JBL 2490-H Brochure

Professional Series

Key Features:

200 watts continuous program
above 250 Hz

Optimized phasing plug design
for low distortion, smooth
response, and wide bandwidth

100 mm (4 in), .08 mm (.003 in)
thickness, titanium diaphragm

76 mm (3 in) throat exit diameter

100 mm (4 in) edgewound
voice coil

The Model 2490H is a unique addi­tion to JBL’s family of professional
quality compression drivers. The
design goal was to provide very high
level sound pressure at low distortion
over the bandwidth of 250 Hz to
above 3 kHz. Extensive computer
modeling, including finite element
analysis and boundary element
analysis, were used to optimize the
magnetic structure, phasing plug,
and diaphragm. This application of
advanced technology has produced a
smaller, lighter weight compression
driver with better performance than
previous high-power midrange
transducers.

A new phasing plug was developed
with an optimized two slit configura­tion A five-to-one compression ratio
produces very low distortion and
smooth, wide bandwidth response.

The new diaphragm design includes
JBL’s exclusive three-dimensional dia­mond pattern surround’ tuned to
reduce fatigue inducing stresses in the
membrane and support structure.

Precision engineering and manufac­turing processes provide controlled
normal and suspension resonance
modes. The diaphragm and suspen­sion use 3 mil pure titanium for
high stiffness and freedom from
breakup modes.

A long voice coil design using high
temperature voice coil former
material and adhesives enable the
2490 to handle high power levels
over extended periods of time.

¹U.S. Patent #4,324,312. Foreign patent pending.

2490H

Midrange
Compression Driver

2490H Midrange Compression Driver

Architectural Specifications:

The compression driver shall consist of a ferrite magnetic structure
with all magnetic assembly parts machined from cast or extruded
billet stock. The phasing plug shall be assembled of concentric horns
to minimize phase cancellations. The diaphragm shall be .08 mm
(.003 in) pure titanium pneumatically drawn to shape. Frequency
response shall be controlled through the use of a three dimensional
suspension structure. The voice coil shall be edgewound aluminum
ribbon of not less than 100 mm (4 in) diameter, operating in a
magnetic field of not less than 1.5 T (15,000 gauss).

Performance specifications of a typical production unit shall be as
follows: Measured sensitivity with a 45 mW input on a 76 mm (3 in)
plane wave tube, averaged from 300 Hz to 4 kHz, shall be at least 123
dB SPL. Measured sensitivity with a 1 W input at 1 m distance on axis
from the mouth of a horn with a Q of 20 averaged in the 2 kHz octave
band shall be at least 114 dB SPL. As an indication of electromechani­cal conversion efficiency, the Bl factor shall be at least 18 Tesla meters.
Frequency response, measured on a terminated tube, shall be flat
within ± 1 dB from 250 Hz to 2.5 kHz. Nominal impedance shall be 8
ohms and power capacity shall be at least 200 watts normal speech or
music program material.

The compression driver shall be the JBL Model 2490. Other drivers
will be considered for equivalency provided that submitted data from
a recognized independent test laboratory verify that the above perfor­mance specifictions are met

Response on JBL 2393 Bi-Radial® Horn

Frequency response of the 2490H coupled to a JBL 2393 Bi-Radial
Horn, measured on-axis at a distance of 1 meter with a l-watt
(2.83 V rms) input in a reflection free environment, with impedance

vs. frequency curve.

Response on Plane-Wave Terminated Tube

®

Frequency response and impedance modulus of model 2490H
coupled to a 76 mm (3 in) diameter terminated plane wave tube
This is the power response of the transducer. (0.6 V rms input).

JBL Professional
8500 Balboa Boulevard, P.O. Box 2200
Northridge, California 91329 U.S.A.

A Harman International Company

10/94 10M
P1149