may be used for building binary diffusers. I hope that this is enough for most applications. If someone need more, please ask, and we will generate more...

Sequence:

Code:
position:126 ***** 1
position:125 ***** 0
position:124 ***** 0
position:123 ***** 0
position:122 ***** 0
position:121 ***** 0
position:120 ***** 0
position:119 ***** 1
position:118 ***** 0
position:117 ***** 0
position:116 ***** 0
position:115 ***** 0
position:114 ***** 0
position:113 ***** 1
position:112 ***** 1
position:111 ***** 0
position:110 ***** 0
position:109 ***** 0
position:108 ***** 0
position:107 ***** 1
position:106 ***** 0
position:105 ***** 1
position:104 ***** 0
position:103 ***** 0
position:102 ***** 0
position:101 ***** 1
position:100 ***** 1
position:099 ***** 1
position:098 ***** 1
position:097 ***** 0
position:096 ***** 0
position:095 ***** 1
position:094 ***** 0
position:093 ***** 0
position:092 ***** 0
position:091 ***** 1
position:090 ***** 0
position:089 ***** 1
position:088 ***** 1
position:087 ***** 0
position:086 ***** 0
position:085 ***** 1
position:084 ***** 1
position:083 ***** 1
position:082 ***** 0
position:081 ***** 1
position:080 ***** 0
position:079 ***** 1
position:078 ***** 0
position:077 ***** 0
position:076 ***** 1
position:075 ***** 1
position:074 ***** 1
position:073 ***** 1
position:072 ***** 1
position:071 ***** 0
position:070 ***** 1
position:069 ***** 0
position:068 ***** 0
position:067 ***** 0
position:066 ***** 0
position:065 ***** 1
position:064 ***** 1
position:063 ***** 1
position:062 ***** 0
position:061 ***** 0
position:060 ***** 0
position:059 ***** 1
position:058 ***** 0
position:057 ***** 0
position:056 ***** 1
position:055 ***** 0
position:054 ***** 0
position:053 ***** 1
position:052 ***** 1
position:051 ***** 0
position:050 ***** 1
position:049 ***** 1
position:048 ***** 0
position:047 ***** 1
position:046 ***** 0
position:045 ***** 1
position:044 ***** 1
position:043 ***** 0
position:042 ***** 1
position:041 ***** 1
position:040 ***** 1
position:039 ***** 1
position:038 ***** 0
position:037 ***** 1
position:036 ***** 1
position:035 ***** 0
position:034 ***** 0
position:033 ***** 0
position:032 ***** 1
position:031 ***** 1
position:030 ***** 0
position:029 ***** 1
position:028 ***** 0
position:027 ***** 0
position:026 ***** 1
position:025 ***** 0
position:024 ***** 1
position:023 ***** 1
position:022 ***** 1
position:021 ***** 0
position:020 ***** 1
position:019 ***** 1
position:018 ***** 1
position:017 ***** 0
position:016 ***** 0
position:015 ***** 1
position:014 ***** 1
position:013 ***** 0
position:012 ***** 0
position:011 ***** 1
position:010 ***** 0
position:009 ***** 1
position:008 ***** 0
position:007 ***** 1
position:006 ***** 0
position:005 ***** 1
position:004 ***** 1
position:003 ***** 1
position:002 ***** 1
position:001 ***** 1
position:000 ***** 1


here are some examples:









Good luck!

Boggy
Hello Mr. Petrovic,

I just want to let you know that I was able to create the longer sequence myself.

At the beginning, I asked for your help as I could not use the zip files the member robertopisa posted here.

I did not know the programming language Python before.

Opening these files reminded me how Robert Langdon tries to decipher the cryptex in The Da Vinci Code ...

Thanks anyway!

greetings
Matthew

Edit:
For those who are interested in a longer sequence.
I read here in another post from Boggy that coin flipping can be used if a longer sequence is needed than the one here given by him. I did that in the end.
Old 2nd November 2018
  #106
Quote:
Originally Posted by jhbrandt View Post
I thought I would share this for anyone who is brave enough to attempt.
The zip file is an Excel Spreadsheet.
This sequence gives a uniform/equal amount of 0s and 1s.
The pdf layout is in a grid of 61 by 83 positions without repeats.
Fun time.

