The 4343 represents
an extension of the research and development effort that produced the 4350
Studio Monitor JBL's top system, which uses dual low frequency drivers. This
new monitor accurately reproduces the full range of fundamentals and overtones
in music at sound pressure levels approximating those of an original
performance.
The exceptionally
smooth wide-band reproduction clarity, transient response and low distortion of
the 4343 results from total integration of the components that make up the
four-way system so that each transducer reproduces only that portion of the
audio spectrum for which it is specifically designed Deliberately restricting
the operating bandwidth of the individual drivers results in maximization of
each unit's transient response.
Another benefit of
bandwidth limitation is that each driver operates only in the region of the
audio spectrum through which it exhibits controlled sound distribution, thus a
dispersion pattern for the complete system is achieved which is ideal for
studio use. The passive frequency dividing network supplied with the 4343
controls the acoustic output of all the individual transducers, and may be
switched for bi-amplification.
Features
Accurate smooth
reproduction from 35 to 20,000 Hz, ±3dB
44 dB SPL at 30 feet
with a 1-milliwat input
101 dB SPL at 10
feet at one-half rated power input
Mountable in
vertical or horizontal orientation
Components:
15" low
frequency loudspeaker,
10" midrange
loudspeaker,
High frequency
compression driver with horn/lens assembly and ultra-high frequency transducer
Balance conrols
located behind the removable grille
Rear mounted switch
for bi-amplification or full passive crossover
Oiled walnut or
textured gray enclosure
Ultra-High Frequency
Transducer
Overtones above 9000
Hz are reproduced by a compression driver and diffraction horn specifically
designed for reproduction and dispersion of energy at the extreme high end of
the audio spectrum. The compression driver consist of a 3-1/4 pound magnetic assembly
energized by an Alnico V magnet. The
1,75 inch edgewound aluminum ribbon voice coil, suspended within a field having
a flux density of 16,500 gauss is affixed to a heat resistant support bonded to
a ring diaphragm pneumatically formed of .0022 inch thick aluminum foil. Output
from the diaphragm is directed through the integral diffraction horn, which
produces the unit's wide high frequency dispersion pattern.
High Frequency
Compression Driver
The high frequency
compression driver provides smooth, accurate response and is capable of
delivering the high power output levels required in monitor applications. The
closed magnetic assembly is energized by an
Alnico V magnet, weighs 10 pounds and achieves a flux density of 19,000
gauss in the voice coil gap. A ring of pure silver deposited on the
circumference of the pole piece maintains uniform impedance through the highest
frequencies, extending the bandwidth of the driver. The diaphragm,
pneumatically formed of .002-inch thick aluminum foil stock is driven by a
1,75-inch edgewound aluminum ribbon voice coil. The wavefront emerging from the
diaphragm is directed through the concentric channels of a phasing plug prior
to distribution by the horn/lens assembly.
Horn/Lens Assembly
Output from the high
frequency compression driver is distributed through a controlled pattern by the
horn/lens assembly. The horn is formed of a rigid casting to eliminate spurious
resonance. The exponential taper rate of the horn controls the expansion of the
wavefront providing proper acoustic loading of the driver diaphragm and
determines the vertical dispersion pattern of the assembly. The acoustic lens
functions in a manner analogous to a divergent optical lens. Its 11 plates set
at a precise angle to the enclosure baffle panel, provide controlled
propagation of high frequency acoustic energy in the horizontal plane.
Midrange Loudspeaker
The smooth
performance and instantaneous transient response of the 10-inch midrange
loudspeaker is largely responsible for the outstanding instrumental clarity,
vocal definition and dimensional accuracy of the system. Its closed magnetic
assembly weighing 6-1/2 pounds, concentrates all the energy of an Alnico V
magnet in the voice coil gap. The 3-inch edgewound copper ribbon voice coil is
suspended within a powerful magnetic field having a flux density of 10,000
gauss. The integrally stiffened cone is terminated with an wxclusive JBL ring
compliance that allows long excursion while maintaining linear travel.
