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RPG Bad Panel -- Detailed Plans
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#91
8th November 2012
Old 8th November 2012
  #91
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The bag should work fine. I know a builder that makes hardwood chairs with bent and twisted boards. He uses a bag for his steam treatment.

Please put up some pictures as you build!
#92
9th November 2012
Old 9th November 2012
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Quote:
Originally Posted by AwwDeOhh View Post
Was going to use .5", but am going with 9/16 (only slightly larger) for a bit more absorption in the equation. i'm retro-fitting some 6" deep panels on the back wall (there's already QRD and some polys inbetween as well as QRD's on the back sides and a prd skyline on the ceiling) to help even out the rooms' decay a bit more (there's aLOT of absorpiton in my small room). I've got the low end pretty much under control (as much as it can be in this room) but the decay falls off more than i'd like in the mid-to-high end. If i don't like how they turn out (for the room), i can always put them on my Gobo for another tracking option.

Yes the acrylic plastic grid won't put up a fight against a drillbit, but it saves me from drawing out the grid, and if i can keep the drill from touching any side of the square, the hole should be darn close to vertical (there is only the very slightest bit of wiggle room w/ 9/16 bit)

With the pattern i'm using there will be 1.5" of "unused" space around the edges, which i figure should be plenty enough for mounting hardware or any trim i might add.
If you read through all RPGs papers on BADs carefully, you will find a
diagram showing panels with 1/2" and 5/8" holes.

Results from the diagram show that 5/8" holes versus 1/2" will give:
Less reflection/diffusion for higher frequencies (usually seen as worse performance)
Less absorbtion for lower frequencies (usually seen as worse performance).

Personally I would not use that plastic grid, 37 squares wide, but mark out all the holes with a good ruler / square directly on one piece of plywood, clamp together a number of plywood sheets and drill them all at the same time.

4 mm or 1/8" plywood is quite bendable even with out steaming, with little risk of cracking if you use 1/2" holes versus a 20 mm (3/4") inch grid. You will need D-shaped sides and also straight pieces of wood between these D-shapes, to nail down the plywood. It will bend up "a bit" in the middle otherwise. (This is from my practical DIY experience on BAD-copying.)
#93
9th November 2012
Old 9th November 2012
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Thanks for refreshing my brain on the 1/2 vs 5/8" data, Adhoc. I'd waded through a bunch of their tech pages and had forgotten that tidbit.

I can't remember if you have mentioned how much of a bend you have in your panels?

Even 3/4" plywood can be bent quite a bit if you cut 3/8" deep reliefs in the back. I've built highly sculptured climbing walls this way that retained strength and stiffness very well. I'd fix one edge and as the bends were being secured to the frame, fill the reliefs from behind with gorilla glue.

I think I've talked myself into using BAD panels in my about-to-start mix room build. I picked up the hardwood flooring last week and am about to rip out the carpet. Yippee!
#94
9th November 2012
Old 9th November 2012
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Depths of the curved shapes varies, they where chosen depending on where in the room the panels were placed, 1210 x 70 mm, 1000 x 102 mm, 895 x 185 mm etc. The curve in the pictures below, from my first experiment with the BADs in my previous flat (2007), is 1000x102 mm. Total dim 2000 x 250 mm deep, with insulation inside it works pretty well as a low frequency absorber too.

An easy way to make a smooth curve is to mark the unbent width of the panel as well as the center between the marks on a slim strip of easily bent Masonite (the Masonite should be about 12 inches or so longer than the width of the panel). Hammer 2 nails onto the board to be D-shaped and mark out the center between them. Now, push up the Masonite between the nails, center mark to center mark until you get your wanted depth and mark out the curve with a pencil.



