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RPG Bad Panel -- Detailed Plans
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#61
4th February 2011
Old 4th February 2011
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Quote:
Originally Posted by jacktiki411 View Post
FWIW I have several of these panels. They definitely have the 1/8" grid. You can feel it through the cloth.

It's funny. I got these by accident. They were listed as absorbers on ebay. I bought them and they were BAD panels. I'm just starting to treat my room so I'm still trying to figure out how to use them. Right now I have two on the ceiling and the rest temporarily sitting on TV tables in the front corners! They did tighten up the room significantly but I haven't done any measurements and I know that they are not being used as intended yet. I have to build some proper bass traps, first and then figure how to use them. Sorry for the blather - I just wanted to be clear that while I have them I can't give an honest opinion on how they work.

Neil
Neil,

So, you say the holes are 1/8"? How big is the space between adjacent holes? I mean the smallest space between holes? Is it also 1/8", or something larger/smaller.
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#62
4th February 2011
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I apologize. I meant that it is that 1/8" hardboard not a film. It's really hard to say the space between the adjacent holes as the distances are different and not easy to see with the fabric over top.

Neil
#63
5th August 2011
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I have made several of the BAD-panels for my listening room. Both the curved version and the newest ternary version which also offers a "variable" -1 reflection function, besides the 1 and 0 from the template. I think they work great. Quite straight forward work, plus easy and cheap to DIY, all the holes are a bore to drill though.

To make Angus grid of 31x33 rows of holes suit a quadratic template, the hole pattern should be 19,19x18,03 mm for a template of 600x600 mm. Making it quadtratic 600x600 mm is only to make it sutable versus existing building and sheet standard dimensions (in the US module 24"x24").

Some pictures how they turned out: Salong Svarta Katten - Component forum - Page 8 and Salong Svarta Katten - Component forum - Page 11 The larger Ternary BADs along the long walls, each consist of 8 templates with varying positive and negative hole pattern, to decrease possible loobing. Size/pcs is 2,44x1,22 m (96" x 48") with some 4000+ 12 mm holes in each.

To make the improved ternary version is easy-peasy with a cone made of i.e. 3 mm thick rubber Ø 273 mm. I think you get the picture how, just by looking a bit further up in the thread (in case you got an F in Swedish ;-) )

Edit: I wrote an excel spread sheet to "tailor make" any sheet size with hole pattern to suit wall dimension in the room. Drop a line, in case you´d like to have it.
#64
5th August 2011
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wicked - thanks!
#65
5th August 2011
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Quote:
Originally Posted by Adhoc View Post
I have made several of the BAD-panels for my listening room.
OK, those are awesome. Thanks for posting!

Quote:
all the holes are a bore to drill though.
As a non-native English speaker I bet you didn't mean it, but to native speakers that is actually quite a good joke.

Glenn has suggested to use NC equipment to make diffusers, but I don't think that they are as desirable there as they would be for these. For ones like yours, though, the problem might be that it would be difficult to find a shop with a machine with a large enough table - and that it probably gets exponentially more expensive for time the larger the machine (since then they also usually get heavier duty and much more expensive).

I bet a lot of people are going to want that Excel sheet, so I'd suggest posting it as an attachment.
#66
5th August 2011
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A CNC machine is only necessary if you intend to manufacture large numbers of templates for profit. tutt says RPG and sentence you to . For several panels and for personal use, you could draw the grid on a piece of good plywood or bendable hard board (masonite (?) if you wish to make a curved BAD). Mark out the hole pattern and stack a number of undrilled templates on each other. Drill a few holes, insert screws + nuts and tighten the package. Make sure you always have undrilled holes at “good places” and move around the screws + nuts until the drilling is finished. You can count with lots of debris and about an afternoons work of easy but tedious drilling for a 500+ holes template.

I made the larger 2x4 panels from 2440x1220x4 mm pine plywood with an abrasive waterjet at work. It takes a lot of computing power for the vectors for 4000+ holes! Depending on computer power it may be better to make panels 1x1 with 500+ holes. Companies manufacturing articles from sheet goods, like interior doors, loudspeaker boxes, etc have router bits in their CNCs. These machines are a lot faster than a waterjet, probably around 15 minutes machining time per template.