Low Frequency
Loudspeaker
The 15-inch low
frequency loudspeaker is mounted in a ported enclosure having an internal
volume of 5,5 cubic feet. The driver features extreme, solid low frequency
reproduction with smooth response well past its crossover frequency. The unit
is energized by a 13-pound magnetic assembly concentrates a magnetic field
having a flux density of 12,000 gauss in the voice coil is hand wound on a heat
resistant support. The support is affixed to a rigid cone having optimum mass
density and rigidity for exceptional transient response and maximum efficiency
with the bandwidth of the driver.
Frequency Dividing
Network
The 4343 is provided
with a high level, passive frequency dividing network for the three transitions
of the system. The network is fitted with a rear-mounted switch and separate
input terminals for bi-amplification. The circuitry has been designed with consideration
for the various performance characteristics of the drivers and their location
on the enclosure baffle panel. The network has been designed for continuous
high power application; capacitors are non-inductive ,non-polarized types with
high AC current capacity and special inductors are used to minimize power
losses within the network. Each inductor is calibrated on a sensitive
electronic bridge and its value set
precisely.
A special circuit
card providing the precise crossover characteristics for bi-amplification of
the 4343 is available for use in the JBL 5233 or 5234 Electronic Frequency
Dividing Network. Conventional electronic networks can be used, but they may
not have the exact frequency and filter slope characteristics required for
optimum performance of the system.
Enclosure
In keeping with
current trends in studio design that encourage creativity, JBL studio monitor
enclosures feature contemporary styling and are offered in two finishes, each
with a complementary grille color. The enclosure, however, contributes much
more than striking appearance. The low frequency loudspeaker is housed in a
chamber having an internal volume of 5,5 cubic feet. The midrange loudspeaker
is enclosed in a separate, isolated sub-chamber having an internal volume of
0,5 cubic feet. The internal volume of the acoustic chambers and physical
configuration of the ducted ports are carefully calibrated to properly load the
low frequency and midrange loudspeakers for optimum bass response and to
control cone excursion, thus minimizing distortion and maximaizing power
handling capacity of the drivers. To eliminate resonance, the enclosure is
constructed of dense 3/4-inch and 1-inch stock with a 15-ply baffle panel; all
joints are carefully interlocked and glued, the back side, top and bottom
panels are lined with acoustic damping material and are each stiffened by
multiple braces glued and screwed to the panel and to the adjacent surfaces of
the enclosure. The baffle section which supports the midrange, high frequency
and ultra-high frequency trasducers may be rotated 90° left or right for
horizontal system instalations.
Specifications
Maximum Power Input
Bi-amplification:
Below 300 Hz : 75
watts continuous sine wave
Above 300 Hz : 75
watts continuous sine wave
Simgle
Amplification: 75 watts continuous sine
wave
Power
Output: 101 dB SPL Measured at 3,0 m (10
ft) in a room volume of 57 m³
(2000 cu ft) with half rated power input
Nominal
Impedance: 8 ohms
Frequency
Response: 35 to 20,000 Hz, ±3 dB
Sensitivity: 93 dB SPL measured at 1m (3,3 ft) with 1-watt
input averaged from 100 to 1000 Hz;
44 dB SPl measured
at 9,1m (30 ft) with 1-milliwatt input averaged from 100 to 1000 Hz
Polar Response: No less than -3 dB at 60° horizontal and 30°
vertical to 16 kHz
Distortion:
1/2 Power, 99 dB
SPL/3,0m : 1% or less third harmonic generation from 35 to 800 hz
Single Frequency :
2% or less third harmonic generation above 800 Hz
Crossover
Frequencies: 300, 1250 and 9500 Hz
Finish: Textured
gray or oiled walnud
Grille: Black fabric with the gray finish; Dark blue
fabric with walnut
Enclosure Volume
Low Frequency
Chamber : 156 litres (5,5 cu ft)
Midrange Chamber :
14 litres (0,5 cu ft)
Enclosure
Dimension: 1050 x 635 x 435 mm (41-3/8 x
25 x 17-1/2 inch)
Net Weight: 79 kg (175 lb)
Accessories for
bi-amplification:
5233 Electronic
Frequency Dividing Network, single channel;
5234 Electronic
Frequency Dividing Network, dual channel;
52-5140 Crossover
Card, required for the low frequency transition of the 4343.