#95
9th November 2012
Old 9th November 2012
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Thanks Adhoc.
Ends up i need to use 1/2" holes anyhow...
After drilling 5 rows of holes with the 9/16" bit, i noticed that i'm getting some tear-out between some of the holes. The plywood just doesn't like that tight of spacing. (but the MDF scrap i was using underneath has beautiful holes! )
I've decided to salvage some of the ply anyhow by starting on the other end of the board and going for two 2'x2' panels w/.5" holes. Doing 1/2" holes gives me about 3/16" spacing between holes (with the help of a hole punch/marker to keep the bit from wandering)

If i do as you say and draw out a grid, how big should the squares be? should i just divide it up evenly from end-to-end (to get 33 squares wide)? Should i do another sequence that is 37 squares?

I'll have to get some more material to give the 2x4' panel(s) another go. Luckily i haven't invested too much time before noticing the damage.
#96
9th November 2012
Old 9th November 2012
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For 2'x2' panels = square and not rectangular, the grid size should be slighly less than 3/4" x 3/4" if you want a trim around the edges. Check up the spread sheet in post 69 for exact measurent on the different width and height for a square panel. If it is OK with a rectangular panel, you go with equal width an height.

If you buy a forstner drill bit for the holes, you will get less tear out on the backside (compared to a normal drill bit with 118 degree angle). High speed together with low force gives best result.
#97
10th November 2012
Old 10th November 2012
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Quote:
Originally Posted by Adhoc View Post
For 2'x2' panels = square and not rectangular, the grid size should be slighly less than 3/4" x 3/4" if you want a trim around the edges. Check up the spread sheet in post 69 for exact measurent on the different width and height for a square panel. If it is OK with a rectangular panel, you go with equal width an height.
The plastic 'grid' is exactly 5/8" squares (with 1/16" 'lines'). Since i'm already halfway through drilling .5 inch holes, i'm just going to finish these and see how they turn out. Next build i'll grab better quality material and draw a proper grid. I'm just anxious to see what kind of effect these have compared to other diffusors. Was worth a try anyhow...

Quote:
Originally Posted by Adhoc View Post
If you buy a forstner drill bit for the holes, you will get less tear out on the backside (compared to a normal drill bit with 118 degree angle). High speed together with low force gives best result.
Yeah.. i'm used to working with metal (used to work in a metal fab shop), so most of my equipment is geared towards that. Thanks for the tip.
Too bad i can't fit this thing under my drill-press... that would be perfect!
#98
11th November 2012
Old 11th November 2012
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While a press would be faster, if you have a good drill with bubble level, it would be just as simple.
#99
24th November 2012
Old 24th November 2012
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Here's the prediction for my first shorcut attempt
RPG Bad Panel -- Detailed Plans-bad_tst_grph_01.jpg

Pics to follow
#100
21st December 2012
Old 21st December 2012
  #100
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hi!
just curious as I'm sure a bunch of you on here know way more about this than me: would it work to basically "grow," or scale up this design x4 so the grid is 2" squares instead of .5" ? doing that would lower the range of frequencies that the diffuser works at right?

backing would remain the same, a 4" piece of OC705 or similar

#101
21st December 2012
Old 21st December 2012
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If you have Excel (windows Office), or even OpenOffice you can use this:

Porous Absorber Calculator V1.59

At the bottom of the Excel sheet, there's a tab for predictions other than porous absorbers; you should find what you're looking for there.
#102
21st December 2012
Old 21st December 2012
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larger openings tend to affect the HF more than the LF. however the BAD panels are "amplitude grating" which means the numeric periodicity of the panel has a specific relationship to the underlying absorption which defines it operating characteristics... so simply trying to scale it differently than defined by RPG could lead to unexpected results

on making these types of panels - there are a lot more CNC machines around in local shops so you might find it a huge time saver (and reasonable cost) to provide the blanks and a simple CAD file with the layout and let them do the precise cutting of the openings... http://en.wikipedia.org/wiki/Milling_machine
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#103
21st December 2012
Old 21st December 2012
  #103
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These Keypacs from auralex Auralex Acoustics - KeyPacs have bigger holes, I can't find any info about them. But they look easy to build.

