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Thermoformed
Quadratic Residue Diffusor
A
The Thermoformed Quadratic Residue Diffusor shall be the model Formedffusor™
as manufactured by RPG® Diffusor Systems, Inc., Upper Marlboro, MD 20774.
Tel: 301-249-0044, Fax: 301-249-3912.
B
The Thermoformed Quadratic Residue Diffusor shall be fabricated from fire retardant
acrylic PVC.
C
The Thermoformed Quadratic Residue Diffusor shall work on the one dimensional
reflection phase grating principle, using an array of wells of equal width separated
by thin dividers. The depths of the wells shall be based on the prime seven
quadratic residue theory sequence.
D
Sound diffusion in the horizontal plane shall be provided by wells in the vertical
position while diffusion in the vertical plane shall be provided by wells in
the horizontal position. The Thermoformed Quadratic Residue Diffusor may be
rotated to achieve a variety of patterns that will provide a highly effective
scattering surface.
E
Absorption Coefficients and Noise Reduction Coefficient for the product shall
be measured by an independent, accredited NVLAP facility according to the test
methods as defined by ASTM C 423 and ASTM E 795. Random incidence Absorption
Coefficients for the product in an E-400 mounting shall be as follows:
| 125Hz |
250Hz |
500Hz |
1000Hz |
2000Hz |
4000Hz |
NRC |
| 0.53 |
0.37 |
0.38 |
0.32 |
0.15 |
0.18 |
0.30 |
F
Diffusion Coefficients for the product shall be measured in accordance with the
recommendations of the Audio Engineering Society Working Group SC-04-02 boundary
measurement technique. The directional diffusion coefficient is given by the standard
deviation of the 1/3-octave polar response, for a given angle of incidence, and
normalized by the response of a flat panel of similar size. The average incidence
diffusion coefficients determined at 5° intervals between ± 85°
are listed below at octave-band centers. The mean and standard deviation (SD)
of the 1/3-octave-band coefficients are also tabulated.
| 125Hz |
250Hz |
500Hz |
1000Hz |
2000Hz |
4000Hz |
MEAN |
SD |
| 0.71 |
0.73 |
0.88 |
0.80 |
0.69 |
0.56
|
0.72 |
0.10 |
G
Flame Spread and Smoke Developed shall be tested by an independent, accredited
NVLAP facility according to the test methods as defined by ASTM E 84 and NFPA
255. The Thermoformed Quadratic Residue Diffusor shall have a composite Flame
Spread Rating of less than 25 and a Smoke Development of less than 450.
H
The Thermoformed Quadratic Residue Diffusor shall be supplied in a matte white
finish.
I
The overall dimensions shall be 23-5/8"(H) x 23-5/8"(W) x 4"(D) and weigh no more
than 4 pounds.
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