The “hole ó bore” was actually an intended pun and you got the ambiguity .
#67
5th August 2011
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Quote:
Originally Posted by Adhoc View Post
I have made several of the BAD-panels for my listening room...
That's a pretty amazing room you have there ! Thanks for sharing.
#68
5th August 2011
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Quote:
Originally Posted by aackthpt View Post
I bet a lot of people are going to want that Excel sheet, so I'd suggest posting it as an attachment.

It appears to be the same sequence as the original posted in this thread. The negative of the sequence is inverted and placed below. Next to that vertical pair is the whole thing spun 180. Lather rinse repeat.



It looks absolutely stunning by the way. I'm elbow deep in a number of these panels myself. Seeing them in your room gives me hope.
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#69
5th August 2011
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Quote:
Originally Posted by johndykstra View Post
It appears to be the same sequence as the original posted in this thread. The negative of the sequence is inverted and placed below. Next to that vertical pair is the whole thing spun 180. Lather rinse repeat.



It looks absolutely stunning by the way. I'm elbow deep in a number of these panels myself. Seeing them in your room gives me hope.
Thanks for the cred!

The former junk room turned out better than what I had hoped for. Size of the hard shell is 786x420x220 cm with 20 cm (8") concrete walls, ceiling and floor. A night mare without treatment and a heaven for 80-90 Hz resonances. Hidden in the room there is roughly 1,5 m³ (53 ft³) of 705 glass fibre and about 10 m² (108 ft²) of high density rubber membrane absorbers (soft layer absorbent, as Floyd calls it in his recent book), to tame the bass. There are also 6 subs used for the same purpose. Bass response feels very smooth along a 2 m-width and roughly 0,6 m depth at center in the room.

The hole pattern is like the patent. The grid size has been slighly changed to suit European standard module of 600 (595) mm instead of American 24". Optimal sequence for positive / negative templates for minimal loobing with 2x4 templates integrated into one, could not be followed but I did what could be done.

I made a quick translation to English of the spread sheet, in case anybody can have use for it.

Edit: saw a few words I forgot to translate ie "33-längden" = 33 square row, "ytterarea, m²" = total sheet size, m²
Attached Files
File Type: xls BAD-panel versions.xls (109.0 KB, 1106 views)
#70
23rd August 2011
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I had a band member that uses a CNC machine at work make me 12 4x4' bad panels and love the result they give. I have a very heavily dampened control room and they seem to have made the room cleaner and clearer without changing the sound of the room. Definitely helped define the 2 to 5k area..
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#71
25th August 2011
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Quote:
they seem to have made the room cleaner and clearer without changing the sound of the room
#72
26th September 2011
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Quote:
Originally Posted by Adhoc View Post
Thanks for the cred!

The former junk room turned out better than what I had hoped for. Size of the hard shell is 786x420x220 cm with 20 cm (8") concrete walls, ceiling and floor. A night mare without treatment and a heaven for 80-90 Hz resonances. Hidden in the room there is roughly 1,5 m³ (53 ft³) of 705 glass fibre and about 10 m² (108 ft²) of high density rubber membrane absorbers (soft layer absorbent, as Floyd calls it in his recent book), to tame the bass. There are also 6 subs used for the same purpose. Bass response feels very smooth along a 2 m-width and roughly 0,6 m depth at center in the room.

The hole pattern is like the patent. The grid size has been slighly changed to suit European standard module of 600 (595) mm instead of American 24". Optimal sequence for positive / negative templates for minimal loobing with 2x4 templates integrated into one, could not be followed but I did what could be done.

I made a quick translation to English of the spread sheet, in case anybody can have use for it.

Edit: saw a few words I forgot to translate ie "33-längden" = 33 square row, "ytterarea, m²" = total sheet size, m²

If your work sounds as good as it looks,your on a winner....
#73
25th October 2012
Old 25th October 2012
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If you make the fiberglass insulation 4" thick, wouldn't this make it an effective basstrap aswell?
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#74
25th October 2012
Old 25th October 2012
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Depends on how one defines "effective" and "basstrap".

