Pyramidal
Diffusor
A The Pyramidal Diffusor shall be the Golden Pyramid™ as manufactured
by RPG Diffusor Systems, Inc., Upper Marlboro, MD 20774. Tel: 301-249-0044, Fax:
301-249-3912.
B The Pyramidal Diffusor shall be fabricated from Fiberglass Reinforced
Gypsum.
C The Pyramidal Diffusor shall be pyramidal in shape and symmetric along
one axis and asymmetric along the other axis conforming to proportions as defined
by the Golden Mean.
D The Pyramidal Diffusor shall be free from excessive resonance and provide
diffusion in the far field based on the specular reflection principle. The 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 |
| 0.39 |
0.19 |
0.10 |
0.10 |
0.08 |
0.14 |
0.10 |
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 for the three unique orientations.
The mean and standard deviation (SD) of the 1/3-octave-band coefficients are also
tabulated.
| 125Hz |
250Hz |
500Hz |
1000Hz |
2000Hz |
4000Hz |
MEAN |
SD |
| 0.75 |
0.81 |
0.79 |
0.73 |
0.51 |
0.24 |
0.67 |
0.21 |
| 0.77 |
0.80 |
0.72 |
0.78 |
0.60 |
0.35 |
0.69 |
0.16 |
| 0.76 |
0.82 |
0.77 |
0.80 |
0.61 |
0.32 |
0.69 |
0.19 |
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 Pyramidal Diffusor shall have a composite Flame Spread Rating of less
than 25 and a Smoke Development of less than 450.
H The Pyramidal Diffusor shall be supplied in a painted, ceiling white
finish.
I The overall dimensions shall be 23-3/4"(H) x 23-3/4"(W) x 8-1/4"(D) and
weigh no more than 6 pounds.
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