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Extremely wide-band linear response characteristics,
high acoustic output, controlled dispersion pattern.
Components: two 380 mm (15 in) low frequency
loudspeakers, 300 mm (12 in) midrange loudspeaker,
high frequency compression driver with horn/lens
assembly, diffraction horn ultra-high frequency
driver.
Rigidly constructed enclosure provides separate
acoustic loading of the low frequency and midrange
loudspeakers and provides for mirror image
mounting of the high frequency and ultra-high
frequency drivers.
The 4350B Studio Monitor
The JBL 4350B is the result of an engineering study
undertaken to create, regardless of cost, the optimum
studio loudspeaker for monitoring recording sessions and
for final mixdown of master tapes A four-way system
designed for bi-ampldicahon, it achieves inherently
smooth reproduction within three dB from 30 Hz to 20 kHz.
controlled high frequency dispersion, and exceptional
transient performance. In addition, the 4350 is capable of
wide dynamic range with low distortion, and of the high
acoustic output required for precise reproduction of the
original sounds. It is an indispensable tool, not only for
mastering and mixdown. but also for subjective analysis
of the entire studio recording and reproducing complex.
Midrange Loudspeaker
Music fundamentals lying in the region between 250
Hz and 1.1 kHz are reproduced by a 300 mm (12 in)
loudspeaker housed in a sealed sub-chamber and
driven by a 100 mm (4 in) edgewound copper ribbon
voice coil. The SFG design of the magnetic structure
results in exceptionally low levels of second harmonic
distortion. The magnetic assembly weighs 8.5 kg (18%
lb) and produces a flux density of 1.2 T (12,000 gauss)
in the voice coil gap. The driver achieves high
acoustic efficiency and effortless reproduction, even
at extreme volume levels.
High Frequency Compression Driver
Reproduction from 1.1 to 9 kHz is accomplished by a
massive compression driver energized by a magnetic
assembly weighing 11 kg (23.75 lb). Its 100 mm (4 in)
edgewound aluminum ribbon voice coil, suspended
in a magnetic field of 1.8 T (18,000 gauss), drives a
diaphragm pneumatically drawn to shape from 0.08
mm (0.003 in) aluminum alloy. Proper phasing of the
wavefront is assured by use of a phasing plug. The
combination of an extremely powerful, efficient
magnetic assembly, edgewound voice coil and large
yet lightweight diaphragm results in exceptional
transient response and dynamic range.
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Bi-ampltiication
The two low frequency loudspeakers are driven
independently of the other components in the system This
allows the utilization of two moderately powered
amplifiers rather than a single, large model, and lessens
the possibility of distortion, even at high volume levels.
Low Frequency Loudspeakers
Two 380 mm (15 in) low frequency loudspeakers.
mounted in a ported enclosure, provide accurate
reproduction and high power handling capacity at
very low frequencies The use of two drivers results in a
3-dB increase m acoustic output and allows twice the
power input to the low frequency section. Each
loudspeaker is driven by a 100 mm (4 in) diameter
voice coil. fabricated of edgewound copper ribbon
wire, and an 8 5 kg (18% lb) magnetic assembly with
a flux density of 1.2 T (12,000 gauss). The magnetic
structure incorporates JBL’s unique Symmetrical Field
Geometry (SFG) design that reduces second
harmonic distortion to inconsequential levels. A
compliant cone termination allows long excursions
and damps spurious reflections traveling within the
cone material.
Horn/Lens Assembly
High frequency output is distributed by an exponentia, >
horn combined with a slant-plate acoustic lens. The rigid
horn casting couples the output of the high frequency
driver to the acoustic lens without adding audible
resonance or distortion. The 11 plates of the lens, set at an
angle of 380. operate in a manner analogous to a
divergent optical lens, providing controlled propagation
of high frequency acoustic energy.
Ultra-High Frequency Transducer
The highest octave of the audio spectrum is reproduced
2231H -
240s
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by a compression driver specifically designed for
ultra-high frequency reproduction and dispersion. Its
1.5 kg (3.25 lb) magnetic assembly develops a flux
density of 1.65 T (16,500 gauss) and drives a 45 mm
(1.75 in) edgewound aluminum ribbon voice coil. The
driver utilizes a ring diaphragm pneumatically formed of
0.06 mm (0.0022 in) anodized aluminum foil stock. Output
is directed through a diffraction horn providing 90’
dispersion in the plane perpendicular to the diffraction
slot while restricting dispersion in the vertical plane to
approximately 40? The device maintains smooth
response within 3 dB to 20 kHz.
Frequency Dividing Network
The low frequency loudspeakers operate to 250 Hz and
require an attenuation rate of 12 dB per octave below
and above the crossover frequency. Transition may be
accomplished with a JBL 5233 (single channel) or 5234
(dual channel) Electronic Frequency Dividing Network
or with one of several electronic crossovers or filtering
devices commercially available.
The midrange, high frequency, and ultra-high
frequency drivers are regulated by a high-level passive
network of the L-C type specifically designed and tested
for operation with the transducers of the system.
