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 20 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.
Features
Pressure zone membrane absorber
Corner mounting
High bass absorption efficiency
Stackable
Wall or free standing mounting
Lightweight
Portable
Modular
Benefits
The proprietary internally damped membrane converts any available
corner into a highly absorptive low frequency absorber
The Modex Corner provides useful low frequency absorption in
wall - wall and wall - ceiling corners that are often unused and
available for acoustical treatment
Corner mounting means you will not have to sacrifice space for
equipment
The Modex Corner is modular and more can be added as needed.
The modules simply stack on top of one another and offer unlimited
opportunity for experimentation and modification
If a 90° corner is not available or if the existing corners
in the room are not right angles, the Modex Corner can be mounted
as a stackable free standing column
The lightweight and portable Corner Bass Trap can be shuttled
between rooms and venues as needed
More product info : http://www.rpginc.com
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