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EVX-180B
18 Inch Low-Frequency
Reproducer
General Product Description
The EVX-180B low-frequency transducer is designed for professional
sound reinforcement or studio monitoring applications that require
maximum output with low distortion.
The EVX-180B woofer provides unprecedented power capacity, linearity
and excursion, made possible by the HeatWick
®
total-thermal-engineering design. The proprietary HeatWick design
actually “wicks” heat away from the voice coil, significantly increasing
power handling and long-term reliability. A special frame extension and
elongated pole piece provide a metal surface with close proximity to
the entire length of the voice coil, providing a major heat-transfer path.
Also, the 100-mm (4-in.) diameter voice coil is longer than conventional
medium efficiency woofers to give additional power handling and virtually
eliminate dynamic-range power compression.
Additionally, a Flux Demodulation Device (FDD™) reduces distortion
in the critical mid-band by providing a “short circuit” effect to prevent
amplifier-signal modulation of the static magnetic field.
A ribbed, Kevlar
®
fiber composite cone with an extremely high
stiffness-to-weight ratio and exceptional strength gives the EVX-180B
increased resistance to cone collapse and deformation, without
sacrificing efficiency.
Architects’ and Engineers’ Specifications
The low-frequency transducer shall have a nominal diameter of 460
mm (18 in.), overall depth not greater than 198 mm (7.92 in.), and weigh
no more than 11 kg (25 lb). The frame shall be made of die-cast aluminum
to resist deformation. The magnetic assembly shall have an extended
pole piece to reduce inductive variances with excursion, and provide a
symmetrical magnetic field at the voice-coil gap. Two aluminum rings
shall encircle the pole piece above and below the magnetic gap, and
shall have internal diameters concentric with the internal diameter of
the steel top plate. The upper ring shall be part of the loudspeaker
frame. Both rings act to reduce flux modulation and provide a heat
transfer path from the outer diameter of the voice coil.
The voice coil shall be 100 mm (4 in.) in diameter and 20 mm (0.8 in.)
in winding length, and shall be made of edge-wound aluminum ribbon.
When centered in the magnetic gap, the voice coil shall produce a
force of not less than 21.9 newtons (tesla-ampere-meters) with a dc
current of 1 ampere. Performance specifications of a typical production
unit shall be as follows: measured sensitivity (SPL at 1 m (3.3 ft) with
1-watt input, 100 to 800 Hz pink noise) shall be at least 96 dB. The
half-space reference efficiency shall be at least 3.0%. The usable
frequency response shall be 20 Hz to 2,000 Hz, and the nominal
impedance shall be 8 ohms. The rated power for the loudspeaker shall
be 1,000 watts continuous power.
The low-frequency transducer shall be the Electro- Voice
®
EVX-180B.
Directional Characteristics
The directional characteristics of the EVX-180B in the TL3512 256-liter
(9-ft³) vented enclosure were measured by running a set of polar
responses in EV’s large anechoic chamber. The test signal was
octave-band-limited pseudo-random pink noise centered at the ISO
standard frequencies.
The curves show horizontal (side-to-side) dispersion when the
enclosure’s long axis is vertical. The vertical (up-and-down) polar
responses deviate only slightly from the horizontal responses due to
box geometry. Typical data is provided in Figures 1 and 2, which indicate
6-dB-down beamwidth versus frequency and directivity factor,
respectively, for an EVX-180B in the TL3512 enclosure.
Electrical Connections
The EVX-180B is fitted with a pair of chrome-plated, frame-mounted
connectors with color-coded ends. Electrical connection is made by
pushing down, inserting wire completely through the rectangular slot
and releasing pressure. One conductor of #9 AWG stranded, #8 AWG
solid, a pair of twisted #15 AWG stranded or a pair of #14 AWG solid
conductors will fit. A positive electrical signal applied to the red (+)
terminal will displace the cone away from the magnet, thus producing a
positive acoustic pressure.
Recommended Enclosures
The most extended bass, lowest distortion and best control is usually
realized in properly designed vented enclosures. In such designs, the
vent, or port, actually provides the lowest octave of output. The vent is
driven to full acoustic output by a relatively small motion of the speaker
cone itself, acting through the air contained within the enclosure. The
excursion of the EVX-180B at these frequencies is much reduced
compared to sealed or open-back enclosures, directly reducing harmonic
distortion and the possibility of speaker “bottoming.” The maximum output
is limited by either: (1) the long-term thermal power-handling capacity
or (2) the speaker’s maximum cone-excursion capability, whichever
occurs first.-excursion capability, whichever occurs first.
Figure 1. Beamwidth vs. Frequency