JL Audio G4500 User Manual

OWNER’S MANUAL

Thank you for purchasing a JL Audio amplifier for

your automotive sound system.

Your amplifier has been designed and manufactured to exacting

standards in order to ensure years of musical enjoyment in your vehicle.

For maximum performance, we highly recommend that you have

your new amplifier installed by an authorized JL Audio dealer. Your

authorized dealer has the training, expertise and installation equipment

to ensure optimum performance from this product. Should you

decide to install the amplifier yourself, please take the time

to read this manual thoroughly so as to familiarize yourself

with its installation requirements and setup procedures.

If you have any questions regarding the instructions in this

manual or any aspect of your amplifier’s operation, please contact your

authorized JL Audio dealer for assistance. If you need further assistance,

please call the JL Audio Technical Support Department

at [phone] during business hours.

PROTECT YOUR HEARING!

Input Voltage

Selection

(pg. 6)

Channels 3 & 4

Preamp Inp ut Jacks

(pg. 6)

Channels 1 & 2

Preamp Inp ut Jacks

(pg. 6)

Left & Right

Preamp Out put

Jacks

(pg. 8)

Ch. 3 & 4

Bass Boost

On/Off Swi tch

(pg. 8)

Pre-Out Signal

Selection Swi tch

(pg. 8)

Power
Status

Indicator

(pg. 10)

Jack for
Remote Bass
Control K nob

(pg. 8)

Ch. 3 & 4

Input Select ion

Switch
(pg. 6)

Ch. 1 & 2 Filte r

Frequenc y

Selector

(pg. 7)

Ch. 1 & 2 Inp ut

Sensitivity

Control

(pg. 6)

Protectio n Status

Indicator

(pg. 10)

Ch. 1 & 2

Filter Mode

Selection

(pg. 7)

Ch. 3 & 4

Filter Mode

Selection

(pg. 7)

Ch. 3 & 4

Input Sensitiv ity

Control

(pg. 6)

Ch. 3 & 4

Filter Frequen cy

Selector

(pg. 7)

Remote Turn-On

Connector

(pg. 5)

Chassis Ground

Connector

(pg. 5)

+12 V Power

Connector

(pg. 4)

Channels 3 & 4

Speaker Outputs

(pg. 8)

Channels 1 & 2

Speaker Outputs

(pg. 8)

We value you as a long-term customer. For
that reason, we urge you to practice restraint in
the operation of this product so as not to damage
your hearing and that of others in your vehicle.
Studies have shown that continuous exposure to
high sound pressure levels can lead to permanent
(irreparable) hearing loss. This and all other
high-power amplifiers are capable of producing
such high sound pressure levels when connected

to a speaker system. Please limit your continuous

exposure to high volume levels.

While driving, operate your audio system in
a manner that still allows you to hear necessary
noises to operate your vehicle safely (horns,
sirens, etc.).

SERIAL NUMBER

In the event that your amplifier requires
service or is ever stolen, you will need to have

a record of the product’s serial number. Please

take the time to enter that number in the space
provided below. The serial number can be found
on the bottom panel of the amplifier and on the
amplifier packaging.

Serial Number:

INSTALLATION APPLICATIONS

This amplifier is designed for operation in
vehicles with 12 volt, negative-ground electrical
systems. Use of this product in vehicles with
positive ground and/or voltages other than 12V
may result in damage to the product and will void
th e w ar ran ty.

This product is not certified or approved for
use in aircraft.

Do not attempt to “bridge” the outputs of this

amplifier with the outputs of a second amplifier,
including an identical one.

PLANNING YOUR INSTALLATION

It is important that you take the time to read
this manual and that you plan out your
installation carefully. The following are some
considerations that you must take into account
when planning your installation.

Cooling Efficiency Considerations:

The outer shell of your JL Audio amplifier
is designed to remove heat from the amplifier
circuitry. For optimum cooling performance,
this outer shell should be exposed to as large a
volume of air as possible. Enclosing the amplifier
in a small, poorly ventilated chamber can
lead to excessive heat build-up and degraded
performance. If an installation calls for an
enclosure around the amplifier, we recommend
that this enclosure be ventilated with the aid
of a fan. In normal applications, fan-cooling
is not necessary.

Mounting the amplifier upside down is
strongly discouraged.

If mounting the amplifier under a seat,
make sure there is at least 1 inch (2.5 cm) of
space above the amplifier’s outer shell to permit
proper cooling.

Safety Considerations:

Your amplifier needs to be installed in a dry,
well-ventilated environment and in a manner
which does not interfere with your vehicle’s safety
equipment (air bags, seat belt systems, ABS brake
systems, etc.). You should also take the time to
securely mount the amplifier so that it does not
come loose in the event of a collision or a sudden
jolt to the vehicle.

Stupid Mistakes to Avoid

• Check before drilling any holes in your vehicle

to make sure that you will not be drilling
through a gas tank, brake line, wiring harness or
other vital vehicle system.

