JBL 4642A User Manual

4642A Dual 460 mm (18 in) Subwoofer System

Professional Series

Key Features:

c1200 Watts Continuous Pink Noise,

2400 Watts Continuous Program Power Handling

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

c2241H VGCTM Vented Gap Cooled Drivers

–High Sensitivity

–Low Power Compression

–High Maximum-SPL Capability

–Low 2nd and 3rd Harmonic

–Distortion

–Symmetrical Field Geometry SFGTM

–Magnet Structure

–Long Excursion Capability

cApproved by Lucasﬁlm, Ltd. for THX® installations

The JBL Model 4642A is a high quality subwoofer system, featuring an advanced technology 460 mm (18 in), low frequency transducers mounted in a direct radiator, bass-reﬂex enclosure for smooth response to the lowest audible frequencies. The 4642A is ideal for low-frequency augmentation of either analog or digital soundtracks in motion picture theaters and for general sound reinforcement applications.

Transducer:

The 2241H 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.

Through the use of computer-aided magnet optimization and analysis techniques, JBL engineers were able to optimize magnet weight, ﬂux density and ﬁeld saturation, resulting in a 2.6 kg (6.5 lb) reduction in overall driver weight and a signiﬁcant reduction in harmonic distortion. This magnet structure offers much of the weight advantage of rare earth magnet structures without the prohibitive cost, enabling the system to carry a 1200 watt continuous AES pink noise power rating.

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

Speciﬁcations:

TRANSDUCERS: Two JBL Model 2241H 460 mm (18 in) Low

Frequency Transducers

SYSTEM:

Rated Impedance:	4 ohms
Minimum Impedance:	3.2 ohms
POWER HANDLING CAPABILITY:
Continuous Pink Noise1:	1200 Watts
Continuous Program2:	2400 Watts
Peak Power3:	4800 Watts
OUTPUT CAPABILITY:
Axial Sensitivity4:	50 Hz to 500 Hz; 101 dB, 1W @ 1m
	40 Hz to 100 Hz; 100 dB, 1W @ 1m
Power Compression5:
At -10 dB power (120 W):	0.8 dB
At -3 dB power (600 W):	2.6 dB
At rated power (1200 W):	4.3 dB
	Single	Two	Four
	Module	Modules	Modules
Half-Space Reference Efﬁciency6:	5.8%	8.7%	11.6%
Max. Continuous Acoustical
Power Output:	70 W	209 W	557 W
Maximum Continuous SPL @ 1 meter7:	131 dB	136 dB	140 dB
Maximum Peak SPL @ 1 meter7:	137 dB	142 dB	146 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: <2% 3rd harmonic: <2%

System Polarity: EIA Standard. Positive voltage to RED terminal produces forward cone motion.

Input Connectors: Color-coded push terminals

Net Weight: 98 kg (216 lbs.)

Shipping Weight: 109 kg (240 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: 506 liters (18 cu. ft)

Dimensions: 762 mm x 1219 mm x 610 mm

H x W x D 30 in x 48 in x 24 in

See footnotes on back

c 4642A Dual 460 mm (18 in) Subwoofer System

The 100 mm (4 in) voice coil beneﬁts from a new winding technique which offers greater thermal stability with increased power handling. All elements of the cone, voice coil and suspension system have been carefully optimized and controlled to ensure smooth high frequency response.

The magnet structure and compliance allow for long peak-to-peak excursions without damage to the speaker. 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 506 liters (18 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 4642A 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.

1AES continuous pink noise (25 - 250 Hz), 2 hours duration.

2Continuous 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.

3Peak power is deﬁned as 6 dB greater than AES continuous pink noise, reﬂecting the

6 dB crest factor contained in the pink noise signal.

4Averaged half-space (2p). Quarter-space (1p, wall/ﬂoor junction placement) is 6 dB higher.

5Power 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.

6Based upon speciﬁed half-space 40 Hz to 100 Hz sensitivity; 50 Hz to 500 Hz reference efﬁciency is higher.

7Per industry practice, maximum long-term SPL is a calculation that references half-space

1W/1m sensitivity, scaled by the long-term continuous power rating.

8Based upon speciﬁed sensitivity, 40 Hz to 100 Hz.

9100 watt sine wave input, averaged from 40 Hz to 100 Hz.

4642A 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. 1p (upper curve) and 2p (lower curve) conditions.

4642A frequency response and impedance (bottom curve), 1 watt at 1 meter, with 150 Hz Linkwitz-Riley 4th order low-pass ﬁlter measured under 4p ground plane conditions. 1p (upper curve) and 2p (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.


JBL Professional
8500 Balboa Boulevard, P.O. Box 2200
Northridge, California 91329 U.S.A.		SS 4642A
		CRP 10M
A Harman International Company		10/98