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RPG Diffusor
Systems: Modex Corner
 Small
rooms often exhibit poor low frequency response with significant
emphasis at modal resonances. They also have limited space to
make acoustical improvements. Porous surface absorption is ineffective
at these modal frequencies, because the air motion near walls
and in corners is essentially zero for these long wavelengths.
RPG® research solved this dilemma by developing a unique
membrane system that converts the high sound pressure fluctuations
typically found in corners into selective absorption in the modal
frequency range.
Problem
Small rooms like Project Studios often suffer from low frequency
modal problems. Absorption at these frequencies requires a high
absorption efficiency and significant surface area. Since small
rooms do not offer the needed space, the absorption efficiency
must be optimized.
Solution
RPG® solved this problem by optimizing the absorption efficiency
using a unique internally damped membrane absorber that provides
ideal absorption in the modal frequency range.
Sound (1) strikes the membrane (2) which sympathetically vibrates,
converting the sound pressure to air (3) motion. The air loses
velocity (4) as it moves through the internal absorber and air
cavity. Now you absorb more bass in less space!
Absorption
 Surface
or corner applied porous materials lose efficiency at low frequencies,
because the particle velocity or air movement associated with
long wavelengths is low. The sound pressure, conversely, is at
its maximum. The internally damped membrane in the Modex Corner
exploits this high pressure by converting the pressure fluctuations
into air motion. As the membrane sympathetically vibrates over
a selective low frequency range, determined by its mass and stiffness,
it pushes air through an internal porous layer producing low frequency
absorption. This innovative approach makes it possible for the
Modex Corner to absorb the fundamental and higher harmonic modes
that are often problematic in small rooms.
Impedance Tube Testing
 Random
Incidence absorption coefficient testing has been standardized
by ASTM using the C423 reverberation room method. The frequency
range is 125 Hz to 4,000 Hz. In the United States, most NVLAP
certified reverberation chambers are not accurate below 100 Hz.
Therefore, RPG® also measures its bass traps in compliance
with ASTM C384 using a 2' x 2' impedance tube which is accurate
down to 60 Hz. The graph illustrates the plane wave impedance
tube absorption coefficients for three different samples of the
Modex Corner. The random incidence absorption coefficient for
72ft² or 18 Modex Corner Bass Traps in a Type A mounting
on the floor of the chamber is also shown. The compliance (reciprocal
of stiffness) of each Modex Corner membrane is deliberately made
slightly different to randomly distribute the resonance frequency
over roughly a 10 Hz frequency range. This is evident in the graph
by the fact that Sample 1 is about 7 Hz higher than Samples 2
and 3. The plane wave impedance tube data support the general
low frequency absorption characteristic of the random incidence
data and also indicate the resonance maximum. RPG® has also
developed an in-house transfer function measurement system to
verify the resonance maxima of its low frequency membrane absorbers.
Installation
The Modex Corner can be mounted in any 90° corner between
two walls or a wall and a ceiling. It can be attached directly
to the surfaces using the supplied hook and loop or metal screw
fasteners. If there is no 90° corner available, or if the
corner is not suitable, the Modex Corner can be stacked in a free
standing configuration.
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Material
Description |
Size
(in) |
Order
Code |
Units/Box |
Ship
Wt (lbs) |
Pricing |
|
Bass
trap 40 Hz
#298 Medium Grey
|
2' x 2' x 12.25" |
MDXC1298(40)-2 |
2 |
40 |
$610.00 |
|
Bass
trap 40 Hz
#408 Black |
2' x 2' x 12.25" |
MDXC1408(40)-2 |
2 |
40 |
$665.00 |
|
Bass
trap 40 Hz
#153 Baltic |
2' x 2' x 12.25" |
MDXC1153(40)-2 |
2 |
40 |
$665.00 |
|
Bass
trap 40 Hz
#418 Claret Accent |
2' x 2' x 12.25" |
MDXC1418(40)-2 |
2 |
40 |
$665.00
|
Bass
trap 63 Hz
#298 Medium Grey |
2' x 2' x 12.25" |
MDXC1298(63)-2 |
2 |
40 |
$610.00
|
Bass
trap 63 Hz
#408 Black |
2' x 2' x 12.25" |
MDXC1408(63)-2 |
2 |
40 |
$665.00 |
Bass
trap 63 Hz
#153 Baltic |
2' x 2' x 12.25" |
MDXC1153(63)-2 |
2 |
40 |
$665.00 |
Bass
trap 63 Hz
#418 Claret Accent |
2' x 2' x 12.25" |
MDXC1418(63)-2 |
2 |
40 |
$665.00 |
Bass
trap 80 Hz
#298 Medium Grey |
2' x 2' x 12.25" |
MDXC1298(80)-2 |
2 |
40 |
$610.00 |
Bass
trap 80 Hz
#408 Black |
2' x 2' x 12.25" |
MDXC1408(80)-2 |
2 |
40 |
$665.00 |
Bass
trap 80 Hz
#153 Baltic |
2' x 2' x 12.25" |
MDXC1153(80)-2 |
2 |
40 |
$665.00 |
Bass
trap 80 Hz
#418 Claret Accent |
2' x 2' x 12.25" |
MDXC1418(80)-2 |
2 |
40 |
$665.00 |
Floor
Mounting Stand |
H=number
of units in stack |
MDXCSALH |
1 |
3 |
$39.00 |
Note: Custom colors are available. |
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Northampton, MA 01062 