• Do not run system wiring outside or underneath

the vehicle. This is an extremely dangerous
practice which can result in severe damage to
your vehicle and person.

• Protect all system wires from sharp metal

edges and wear by carefully routing them,
tying them down and using grommets and
loom where appropriate.

• Do not mount the amplifier in the engine

2 JL AUDIO G4500 JL AUDIO G4500 3

compartment, under the vehicle, on the roof
or in any other area that will expose the
amplifier circuitry to the elements.

PRODUCT DESCRIPTION

The JL Audio G4500 is a four-channel,
full-range audio amplifier utilizing patented
Absolute Symmetry™ Class A/B technology
for all channels.

The G4500 can be operated with a wide variety
of source units and system configurations.

TYPICAL INSTALLATION SEQUENCE

The following represents the sequence
for a typical amplifier installation, using an
aftermarket source unit or OEM Interface
processor (like the CleanSweep CL441dsp).
Additional steps and different procedures may
be required in some applications. If you have
any questions, please contact your authorized
JL Audio dealer for assistance.

1) Disconnect the negative battery post

connection and secure the disconnected cable
to prevent accidental re-connection during
installation. This step is not optional.

2) Run power wire (minimum 8 AWG) from the

battery location to the amplifier mounting
location, taking care to route it in such a
way that it will not be damaged and will not
interfere with vehicle operation. Use 4 AWG
or larger power wire and a power distribution
block if additional amplifiers are being
installed with the G4500.

3) Connect power wire to the positive battery

post. Fuse the wire with an appropriate fuse
block (and connectors) within 18 inches (45
cm) wire length of the positive battery post.

This fuse is essential to protect the vehicle.
Do not install the fuse until the power wire
has been securely connected to the amplifier.

4) Run signal cables and remote turn-on wire

from the source unit to the final amplifier
mounting location.

5) Run speaker cables from the speaker systems

to the amplifier mounting location.

6) Find a good, solid metal grounding point

close to the amplif ier and connect the
negative power wire to it using appropriate
hardware (use of the JL Audio ECS master
ground lug, XB-MGLU is recommended).
Use the same size power wire as the wire

connected to the “+12 VD C” connection

(minimum 8 AWG), no longer than 36 inches

(90 cm) from the amplifier to the ground
connection point. In some vehicles, it may be
necessary to upgrade the battery ground wire.
(See page 5 for important notice).

7) Securely mount the amplifier.

8) Connect the positive and negative power

wires to the amplifier. A fuse near the
amplifier is not necessary.

9) Connect the remote turn-on wire

to the amplifier.

10) Connect the input cables to the amplifier.

11) Connect the speaker cables to the amplifier.

12) Carefully review the amplifier’s control

settings to make sure that they are set
according to the needs of the system.

13) Install the power wire fuse (50A for a

single G4500) and reconnect the negative
battery post terminal.

14) Turn on the source unit at a low level

to double-check that the amplifier is
configured correctly. Resist the temptation
to crank it up until you have verified the
control settings.

15) Make necessary adjustments to the input

sensitivity controls to obtain the right
overall output and the desired balance
in the system. See Appendix A (page 14)
for the recommended input sensitivity
setting method.

16) Enjoy the fruits of your labor with your

favorite music.

POWER CONNECTIONS

Before installing the amplifier, disconnect the
negative (ground) wire from the vehicle’s battery.
This will prevent accidental damage to the system,
the vehicle and your body during installation.

The G4500’s “+12 VD C” and “Ground”

connections are designed to accept 4 AWG power
wire. 4 AWG is a minimum power wire size for

this amplifier.

If you are installing the G4500 with other
amplifiers and wish to use a single main power
wire, use 4 AWG or larger main power wire
(depending on the overall current demands of all
the amplifiers in the system). This 4 AWG or
larger power wire should terminate into a
distribution block mounted as close to the
amplifiers as possible and should connect to the
G4500 with 4 AWG power wire.

Note: Smaller AWG numbers mean bigger wire
and vice-versa (1/0 AWG is the largest, 2 AWG is
smaller, then 4 AWG, then 8 AWG, etc.).

To connect the power wires to the amplifier,
first back out the set screw on the top of the
terminal block, using the supplied 2.5 mm hex
wrench. Strip 1/2 inch (12 mm) of insulation from
the end of each wire and insert the bare wire into
the terminal block, seating it firmly so that no
bare wire is exposed. While holding the wire in
place, tighten the set screw firmly, taking care not
to strip the head of the screw and mak ing sure
that the wire (not the insulation) is firmly gripped
by the set screw.

The ground connection should be made using
the same gauge wire as the power connection
and should be kept as short as possible, while
accessing a solid piece of sheet metal in the
vehicle. The surface of the sheet metal should
be sanded at the contact point to create a clean,
metal-to-metal connection between the chassis
and the termination of the ground wire. For
optimal grounding, we recommend the use of a
JL Audio ECS master ground lug (XB-MGLU).
Alternatively, a sheet metal screw or bolt can be
used with a star washer.

