Smooth, powerful, wide-range response within a compact

High Frequency Direct Radiator

enclosure.
Components: 300 mm (12 in), long excursion, low fre- Reproduction above 6 kHz is accomplished by a 36 mm (1.4
quency loudspeaker; 130 mm (5 in) midrange loudspeaker; in) direct radiator. Its 0.74 kg (1% lb) magnetic assembly ana <Y
36 mm (1.4 in) high frequency direct radiator; matched fre- 16 mm (% in) diameter copper voice coil drive a cone and
quency dividing network with front panel controls for mid- center dome with controlled linearity assured by an impre-
range and high frequency output. gnated cloth termination. The voice coil, suspended in a
90” dispersion allows vertical or horizontal placement. magnetic field of 1.5 T (15,000 gauss), is unusually large in
A product of JBL’s long experience and intimate involve- relation to cone size for high efficiency and exceptional tran-
ment with the recording industry. the 43llB is a powerful, yet sient response. The small cone diameter is responsible for
compact monitor loudspeaker system. Its wide-band re- wide, uniform dispersion of high frequency energy: a ring of
production at loudness levels required in professional work dense foam surrounds the moving assembly to damp un-
make the 43llB ideally suited for control room installations, wanted radiation and reflections.
small studios, mixdown facilities, broadcast monitors and
portable playback systems. Frequency Dividing Network

The frequency dividing network installed in the 43llB has

Low Frequency Loudspeaker
been designed and tested to achieve the smoothest possible
Bass material is reproduced by a powerful, long excursion, transitions between component loudspeakers. All network
300 mm (1’2in) loudspeaker having a 75 mm (3 in) diameter components are of the highest quality, Capacitors are non-
edgewound copper ribbon voice coil operating in a mag- inductive, non-polarized types with high AC current
netic field of 1.0 T (10,000 gauss). The magnetic assembly capacity, built expressly for use in dividing networks and in-
weighs 4.7 kg (10% lb); free air resonance is approximately dividually tested for conformity to rigid performance stan-
22 Hz. The surface of the cone is coated with an exclusive dards.
damping formulation that provides the precise mass and
density necessary to optimize bass performance, prevent Enclosure
spurious resonance and provide smooth performance ex-
As with all JBL loudspeaker systems, the component trans-
tending into the midrange region.
ducers, frequency dividing network and enclosure are de-
signed and tested to function as a single, integrated unit.
Midrange ‘Eansducer
The enclosure is solidly constructed of 19 mm (% in) stock
Transition to the mldrange urut 1s made at a crossover fre- throughout with wood-welded joints to prevent unwanted ,>
quency of 1.5 kHz. The 130 mm (5 m) transducer provides resonance. Internal padding absorbs spurious reflections
clarity and freedom from audible dIstortIon, even at the high and standing waves. All components mount directly to the
loudness levels encountered m professional appllcatlons. baffle panel and are removable from the front of the
The transducer IS energized by a magnetic assembly hav- enclosure. A ducted port provides proper acoustical load-
mg a total weight of 0.74 kg (1% lb) and creatmg a magnetic ing of the low frequency loudspeaker.
field of 1.35 T (13,500 gauss). The 22 mm (% m) diameter cop-
per voice co11 drives a 100 mm (4 in) edge-damped cone that
operates as a true piston, provldmg smooth frequency re-
sponse and wide dispersion throughout Its operating range.

2213H
LE252
LE5-10
3112BNetwork notshown

LE25-2
 Adjustable Response Contour Response

he frequency dividing network of the 43llB is provided with

-
front panel controls to allow separate regulation of output in
the 1.5 kHz to 6 kHz range and the region above 6 kHz. Con-
trols are continuously variable from maximum to full off.
With suitable settings of the two controls, the frequency re-
sponse contour of the 4311B can be altered to compensate for
almost any acoustical environment, or to achieve the tonal
balance desired. Control scales are clearly marked so that
special settings can be logged and easily reset when
needed. Frequency resPo”se of the 43llB taken with ‘V-octave band pink Norse. Measured
at1m with a l-watt (“put