Best regards,

Peter
#104
21st January 2013
Old 21st January 2013
  #104
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After reading this post, we recently decided to build some BAD panels for a small 5.1 control room and they work really well, we used 4 mm MDF for the frontal face and 4" airspace filled with rigid black mineral fiber.

RPG Bad Panel -- Detailed Plans-dsc05666.jpg

RPG Bad Panel -- Detailed Plans-bad.jpg

RPG Bad Panel -- Detailed Plans-bad1.jpg
#105
21st July 2013
Old 21st July 2013
  #105
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Hi fellas, here are a few template attachments for the panels, one straight, one inverse. Take the files to a copy or print shop capable of construction blue printing, and make the hole sizes too what you see fit for your application.

the best part of these files, is the the center marks for each hole. Stack 15 pieces of HB 1/8 and drill them all at once

you're welcome

Edit; I noticed an anomaly! the third line up on the straight pattern is not book matched or mirrored from the middle, and missing a hole on the far left. I checked the illustration from the patent(attached), and it is the same as the template i made, i think, judging by the entirety of the pattern, the original is missing 1 hole, make your adjustment accordingly?, i don't think a single hole amiss in the pattern will kill your room either way
Attached Thumbnails
RPG Bad Panel -- Detailed Plans-bad-panel.png  
Attached Files
File Type: pdf bad.pdf (302.0 KB, 264 views) File Type: pdf bad inverse.pdf (297.2 KB, 175 views)
Quote
1
#106
21st July 2013
Old 21st July 2013
  #106
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Hi Tony,

Thanx for the drawings! What are the dimensions of the drawing.

best regards,

Peter
#107
21st July 2013
Old 21st July 2013
  #107
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Quote:
Originally Posted by petertjed View Post
Hi Tony,

Thanx for the drawings! What are the dimensions of the drawing.

best regards,

Peter
hey Peter,

what i did was expand everything from the original respectively. i ended up with various big sheets, starting around 24" sq to 36" sq, with the hole sizes ranging from .5", .75" and 1" give or take(cost about $6). So i guess the answer to your Q is, i don't know
#108
21st July 2013
Old 21st July 2013
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Quote:
Originally Posted by petertjed View Post
Hi Tony,

Thanx for the drawings! What are the dimensions of the drawing.

best regards,

Peter
You can fix your own dimensions / "drawings" of your panels with the excel spread sheet here:
RPG Bad Panel -- Detailed Plans
#109
21st July 2013
Old 21st July 2013
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judging by adhoc's post, the third line up on the far right, that dot should be eliminated, and don't forget the inverse. Sorry for the confusion.
#110
25th August 2013
Old 25th August 2013
  #110
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Can someone clarify if these grating designs will ultimately absorb more high end than return it?

I'm trying to interpret both the RPG and Kinetic's published specification data, but its seems as though the absorption coefficient exceeds or overlaps the scattering coefficients in both designs? Either that or crossover is way up around 10K+

Am I interpreting this correctly? I'm sure there is more high end reflecting than a typical broadband absorber, but ultimately it seems as though the high end is still getting more absorbed than diffused/scattered?
Attached Thumbnails
RPG Bad Panel -- Detailed Plans-kinetics-tad-acoustic.jpg   RPG Bad Panel -- Detailed Plans-badac2.gif   RPG Bad Panel -- Detailed Plans-bad_panel_dc2.gif  
#111
28th August 2013
Old 28th August 2013
  #111
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You are not.

They have a lower absorption coefficient than plain fiber above ~1k. This means they absorb less.

They have a higher scattering coefficient than a flat panel (reflector), so they work as quasi diffusion.

I had a small live room/practice room that was lined on the walls with staggered broadband absorbers. I face each of those with grating surfaces and the difference was amazing.

