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Model 2420 is a professional quality high frequency com-
pression driver which has an exceptionally wide range and
flat response. It is built to typical JBL standards of precision.
The mathematically determined phasing plug consists of
machined concentric exponential horns to eliminate phase
cancellations. The magnetic assembly is cast and machined
to tolerances considered impractical by industry standards.
The aluminum alloy diaphragm is pneumatically drawn to
shape in order to eliminate stresses that cause fatigue. A
machined ring of pure silver surrounds the pole piece to
counteract the Inductance of the voice co11 at high frequencies.
After manufacture, the frequency response of each driver
IS tested for conformity to rigid performance standards
The 2420 is ideally suited for critical playback systems or
reinforcement systems of the highest quality. Its high efficiency
and power capacity permit great dynamic range. The peakfree response of the 2420 allows greater system gain without acoustic feedback.
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Model 2420-Compression Driver
Architectural Specifications
The compression driver shall consist of an AlnicoV magnet
encased in a cast iron return circuit. All magnetic assembly
parts shall be machined from cast or extruded billet stock.
No stamped or ceramic parts shall be used.The phasing
plug shall be assembled of machined concentric exponential
horns to eliminate phase cancellations, and it shall be further
coupled to a tapered throat, the mouth of which shall be
1 inch in diameter.The back cover shall be cast aluminum
with reinforcing ribs to prevent ringing resonances which
cause peaks in response. The diaphragm shall be 0.002”
aluminum alloy pneumatically drawn to shape to prevent
stressesThe voice coil shall be edgewound aluminum
ribbon of not less than 1.75 inches in diameter, operating in
a magneticfield of notlessthan 19,OOOgaussAn impedance
controlling ring, machined of pure silver, shall be affixed to
the pole piece in order to increase efficiency at high frequen-
cies and maintain flat response.
Performance specrftcatrons of a typrcal productton unit shall
be as follows
Measured
of 1 inch diameter, 3.0 feet long) shall be at least 118 dB. As
an indication of electromechanical conversion efficiency, the
BI factor shall be at least 10.3x 106dynes/abampere.
Frequency response, measured on a terminated tube, shall
be flat within f 5 dB from 800 Hz to 15 kHz. On a 2350
horn, response shall be ?3 dB from 500 Hz to 17 kHz.
Nominal impedance shall be 16 ohms and power capacity
shall be at least 30 Watts normal speech or music program
material.
The compression driver shall be JBL Model 2420 Other
drivers will be considered for equivalency provided that
submitted data from a recognized Independent test laboratory
verify that the above performance specifications are met
sensitivity
at 1 mW on a terminated tube basis (tube
JBL
Professional Products are not intended for household use.
Professional Division
James B. LanSlng Sound,
Inc
,850O
Balboa Boulevard, Northridge, Callfornla 91329
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