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Old 19th December 2003, 08:34 PM   #1
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Default DIY RPG "skyline" diffuser panel

I've been doing a lot of research lately on diffuser panels as acoustical treatment for the new basement listening room i've almost completed.

I'm really impressed with theRPG Skyline diffuser panels , but $150 for 1 2'x2' panel made of foam is a little out of my price range. I would like 5-6 of them.

Using the patent # found on the above link i researched on the US gov's patent site and i got the exact dimensions and placement of every one of those little peaks ( all 156 of them each one varying from 1mm-155mm)...and i plan on building an exact replica out of wood. I realize that acoustically it's not same thing then, losing some of the LF dampening that the styrofoam naturally provides, ...but i like the aesthetics of a stained wood panel WAY more than a styrofoam one anyways.

I realize that cutting 156 pieces of wood so they vary by 1mm is a pretty tedious project...so i'm debating the sonic impact if i were to round off the lengths of the pieces of wood to the nearest....say...5mm. That way i'd only have to cut around 31 different lengths of wood, and decrease my risk of losing a finger on the saw.

Anyways, I will build one of these panels shortly, and post my ingredients and progress shots as I go.

When i'm done with this, i'm going to build a similar DIY knock-off out of the RPG BadPanel , which i imagine will be much easier a project in comparison.

What are your thoughts?

-Maz
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Old 19th December 2003, 08:51 PM   #2
tiroth is offline tiroth  United States
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I would guess that the impact of rounding is virtually nil.
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Old 19th December 2003, 08:54 PM   #3
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well, if you look at all the math that went into that 17 page patent application...the amount of Prime number theory and whatnot.... you'd be under the impression that it would make a HUGE difference

But, i would imagine the sonics will be changed more by utilizing wood as my medium moreso than being off on the distances by a few mm.

-maz
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Old 19th December 2003, 09:06 PM   #4
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Ive met the RPG guys before and used some of thier products. Dr.D is a bright guy and there is truly science behind the products.

I know that there is at least one company making a knock off QRD diffuser. I don’t know if the RPG guys know that.

Most of the products they design start off as wood models. The investigations into foams and alternative materials come from the need to make lighter and affordable products. The skyline is designed to drop into a suspended ceiling frame.

Depending on what your looking for, I don’t think you’ll be too disappointed by following the concept of his design as apposed to the exact dimensions. I know others have done it without acoustic peril.

As far as the costs go, I guess it depends on perspective. If you think $120 for a well engineered JSG...

I know Ilbruk makes some nice cieling tiles, and for a product with a lot less scince in them (my opinion) they dont cost that much less. Set designers seem to like them for Sci-Fi sets too
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Old 19th December 2003, 09:20 PM   #5
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I have a friend who designed this room. He's a big fan and user ot the RPG product line:
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Old 19th December 2003, 09:46 PM   #6
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Thanks for the info.

I'm actually going to be coating the wall behind the listener with the panels...i realize they're designed to be either wall mounted or dropped into a suspended ceiling, and that has much to do with the choice of foam as the material. In my particular application, weight isn't any big deal.

If the listening room i'm building is a rectangle with the speakers and listener positioned at each of the far ends, then i'm planning on mounting an array of Skyline-style tiles behind the listener, and a length of Bad Panel's along the sides.

-Maz
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Old 27th May 2007, 03:49 AM   #7
dvisves is offline dvisves  United States
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Default DIY 2 Dimensional Diffuser

I have worked out the method for calculating the well depths for a Dimensional diffuser with Prime root 157.

1) Why use 157 : 157-1=156.156=13X12.13 is a Prime number.Also we want our diffuser to be square .Hence the rows and columns must be almost same.

2) Determine the prime root of 157.2 and 3 are not prime roots of 157 because (2 or3) raised to the power 1 to 156 modulo 157 show repeating values between 1-157.Hence 2 and 3 cannot be used.
Checking with 5 shows that it is a prime root of 157.
3)using the chinese remainder theorem make a matrix of 12X13 with congruence in the cells such that the number mod 12=row number and number mod 13=column.The matrix is as below


1 145 133 121 109 97 85 73 61 49 37 25 13
14 2 146 134 122 110 98 86 74 62 50 38 26
27 15 3 147 135 123 111 99 87 75 63 51 39
40 28 16 4 148 136 124 112 100 88 76 64 52
53 41 29 17 5 149 137 125 113 101 89 77 65
66 54 42 30 18 6 150 138 126 114 102 90 78
79 67 55 43 31 19 7 151 139 127 115 103 91
92 80 68 56 44 32 20 8 152 140 128 116 104
105 93 81 69 57 45 33 21 9 153 141 129 117
118 106 94 82 70 58 46 34 22 10 154 142 130
131 119 107 95 83 71 59 47 35 23 11 155 143
144 132 120 108 96 84 72 60 48 36 24 12 156
Now the numbers in the matrix are place holders for 5 raised to the power n mod 157.

