The
QRD® 734 has proven to be the most popular and versatile
diffusor in the RPG® product line. It’s wide bandwidth,
low cost, and broad selection of finishes make it a logical
choice for music education facilities, recording studios,
worship spaces, auditoriums, theaters, and performing
arts facilities. This one dimensional diffusor is a modular,
computer designed phase grating which produces a directional
hemidisc polar response that can be oriented in any direction.
It also provides low frequency absorption below the design
bandwidth due to the RPG pressure gradient mechanism.
Problem
Interfering reflections that degrade speech intelligibility,
gain before feedback, and music quality can be controlled
by absorption and diffusion. Since commercial surfaces
that provided uniform diffusion over a wide frequency
range and for all angles of incidence were not available,
absorption was used solely to control reflections. This
treatment created ®dead” spaces..
Solution
In 1983, RPG® introduced the first commercial QRD® Diffusor,
based on mathematical number theory. Now a predictable
diffusive surface treatment is readily available.
Diffusion
 Compared
to a flat reflector panel, the QRD® 734 offers significant
diffusion above the diffraction limit of 565Hz, which
is equal to the speed of sound (1130ft/sec) divided
by the 2' dimension of the panel. As the frequency increases
above 565Hz, the graph indicates how the reference reflector
becomes more and more specular, whereas the QRD® 734
provides a uniform diffusivity.
Absorption
The
wooden QRD® 734 or plexiglass Diviewsor™ contribute
minimal absorption. The low cost Kydex® Formedffusor™
is designed to provide additional low frequency absorption.
Installation
The QRD® 734 is typically mounted
on a cleat and secured. For installations that require
a flush
mount the units are framed out much like an opening
for a window.
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Northampton, MA 01062 
