JBL 4311 Brochure

Smooth, powerful,

wide-range

response within a

compact enclosure.
Components: 300-mm (1 Sin), long excursion, low

frequency loudspeaker; 130-mm (Sin) midrange
loudspeaker; 36mm (1.4-in) high frequency direct
radiator; matched frequency dividing network with
front panel controls for midrange

and

high fre-

quency output.
90’ dispersion allows vertical or horizontal place-

ment.

A product of JBL’s long experience and intimate
involvement with the recording industry, the 4311 is a
powerful, yet compact, monitor loudspeaker system. Its
wide-band reproduction at loudness levels required in
professional work make the 4311 ideally suited for con­trol room installations, small studios, mixdown facilities,
broadcast monitors and portable playback systems.

Low Frequency Loudspeaker

Bass material is reproduced by a powerful, long excur­sion, 300-mm (12-in) loudspeaker having a 76-mm
(3-in) diameter edgewound copper ribbon voice coil
operating in a magnetic field of 1 T (10,000 gauss). The
magnetic assembly, energized by an Alnico V magnet,
weighs 3 kg (6.5 lb); free air resonance is approximately
22 Hz. The surface of the cone is coated with an exclusive
damping formulation that provides the precise mass
and density necessary to optimize bass performance,
prevent spurious resonance and provide smooth per­formance extending into the midrange region.

Midrange Transducer

Transition to the midrange unit is made at a crossover
frequency of 1.5 kHz. The 130-mm (5-in) transducer
provides clarity and freedom from audible distortion,

even at the high loudness levels encountered in profes­sional applications. The transducer is energized by an
Alnico V magnet housed in a closed assembly having a
total weight of 1.25 kg (2.75 lb) and creating a magnetic
field of 1.65 T (16,500 gauss). The 22-mm (7/&in) diame­ter copper voice coil drives a loo-mm (4-in) edge-

damped cone that operates as a true piston, providing

smooth frequency response and wide dispersion
throughout its operating range.

High

Frequency Direct Radiator

Reproduction above 6 kHz is accomplished by a 36-mr
(1.4-in) direct radiator. Its 0.7.kg (1.6 lb) magnetic d
assembly and 16-mm (5/&in) diameter copper voice
coil drive a cone and center dome with controlled
linearity assured by an impregnated cloth termination.
The voice coil, suspended in a magnetic field of 1.5 T
(15,000 gauss), is unusually large in relation to cone size
for high efficiency and exceptional transient response.
The small cone diameter is responsible for wide, uniform
dispersion of high frequency energy; a ring of dense
foam surrounds the moving assembly to damp un-

wanted radiation and reflections.

Frequency Dividing Network

The frequency dividing network installed in the 4311 has
been designed and tested to achieve the smoothest pos­sible transitions between component loudspeakers. All
network components are of the highest quality. Ca­pacitors are non-inductive, non-polarized types with
high AC current capacity, built expressly for use in divid­ing networks and individually tested for conformity to
rigid performance standards.

Enclosure

As with all JBL loudspeaker systems, the component
transducers, frequency dividing network and enclosure

are designed and tested to function as a single, inte­grated unit. The enclosure is solidly constructed of

d

19-mm (3/4-in) stock throughout with wood-welded

joints to prevent unwanted resonance. Internal padding

absorbs spurious reflections and standing waves. All
components mount directly to the baffle panel and are
removable from the front of the enclosure. Aducted port
provides proper acoustical loading of the low frequency

2213
LE 25
LE 5-2
3112-A Network not shown