The link shows what RPG reports on absorbtion for different thicknesses. If one digs down to their other technical specifications, they use high density glass fiber behind the panel, in the region of Owen Cornings 705.

http://www.rpginc.com/ProductDocs/BA...cal%20Data.pdf
BAD EXPO Product Detail

For some fairly new built ones I used a smaller hole diameter (10 mm) and 300 mm depth with low weight / low gas flow resistivity plus an air tight box behind the panel. Goal: To improve on the absorbtion for lower frequencies (should be "good" down to about 63 Hz) as well as rapidly decreasing absorbtion above 500 Hz = improved reflection / diffusion for a more "live" room.
#75
26th October 2012
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Quote:
Originally Posted by Adhoc View Post
For some fairly new built ones I used a smaller hole diameter (10 mm) and ...
By any chance did you figure out the perforation percentage for those panels?
And do you know if the diffusion coefficient changes by changing the hole diameter?

Thanks,
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#76
26th October 2012
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Quote:
Originally Posted by John White View Post
By any chance did you figure out the perforation percentage for those panels?
And do you know if the diffusion coefficient changes by changing the hole diameter?

Thanks,
The binary amplitude grating assumes a 50% perforation.
#77
26th October 2012
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I see. So please don't feel the need to answer for him, but the smaller hole diameter would upset that balance. Yes? Then it must be assumed it diminishes the effect of the diffusion. As it is, I can't see them being much use except in very small spaces.
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26th October 2012
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Quote:
Originally Posted by OpusOfTrolls View Post
The binary amplitude grating assumes a 50% perforation.
Not necessarily. The idea behind RPGs BAD panel originated from Angus and that idea was probably for a 50-50 relationship.

But ... depending how you may wish to "tailor make" your panels performance, you can see it as: Here is the centre for a perforated area + here is the centre for an unperforated area. => You decide how big you want the holes to be which of course determines the relationship between perforated and unperforated area => a helmholtz device with some diffusing properties because of the hole pattern, diffusing properties can be further improved by curving the frontpanel.

If I remember correctly, RPGs original with 511 pcs 1/2" holes has about 22% perforation, with 10 mm holes instead the perforation decreases to about 9%. (It is an easy area calculation but I don´t have a calculator ready now.)

RPG chose to have a smaller perforated percentage compared to the "reference panel" in their technical report. Smaller holes gave higher low frequency absorbtion and a higher reflection/diffusion of higher frquencies. The results are clearly written out in RPGs on technical report.
#79
26th October 2012
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Quote:
Originally Posted by Adhoc View Post
Not necessarily. The idea behind RPGs BAD panel originated from Angus and that idea was probably for a 50-50 relationship.

But ... depending how you may wish to "tailor make" your panels performance, you can see it as: Here is the centre for a perforated area + here is the centre for an unperforated area. => You decide how big you want the holes to be which of course determines the relationship between perforated and unperforated area => a helmholtz device with some diffusing properties because of the hole pattern, diffusing properties can be further improved by curving the frontpanel.

If I remember correctly, RPGs original with 511 pcs 1/2" holes has about 22% perforation, with 10 mm holes instead the perforation decreases to about 9%. (It is an easy area calculation but I don´t have a calculator ready now.)

RPG chose to have a smaller perforated percentage compared to the "reference panel" in their technical report. Smaller holes gave higher low frequency absorbtion and a higher reflection/diffusion of higher frquencies. The results are clearly written out in RPGs on technical report.
I didn't know that, thanks!
#80
6th November 2012
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Thinking of making a couple of these (2'x4') in a Poly config.

I have the perfect thing for the easiest grid:
ceiling grid for florescent lighting


Fits perfect over a 2'x4' plywood panel. (the plastic measures 23.75" x 47.75", and there's 37 squares across the width) If i discard the first two squares either side, my sequence should fit perfect. Should work out great! (though i dread the mindless drilling...)
#81
7th November 2012
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RPG Bad Panel -- Detailed Plans-bad_temp.jpg

I dread drilling the holes. The squares work out to fit a 9/16" drillbit perfectly. The plastic light-cover should work out great for a template and drill guide.

Any tips on bending the poly once the holes are drilled? I've made smaller 18"x18" poly-diffusors using a steam-mop to loosen the wood, but nothing this big (2ft x 4ft)... and with the smaller ones i made a bonding jig so it held the shape as it dried.
I don't think i'll be able to do so with the larger one, though i will be using a semi-circle skeleton every foot or so to bond it to. i'm just wondering if there's a better way to steam the wood and hold the shape while the wood dries..
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7th November 2012
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Aww,

Did you decide on the hole size in regards to absorption?