The room felt far less oppressive, and drum recordings are night and day better. More "snap", more "air".... like taking the blanket off your ears.
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#112
29th August 2013
Old 29th August 2013
  #112
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Great!
Glad my assumption was wrong
#113
11th September 2013
Old 11th September 2013
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Surprisingly, they are also effective as absorbers in the range 100-200Hz, maybe because they vibrate.

Here are the files with the AutoCAD coordinates in case you want to use a CNC machine.

https://mega.co.nz/#!No9yDSyR!VncMVF...GmvKzEyF7q1YgE

Please note that, although RPG BAD are patented, the binary hole pattern is free since it already appeared in Number Theory in Science and Communication: With Applications in Cryptography, Physics, Digital Information, Computing... by Manfred Schroeder (first edition is 1984).

I am using these, built using 2mm PVC on a wood frame:

Quote
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NLP
#114
11th September 2013
Old 11th September 2013
  #114
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... do you have "negative" pattern?
#115
11th September 2013
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I have Python scripts that can generate also the negative pattern but please note that I never saw mentioning negative patterns for these in Schroeder's writings (at least what I have seen so far). Are you sure that they are helpful?

Quote:
Originally Posted by NLP View Post
... do you have "negative" pattern?
Anyway, I just need to invert the data and run the scripts to have them.

rpg-bad-invertd.zip
NLP
#116
12th September 2013
Old 12th September 2013
  #116
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Thanks.
I have positiv and negativ when they published patent, but for other members.
... you can calculate your own "BAD" sequence...

In acoustics is not advisable to have in room same periodic continuously repeating elements (lobing), then you may use combination of positive and negative elements with Barker code sequence or similar... or just calculate/made many different elements

Example from BAD patent:
Patent Images
Look
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#117
12th September 2013
Old 12th September 2013
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+1 to NLP. You cannot keep strictly to the Barker code though, if you integrate 2 x 4 panels of 2' x 2' (60x60 cm) onto 1 large standard sized plywood sheet. I just inserted 2 negative ones among the other 6 positive ones. (The one in the picture is sawn off a bit, due to a door to the right)

#118
12th September 2013
Old 12th September 2013
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I see your point, I did not notice the difference as I am not using an array of BAD panels. It's good to know.

-R


Quote:
Originally Posted by NLP View Post
Thanks.
I have positiv and negativ when they published patent, but for other members.
... you can calculate your own "BAD" sequence...

In acoustics is not advisable to have in room same periodic continuously repeating elements (lobing), then you may use combination of positive and negative elements with Barker code sequence or similar... or just calculate/made many different elements

Example from BAD patent:
Patent Images
Look

Quote:
Originally Posted by Adhoc View Post
+1 to NLP. You cannot keep strictly to the Barker code though, if you integrate 2 x 4 panels of 2' x 2' (60x60 cm) onto 1 large standard sized plywood sheet. I just inserted 2 negative ones among the other 6 positive ones. (The one in the picture is sawn off a bit, due to a door to the right)

#119
17th September 2013
Old 17th September 2013
  #119
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Cloud for the ceiling?

What if we use six 60x60 BAD panels and rockwool plus a wood frame to build the following cloud?
  1. First, the wood frame: each square is empty internally (60cm x 60cm) and there are four hooks (in red) that will bind the wood frame to the ceiling at the proper height.

  2. Second, thick rockwool or similar: just stack it on the top the wood frame and link them in some way.
  3. Third, the six 60x60 (i.e. 2'x2') BAD panels: they are suspended using wires at the proper (and variable) distance below the wood frame. Each panel is suitably oriented so as to have a different frame-distance from the others and to deviate reflections (as in RFZ).

It seems to me that it is a reasonable project. Any comments or ideas please?

-R
#120
21st September 2013
Old 21st September 2013
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just like to say a big "Thank you =)" to robertopisa as I have been struggling to find software to convert the BAD-panel drawings to autocad format for some time, you saved me literally hours of work.
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