Cheers,
John

-- I love math!
is this a panel with the sequence just applied from left to right and top to bottom or was it also spread using the chinese remainder theorem?
Old 20th April 2019
  #107
Here for the gear
 

Quote:
Originally Posted by jhbrandt View Post
I thought I would share this for anyone who is brave enough to attempt.
The zip file is an Excel Spreadsheet.
This sequence gives a uniform/equal amount of 0s and 1s.
The pdf layout is in a grid of 61 by 83 positions without repeats.
Fun time.

Cheers,
John

-- I love math!
John,

This is great you have provided this. I might give it a go. Let me explain how I am thinking in terms of design (polycyndrical perforated add on to a close to standard size of broadband absorber). I figure a good small room strategy is to make about 50% of a bunch of broadbad absobers with panels like this in front, so thay can be turned around sich as for listening, and some panels turned facing out for speech, more for music. The polycyndrical does make a 4" absorber thicker still, but then it will stand freely, which is another design preference if you want to reposition them.

This seems to ultimately take me to drawing a new grid, same numerical order, onto a top 1/8 ply sheet, the size I want, with 8 more sheets below it, then drill through the lot to get 8 panels - worth the trouble.

There is another post Adding a binary amplitude diffuser template onto an absorption panel where these are bent in front of a broadband absorber, I like it and thought this flooring trim would be good to secure it as long as there is an added bit of wood to fix them sucurely to the braodband absorber frame. door bars Laminate Flooring Trim 8mm Brass Effect: Amazon.co.uk: Kitchen & Home

But trying to figure out the size? That pdf template says it's A1 which is 841mm x 594mm. But at 100% ruler the spaces from hole centre to hole centre are 7.5mm. Then shouldn't it be printed on a 200% bigger sheet to get it to come out with 15mm spaces from hole to hole? I.e. when I measure what the template should be [Math: 61holes x 15mm= 915mm, 83holes x 15mm=1245mm] so its a usable grid of 915mm x 1245mm, but that size is bigger than the A1 size. Would I tell the printer to print it at 200% size or what?

It get's tricky, to work out sizing if I want to bend it in an arc. I also checked your link on diffussion panels (Thanks for that too), and I want to fit it on a standard broadband absorber that has an insulation width of 600mm and height 1200mm. So, good, you included the height of a recommended arc over a 600mm width panel as 93.5mm height from face. Using Calculator for Radius of an Arc I calculated, I hope correctly, the face-length of that arc as 638mm, height preference would be about 1200 to suit the size of the insulation panels.

So, then my preferance is to cut 1/8 ply sheets at 638mm x 1200mm (oh, I better make the absorbers so total height is 1200, trimming the insualtion a bit). I'll loose a bit, but I can get 3 peices from a 2400 x 1200 sheet. 3 sheets, to get 9 panels. Now I look back at the size of your grid, if 15mm between hole centres - 915mm x 1245mm. No your grid is a little bit too big for how I want to design it. Hopefull, my math is righ so far.

So, then I figure I am at the point where I want to use the binary sequence and reform it to a grid a little narrower than 638 to allow for a border, x say, 1180mm (20mm less at top and bottom to allow for a border. I figure I could do this by counting out the numerical sequence straight onto a drawn grid on the top sheet of ply for the drilling, rather than bother with a paper template.

Does all this make sense so far?
Old 26th August 2019
  #108
Lives for gear
 
bannerj's Avatar
 

[QUOTE=boggy....[/QUOTE]

Dusting off this thread as I prepare to build out my studio.

With all the fuss of size of hole and pattern, am I right to understand a few basic things here:

1. the random sequence of holes ensures that no single, repeated null will be created in reflections? The point is to scatter soundwaves in random directions.

2. the bigger the hole the more bass trapping/absorption vis a vis diffusion is occurring?


I know some of you high-end studio designers on here can get very technical and specific about the research behind all this. I'm asking as a mid-level studio operator. I'm about to put finish my first dedicated recording spot in an outbuilding.

Behind the two above questions is wanting to know what this piece flown in the studio below is accomplishing (what looks to be birch plywood with 3-4" holes under some sort of absorbing material).

Found this pic on Boggy's portfolio. Looks rad.

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