Xi-2181/2181F
X-Array™ Install
Bass System
• Unprecedented acoustic output in
a small, lightweight package
• Ring-Mode Decoupling (RMD)™
provides accurate transient detail
• EVX-180B woofers
• Unique rear-hinge rigging
• Flying and non flying configuration
Description
The X-Array
Install™ product line repre-
sents important advancements in concert-
sound-reinforcement technology. The design
goals called for the highest acoustic output
capability with the highest fidelity in light-
weight, compact enclosures that were easy
to array. The development began with a clean
sheet of paper and took an integrated ap-
proach. The individual loudspeaker drivers,
horns, enclosures, rigging hardware and sys-
tem configurations were designed from the
ground up specifically for this high-perfor-
mance application.
The Xi-2181 is a manifolded, vented-box
bass system utilizing two 457-mm (18-in.)
woofers. The two woofers face each other
in a manifold chamber at the center of the
enclosure. This manifolding technique (U.S.
Patent Number 4,733,749) increases the
acoustic loading, resulting in increased low-
frequency efficiency (at slightly above box
tuning) and reduced distortion compared to
conventional direct-radiating designs. The
woofers were designed as part of the Xi-2181
development and represent a step forward
in state-of-the-art loudspeaker design in
terms of high acoustic output with low
distortion and low power compression.
Electro-Voice engineers developed a new
technology dubbed Ring-Mode Decoupling
(RMD
™
) to substantially improve clarity and
intelligibility by reducing both linear and
nonlinear resonance modes that color the
sound.
The low-frequency driver in the Xi-2181 is
the EVX-180B. An improved version of the
industry-standard EVX-180A high-excur-
sion 467-mm (18-in.) woofer that has dis-
tinguished itself as an industry standard for
high-power, low-frequency reproduction.
During the X-Array
™
development, the ther-
mal conduction of the motor was improved
and the suspension was redesigned, giving
the EVX-180B even lower power compres-
sion and a longer mechanical lifetime. In the
Xi-2181, the woofers are manifolded in a
vented enclosure optimized for maximized
output from 37-160 Hz with minimized dis-
tortion.
Ring-Mode Decoupling, (RMD
™
), is a tech-
nique utilized and named by Electro-Voice
to describe a process used to improve sound
quality in loudspeaker systems. RMD
™
of-
fers a solution to a very fundamental prob-
lem. It has long been recognized that two
different loudspeaker systems can sound dif-
ferent even though they both may be equal-
ized to have the same frequency response.
This difference is due to a variety of reso-
nances, or ring modes that color the sound.
Although this ringing may be very low in
level compared to the program material, it is
still audible. The source of these resonances
may be mechanical or acoustical in nature,
or a combination of both. In addition, they
may be linear or nonlinear, resulting in their
character changing with level. Furthermore,
these ring-modes may be aggravated when
multiple loudspeaker enclosures are as-
sembled into arrays. The result is a colora-
tion that decreases intelligibility and clarity,
with the nature of that coloration varying
with level. Often, the listener perceives that
coloration as imbalance in the frequency re-
sponse, and will attempt to electronically
adjust the system to restore the spectral bal-
ance. However this electronic equalization
has the negative effect of changing the pro-
gram material itself.
Ring-Mode Decoupling (RMD
™
) addresses
mechanical resonances with mechanical
solutions, and acoustical resonances with
acoustical solutions. In the Xi-2181 devel-
opment, RMD
™
was applied at every level –
to the individual low-frequency drivers, the
low-frequency enclosure chambers and the
interaction between multiple enclosures. The
design process included, for example, the
driver cone, suspension geometry and mate-
rials, enclosure geometry and materials, ab-
sorptive materials, etc. The result is a dra-
matic improvement in clarity and with a
much more neutral sound (a lack of colora-
tion) with the loudspeaker system maintain-
