JBL 4645C User Manual

4645C

Single 460 mm (18 in)
Subwoofer System

Key Features:

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800 Watts Continuous Pink Noise,
1600 Watts Continuous Program
Power Handling

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Usable response to 22 Hz (-10 dB,
no EQ), flat to 22 Hz (-3 dB) with
External EQ

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2242H SVGTMSuper Vented Gap
Cooled Driver
– High Sensitivity
– Minimal Power Compression
– Highest Maximum-SPL Capability
– Extremely Low 2nd and 3rd

– Harmonic Distortion

– Symmetrical Field Geometry SFG

TM

– Magnet Structure

– Extended Excursion Capability

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Approved by Lucasfilm, Ltd. for
THX®installations

The JBL Model 4645C is a high
quality subwoofer system, featuring an
advanced technology 460 mm (18 in),
low frequency transducer mounted in
a direct radiator, bass-reflex enclosure
for smooth response to the lowest
audible frequencies. The 4645C is
ideal for low-frequency augmentation
of either analog or digital soundtracks
in motion picture theaters and for
general sound reinforcement
applications.

Transducer:

The 2242H transducer utilizes the
patented Vented Gap Cooling (VGC)
process*, which pumps air through the
magnetic gap and directly over and
around the voice coil, providing
immediate heat transfer and a
reduction in operating temperature.
This increases power handling while
reducing power compression.

The 2242H utilizes a rugged 100
mm (4 in) diameter voice coil and
incorporates a large motor structure
with a pole piece that extends both
above and below the top plate to
improve gap flux symmetry and
increase thermal conductivity. This
magnet structure and the use of a
voice coil with one-third more
exposed area than in former designs,
provides the 2242H with very effective
heat sinking, enabling the system to
carry an 800 watt continuous AES pink
noise power rating.

*U.S. Patent #5,042,072. Foreign Patents Pending.

Specifications:

TRANSDUCER: JBL Model 2242H 460 mm (18 in) Low Frequency

Transducer

SYSTEM:

Rated Impedance: 8 ohms

Minimum Impedance: 7.2 ohms

POWER HANDLING CAPABILITY:

Continuous Pink Noise1: 800 watts

Continuous Program2: 1600 watts

Peak Power3: 3200 watts

OUTPUT CAPABILITY:

Axial Sensitivity4: 50 Hz to 500 Hz; 99 dB, 1W @ 1m

40 Hz to 100 Hz; 97 dB, 1W @ 1m

Power Compression5:
At -10 dB power (80 W): 0.6 dB
At -3 dB power (400 W): 2.0 dB

At rated power (800 W): 3.3 dB

Single Two Four Eight
Module Modules Modules Modules

Half-Space Reference Efficiency6: 4% 8% 12% 16%

Max. Continuous Acoustical

Power Output: 32 W 128 W 384 W 1024 W

Maximum Continuous SPL @ 1 meter7: 126 dB 132 dB 137 dB 141 dB

Maximum Peak SPL @ 1 meter7: 132 dB 138 dB 143 dB 147 dB

FREQUENCY RESPONSE8: Lower Frequency Limits (no EQ):

-10 dB: 22 Hz

-3 dB: 35 Hz
Lower Frequency Limits (with EQ):

-10 dB: 20 Hz

-3 dB: 22 Hz

Recommended Crossover Frequencies: High-pass: 20 Hz, 12 dB/octave or greater

Low-pass: 80 Hz to 150 Hz, 12 dB/octave or greater

Distortion9:

2nd harmonic: <0.6%

3rd harmonic: <0.8%

System Polarity: EIA Standard. Positive voltage to RED terminal

produces forward cone motion.

Input Connectors: Color-coded push terminals

Net Weight: 63 kg (138 lbs.)

Shipping Weight: 69 kg (151 lbs.)

ENCLOSURE:

Materials and Finish: 19 mm (¾ in) particle board with 25 mm (1 in) baffle

and back panel. Extensive bracing on all panels

Enclosure Tuning Frequency: 25 Hz

Net Internal Volume: 225 liters (8 cu. ft)

Dimensions: 1010 mm x 674 mm x 450 mm

H x W x D 39¾ in x 26½ in x 17¾ in

See footnotes on back ☞

Professional Series

JBL Professional
8500 Balboa Boulevard, P.O. Box 2200
Northridge, California 91329 U.S.A.

A Harman International Company

SS 4645C
CRP 10M
3/99

䉴 4645C Single 460 mm (18 in) Subwoofer System

4645C frequency response, 1 watt at 1 meter, with 150 Hz Linkwitz­Riley 4th order low-pass filter and 2nd order high-pass filter at 25 Hz
with Q=2. 1␲ (upper curve) and 2␲ (lower curve) conditions.

4645C frequency response and impedance (bottom curve), 1 watt at
1 meter, with 150 Hz Linkwitz-Riley 4th order low-pass filter
measured under 4␲ ground plane conditions. 1␲ (upper curve) and
2␲ (center curve) loading condition predictions also shown.

JBL continually engages in research related to product improvement. New materials,
production methods, and design refinements are introduced into existing products
without notice as a routine expression of that philosophy. For this reason, any current
JBL product may differ in some respect from its published description, but will always
equal or exceed the original design specifications unless otherwise stated.

The magnet structure and compliance allow for long
peak-to-peak excursions without damage to the speaker.
The pole piece incorporates a shorted copper ring while
functioning as a shorted secondary turn, with the voice
coil acting as the primary winding. The benefits are a
reduction of third harmonic distortion from magnetic flux
modulation and a reduced inductive component of the
voice coil impedance, for improved transient response.
Symmetrical Field Geometry (SFG) minimizes second
harmonic distortion.

Enclosure:

The enclosure is constructed of dense stock and is
extensively braced on all panels. It has a net internal
volume of 225 liters (8 cu. ft.) and is tuned to 25 Hz with
a very large port to minimize port compression and to
reduce distortion due to turbulent air flow.

Frequency Response:

The 4645C features high sensitivity. It is intended for
use as a subwoofer with a low-pass filter and appropriate
high-pass filtering for protection and equalization.

Note: Drawing not to scale. All dimensions are reference
only.

1

AES continuous pink noise (25 - 250 Hz), 2 hours duration.

2

Continuous program power is defined as 3 dB greater than AES continuous pink noise
and is a conservative expression of the transducer’s ability to handle normal music
program material.

3

Peak power is defined as 6 dB greater than AES continuous pink noise, reflecting the
6 dB crest factor contained in the pink noise signal.

4

Averaged half-space (2␲). Quarter-space (1␲, wall/floor junction placement) is 6 dB
higher.

5

Power compression is the sensitivity loss at the specified power, measured from 50 Hz
to 500 Hz, after a 5 minute AES standard (50 to 500 Hz) signal at the specified power.

6

Based upon specified half-space 40 Hz to 100 Hz sensitivity; 50 Hz to 500 Hz reference
efficiency is higher.

7

Per industry practice, maximum long-term SPL is a calculation that references half-space
1W/1m sensitivity, scaled by the long-term continuous power rating.

8

Based upon specified sensitivity, 40 Hz to 100 Hz.

9

100 watt sine wave input, averaged from 40 Hz to 100 Hz.