Two notes:
Light plastic maybe a weak guide so be gentle. Are you enlarging the pattern printout to place under the grill or just counting left to right/ up and down?

Bending the panel seems redundant. By nature, the diffusion within the corresponding frequency range should be sufficient to provide whatever scattering one would get in bending the panel. At least that's what it seems to me.

Another note- If you make several panels you may be able to drill them all at once with a sharp bit. Hence, saving time.
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7th November 2012
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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.
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7th November 2012
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Thanks, Aww- sounds like a good project.

Quote:
Originally Posted by AwwDeOhh View Post
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.
When you write, "With the pattern I'm using", what do you mean? Does this suggest the scale of the hole pattern can be changed? As in the center to center measurement can be scaled. Again, I have to assume this would alter the diffusion coefficient even more so than the hole size.

Still not sure if anyone can relate just how this affects the usage of the pattern.
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7th November 2012
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To save me from counting the holes, does anyone know the number of perforations (holes) within a complete cycle/ one unit of the BAD?

Assuming each "Unit" is 2x2' (Please correct me if I'm wrong) I'll calculate your perforation percentage at 1/2" and 9/16" as well as the target absorption frequency using your 6" depth.
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7th November 2012
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I'm trying the pattern posted in post #40 by mobius (though i might just calculate my own, i haven't decided).

In post #40 the pattern is 33 'squares' wide (and 31 tall). The plastic grid i have is 37 squares wide (the plastic itself is aprox 1/16" thick so that will be my spacing) Like i said, i could make a unique pattern that uses all the width (ie goes all the way to every edge of the plywood), but it actually works out good discarding the first two holes (of the plastic) either side for mounting purposes... if that makes sense.

{EDIT} i counted 508 'holes' on the first grid out of 1023 possible slightly weighting the reflective over absorptive (which is why i'm using slightly larger holes)
#87
7th November 2012
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To help visualize:
Name:  bad2.png
Views: 1447
Size:  150.3 KB

The brown is the actual wood's edge
#88
8th November 2012
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Upon closer inspection to that program, they have 16.xx% for the open area. I'll look at later. Still, 16% seems quite high for reflectivity. I still wonder how a lower % would affect the quality of the panel. I also noticed they had a high frequency cut off of the diffusion though I couldn't get the numbers to jive myself.
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8th November 2012
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Quote:
Originally Posted by AwwDeOhh View Post
Any tips on bending the poly once the holes are drilled? I've made smaller 18"x18" poly-diffusors using a steam-mop to loosen the wood, but nothing this big (2ft x 4ft)... and with the smaller ones i made a bonding jig so it held the shape as it dried.
If you are only making a few, taking the time to build a jig probably isn't worth the effort. I assume you've seen the how-tos in various places about building polys? The Everest book has details, there are threads here, etc. I looked back but didn't see specifics about the wood you plan to use. Plywood, right? What thickness?

I knew a studio owner near Chicago that long ago built a bunch of large polys. He used 3/4 plywood as the curved frame member to support the 1/4" plywood he used as the curved surface. So imagine cutting a "D" shaped piece out of 3/4" plywood. He made about 20 polys that were in 8' sections and had the D shaped struts every 4', so that meant he had many pieces of 3/4" plywood that were the left-over from cutting out the D. So he took all of those left-overs and made a jig. He'd cut the 1/4" plywood face, lay it on the jig, then added sand bags to gravity-force the 1/4" down into the jig. Then he'd glue and nail (from below) the 1/4" plywood to the D pieces. The D's were then connected to each other with thin pieces of hardwood along the edge of the 1/4" plywood. Sorry if that is confusing, no time to try to draw a sketch right now.
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8th November 2012
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that actually makes alot of sense. thanks! Use the 'relief' from cutting the 'D' as the negative form.

i'm going to use 1/8" ply to (hopefully) make the bending easier.

In the Everest book they just show a guy wrangling the panel around the 'D' struts. I plan on using steam as that should help prevent cracking.

the way i did it before was only good for smaller pieces, as the steam mop couldn't saturate a large area. I'm wondering if i should use a sort of plastic bag cover to help contain the steam over a larger area. (it doesn't help that i'm doing this in my garage, and it's getting friggin cold outside)
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