Transposing the values we get the diffuser configuration as below.


5 151 70 73 38 80 61 21 69 137 24 34 22
110 25 127 36 51 33 86 148 105 31 57 120 13

65 79 125 7 23 98 8 116 112 54 155 128 129
17 11 81 154 35 115 19 40 109 89 113 147 12

60 85 55 91 142 18 104 95 43 74 131 94 107
64 143 111 118 141 82 90 49 4 58 56 27 156
152 6 87 84 119 77 96 136 88 20 133 123 135
47 132 30 121 106 124 71 9 52 126 100 37 144

92 78 32 150 134 59 149 41 45 103 2 29 28
140 146 76 3 122 42 138 117 48 68 44 10 145
97 72 102 66 15 139 53 62 11 83 26 63 50
93 14 46 39 16 75 67 108 153 99 101 130 1

the numbers in the matrix represent the proportional height of the diffuser wells.

I have also been able to work out the diffuser configuration with prime number 601.

Hope this is of use to some DIYer out there
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Old 27th May 2007, 02:56 PM   #8
marekst is offline marekst  Poland
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I have some experience in the matter; I had to grow back the tip of my thumb! No doctor saw it either, I spend all my money on audio so I can’t afford doctors.
The panel you have chosen is not the best for DIY. Making 31 cuts instead of 156 will definitely change the principle the panel is build on. First you have to determine what you want - like frequency range and how much of diffusion you need. One skyline panel placed on back wall will have very limited effect, even in its designed frequency range. Many panels may take more then one finger; effectiveness will increase but frequency range only a little. The omniffusor based on prime7 is easy to make out of wood with only 6 different lengths to cut, but again, it is not necessarily what you need.
http://gallery.AudioAsylum.com/cgi/g...1150&f=SP1.jpg
I am not en expert but I do have diffusive back wall and I like the spacious sound of my medium size room. Anything effective at low frequencies has to be biiiiiiiiiiiig! You may be better of with absorption on the back wall. The problem is a complex one, opinions very, the best way is to thoroughly study The Master Handbook of Acoustics by F.A.Everest before you make any decisions. The 3RD Edition has a chapter on RPG products.
In my opinion room acoustics are responsible for 30% of the sound and I would not hesitate to spend 1/3 of my audio budget on it.
Have fun,
Marek
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Old 6th March 2009, 12:58 AM   #9
Rewind is offline Rewind  Sweden
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Default RGP guide: Now in multicolor!

The first statement that the highest point is 15.5 cm according to the patent is probably a misconception. But of course you will only be 0,6 cm off the original if you just add the unit [mm] to the "Table 5" in the US patent. In reality the highest column is 16.1925 cm, according to RPG´s own PDF. If you just add [mm] to Table 5 you will be off maxmimum 6,1925 mm. That is about how wide your saw is, i.e. it is neglectable.

In my own enterpretetation of these numbers I have chosen 15 different lengths which is more than accurate. See my picture!





This is directly from the Skyline patent:

"(1) The primitive root is raised to the power of the number of the particular well chosen. For example, for well 3, one takes the primitive root 5 and raises it to the third power. The resulting number 125 is divided by the chosen prime number 157 which leaves a total of 0.7961783. When this last-mentioned number is multiplied times the prime number 157, the residue is 125.

TABLE 5 __________________________________________________ ________________________ 5 151 70 73 38 80 61 21 69 137 24 34 22 110 25 127 36 51 33 86 148 105 31 57 120 13 65 79 125 7 23 98 8 116 112 54 155 128 129 17 11 81 154 35 115 19 40 109 89 113 147 12 60 85 55 91 142 18 104 95 43 74 131 94 107 64 143 111 118 141 82 90 49 4 58 56 27 156 152 6 87 84 119 77 96 136 88 20 133 123 135 47 132 30 121 106 124 71 9 52 126 100 37 144 92 78 32 150 134 59 149 41 45 103 2 29 28 140 146 76 3 122 42 138 117 48 68 44 10 145 97 72 102 66 15 139 53 62 114 83 26 63 50 93 14 46 39 16 75 67 108 153 99 101 130 1 "
__________________________________________________ ________________________

References:

Measurements in RGP's own PDF: http://www.rpginc.com/products/skyline/skyline.pdf
index.htm

Building hints for wood fanatics: http://www.canuckaudiomart.com/forum...pic.php?t=8456

Buildning hints for the plastic fantastic: http://www.bobgolds.com/DifuserKgveteran/home.htm

US Patent: http://patft.uspto.gov/netacgi/nph-P...401,921:angel:
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