Performance Characteristics

The accompanying graph and specifications were com- 35 Hz Output

piled from measurements made under standard laboratory
test conditions. The loudspeaker system was mounted flush
in.the.center of a large, flat baffle in an anechoic environ-
merit; a calibrated condenser microphone was suspended
at a known distance from the sound source, sufficiently far to
be safely out of the near field: and all electronic equipment
was checked and calibrated before tests were run.
The on-axis frequency response of a typical 43 11B does not
vary more than 23 dB from 45 Hz to 15 kHz. Due to the wide-
angle characteristics of the midrange and high frequency
units and their physical orientation, response measured up
to 45” off axis, horizontally or vertically, does not deviate
more than 6 dB from on-axis response at 2 kHz nor more than
10 dB at 8 kHz. The 43llB’s lack of distortion is equally out-
tanding. Distortion is inaudible even at high power levels
b&d at very low frequencies, as shown in the photo at right.
While specifications indicate that the 43 11B has impress-
ive performance characteristics, they cannot convey the full
impact of an extended listening evaluation. Clean, crisp,
wide-range performance, even at very loud levels, power-
ful bass fundamentals without doubling and lifelike voice
projection are qualities found in few loudspeaker systems, This unretouched photo shows the acoustic output of the system when dwen by a
50 W Sine wave slgnal at 35 Hr. A laboratory microphone was used to pick up the
regardless of size or price. When heard from a monitor oc- sound from the 43118 The signal from the microphone was connected directly to
cupying less than 71 litres (2.5 ft3), the effect is little less than a” o~~lll~S~oPe and the trace Photographed.
Sustained Performance at this lntenslty would not be encountered during normal
awesome. “se. A 50 W Sine wave represents a far more dlfflcult job for the loudspeaker than ,ts
rated capactty of 75 W program mawal, particularly in the very low frequency
range Even so. 11can be seen that the 43118 produces an almost perfect sine
wave.
(Note Below 50 Hz, most loudspeaker systems produce substantial dtstortion with
an Input of only a few watts)
 JBL continually engages in research related to product improvement. New mate-
Specifications rials, production methods and design refinements are introduced into existing
Power Capacity’ 75 W continuous program products without notice as a routine expression of that philosophy. For this rea-
son, any current JBL product may differ in some respect from its published de-
Crossover Frequencies 1.5 and 6 kHz scription but will always equal or exceed the original design spectflcations unless
otherwise siated.
Nominal lmpedence 6R
Hugh Frequency 90” horrzontal and vertrcal
Drspersion
Frequency response 45 Hz - 15 kHz t3 dB
Sensitrvrty* 91 dB. 1 W, 1 m (3 3 ft)
42 dB, 1 mW, 30 ft (9 1 m)
Drstortron
M Power, 95 dB Less than 1% third harmonrc
SPU3 m (loft), generation from 100 Hz to 15 kHz
Single Frequency
Finish Textured arav or oiled walnut
Grille Black fabrrc
Dimensions 597 mm x 362 mm x 296 mm deep
23fi in x 14% In x 113/4in deep
Net Weight 21 kg 45 lb
Shipping Weight 24 kg 52~lb

‘Continuous program powerISdefined as 3 dB greater than continuous sine wave

power @MS) It is a conservallve expression of a loudspeaker systems ablllty to
handle normal speech and muw program material
ZMeasured wth Input swept from 500 Hz lo 2 5 kHz with controls set for flattest re-
sponse Unlike many theater type loudspeaker systems that exhlblt sensltlwty
peaks I” the mldrange the JBL Control Monitor provides substantially the same
sensltlwty through the full range of audible frequencies Measured serwtlwty below
500 Hz or above 2 5 kHz may be corwderably greater than that of other systems
with higher sensltlvlty ratings

Professional Division
James B. Lansing Sound, Inc.,
8500 Balboa Boulevard,
Northridge, California 91329U.S.A.