Transition between the midrange loudspeaker and the
high frequency compression driver occurs at 1.1. kHz at
the rate of 12 dB per octave. The compression driver
operates to 9 kHz with high frequency attenuation
accomplished by the inherent performance
characteristics of the unit. At 9 kHz, the ultra-high
&.-
frequency driver is brought into operation at 18 dB per
octave. A level control is provided.
mounted flush in the center of a large, flat baffle in an
anechoic environment. A calibrated condenser
microphone was suspended at a measured distance
from the sound source, sufficiently out of the near field.
All associated electronic equipment was checked and
calibrated before tests were run.
Response
Enclosure
Components of the 4350B are housed in a rigid
enclosure incorporating two acoustic chambers The
two low frequency loudspeakers are housed in a bass
reflex chamber which has an internal volume of 265
litres (9.5 IV) Proper loading to 25 Hz is accomplished
by a distributed port consisting of six openings The
midrange loudspeaker is mounted in a second, sealed
sub-chamber measuring 45 litres (1.6 ft3) in volume and
designed to prevent acoustical interaction with the low
frequency drivers The sub-chamber also attenuates
output of the midrange unit below 200 Hz, thus reducing
unwanted peaks in total system response. The enclosure
is constructed of 19 mm
rigidity with minimum weight. All Joints are lock-mitered
and glued, panels are heavily braced to prevent
unwanted resonances, and interior surfaces are
padded to damp spurious reflections and standing
waves within the acoustical chambers. All components
mount directly to the baffle panel and are accessible
from the front of the enclosure
Test Parameters
T
Ll
The accompanymg graphs and specifications were
compiled from measurements made under standard
laboratory test conditions The loudspeaker system was
(31’4
in) stock for maximum
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Specifications
Maximum Power Input
Below 250 Hz 200 watts continuous sine wave
Above 250 Hz 100 watts continuous sine wave
Nominal Impedance
Below 250 Hz
Above 250 Hz
Power Output’
Frequency Response
Sine wave, on-axis
l/3-octave band
(500 Hz reference)
Polar Response
Sensitivity’
Distortion
r/z power, 108 dB SPL. 1% or less third harmonic from
3 m (10 ft). 35 Hz to 1.2 kHz
single frequency
l/10 power, 101 dB SPL, 0.6% or less third harmonic
3 m (10 ft),
single frequency
Crossover Frequencies
Low 250 Hz electronrc. 12 dB/octave
Mid 1.1 kHz
High 9 kHz
Finish
Grille
at 4C?
at 80
40
80
110 dB SPL pink noise measured
at 3 m (10 ft) in a room volume of
57 m’ (2000 ft’) with r/z rated power
input (-3 db)
126 dB SPL approximate program
peak output measured at 3 m
(10 ft) with r/z rated power input
(average)
30 Hz-20 kHz, -3 dB
-3 dB at 31.5 Hz. +2 dB at 1 kHz,
+2 dB at 16.5 kHz
No less than -3 dB at 60“ horizontal
and 30’ vertical to 12 kHz
95 5 dB SPL. lW, lm (3.3 ft)
3% or less third harmonic from
1.2 to 5 kHz
generation from 1.2 to 5 kHz
Textured gray or oiled walnut
Black fabric with the gray finish
Dark blue fabric with walnut
Enclosure Volume
Low Frequency
Hugh Frequency
Drmensrons
Net Weight
Shrpprng Werght
Accessones
265 lrtres (9 5 ftl)
45 htres (1 6 ft’)
890 mm x 1210 mm x 510 mm deep i/
35 rn x 47% rn x 20 rn deep
118 kg 260 lb
138 kg
303 lb
5233 Electronrc Frequency Drvtdtng
Network, srngle channel
5234 Electronrc Frequency Drvrdrng
Network, dual channel
52-5140 crossover card for
5233 or 5234 (one card requrred par
channel)
‘Power
output measured wth a B&K
‘Unlike many theater type” loudspeaker systems that exhlblt sensmwty
peaks I” the mldrange region the 4350 provides substantially the same
sens~t~wty through the full range of audible frequencies Measured
sensltlwty below 500 Hz or above 2 kHr may be consIderably greater than
that of other systems which claim higher sensltwty ratings
Caution
Sound pressure levels produced by the 4350 may cause
permanent hearing loss The suggested maximum exposure IS 115 dBA for
no more than 15 minutes (U S Department of Labor Bulletin #334)
JBL continually engages I” research related to product improvement New
materials, productlo” methods and design refinements are Introduced
Into exlsllng products wlthout notlce as a routine expressm” of that phllosophy For this reason any current JBL product may differ I” some respect from
Its publlshed descrlptlon but will always equal or exceed the orIgInal design
speclflcatlons unless otherwse stated
Impulse
Prec~smn Sound Level Meter
Professional Divtsion
James B. Lansing Sound, Inc..
8500 Balboa Boulevard,
Northridge, California 91329
U. S. A.
8343508/S-SO PrInted ,n U S.A.
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