Any wires run through metal barriers (such
as firewalls), must be protected with a high
quality rubber grommet to prevent damage to the
insulation of the wire. Failure to do so may result
in a dangerous short circuit.

Many vehicles employ small (10 AWG -
6 AWG) wire to ground the battery to the
vehicle chassis and to connect the alternator’s
positive connection to the battery. To prevent
voltage drops, these wires should be upgraded
to 4 AWG when installing amplifier systems
with main fuse ratings above 60A.

FUSE REQUIREMENTS

It is absolutely vital that the main power wire(s)
to the amplifier(s) in the system be fused within
18 inches (45 cm) of the positive batter y post
connection. The fuse value at each power wire
should be high enough for all of the equipment
being run from that power wire. If only the
G4500 is being run from that power wire, we
recommend a 50A fuse be used. AFS (mini blade
fuse), AGU (big glass fuse) or MaxiFuse™ (big
plastic-body fuse) ty pes are recommended.

No fuse is required or recommended directly
before the amplifier power connection. If one is
desired, we recommend the use of a 50A fuse.

TURNON LEAD

The G4500 uses a conventional +12V remote
turn-on lead, typically controlled by the source
unit’s remote turn-on output. The amplifier will
turn on when +12V is present at its “Remote”
input and turn off when +12V is switched off. If
a source unit does not have a dedicated remote
turn-on output, the amplifier’s turn-on lead can
be connected to +12V via a switch that derives
power from an ignition-switched circuit.

The G4500’s “Remote” turn-on connector is
designed to accept 18 AWG – 12 AWG wire. To
connect the remote turn-on wire to the amplifier,
first back out the set screw on the top of the
terminal block, using the supplied 2.5mm hex
wrench. Strip 1/2 inch (12mm) of wire and insert
the bare wire into the terminal block, seating it
firmly so that no bare wire is exposed. While
holding the wire in the terminal, tighten the set
screw firmly, taking care not to strip the head of
the screw and making sure that the wire (not the
insulation) is firmly gripped by the set screw.

4 JL AUDIO G4500 JL AUDIO G4500 5

INPUT SECTION

The G4500’s input section allows you to send
signals to the amplifier section through the use of
either two or four differential-balanced inputs.

Input connections are via traditional
RCA-t ype jack s.

If you wish to send four discrete channels into
the G4500, simply use all four inputs (channels

1 & 2 and channels 3 & 4) and set the “CH 3&4
Input From” switch to “Discrete”.

If you wish to feed all four channels by using

only two channels of input, set the “CH 3&4
Input From” switch to “1&2 ” and use only the

inputs to channels 1 & 2.

Input Voltage Range:

A wide range of signal input voltages can be
accommodated by the G4500’s input sections
(200mV – 8V). This wide range is split up into
two sub-ranges, accessible via a switch located to
the left of the Input Connectors. Be aware that the
position of this switch will dictate the sensitivity
range for all four input channels.

The “Low” position on the “Input Voltage”

switch selects an input sensitivity range between

200mV and 2V. This means that the “Input
Sens.” rotary control will operate within that

voltage window. If you are using an aftermarket
source unit or an OEM interface processor with
conventional preamp-level outputs, this is most
likely the position that you will use.

The “High” position on the “Input Voltage”
switch selects an input sensitivity range between
800mV and 8V. This is useful for certain high­output preamp level signals as well as speaker­level output from source units and
small amplifiers.

To use speaker-level sources, splice the speaker
output wires of the source unit or small amplifier
onto a pair of RCA plugs for each input pair.
No line output converter is needed in most cases.

The output of the amplifier will decrease for
a given input voltage when the “Input Range”
switch is placed in the “High” position.
Conversely, the output will be higher with the
switch in the “Low” position. While this may
sound counter-intuitive, it is consistent with the
descriptions in this section.

INPUT SENSITIVITY CONTROLS

Once the appropriate “Input Voltage” range
has been selected, the controls labeled “Input
Sens.” located in each “Channel Controls”

section can be used to match the source unit’s
output voltage to the input stage of each pair of
amplifier channels for maximum clean output.
Rotating the control clockwise will result in
higher sensitivity (louder for a given input
voltage). Rotating the control counter-clockwise
will result in lower sensitivity (quieter for a given
input voltage.)

To properly set the amplifier for maximum
clean output, please refer to Appendix A (page

14) in this manual. After using this procedure,

you can then adjust any or all “Input Sens.”

levels downward if this is required to achieve the
desired system balance.

Do not increase any “Input Sens.” setting for
any channel(s) of any amplifier in the system
beyond the maximum level established during
the procedure outlined in Appendix A (page

14). Doing so will result in audible distortion
and possible speaker damage.

FILTER CONTROLS

Most speakers are not designed to reproduce
the full range of frequencies audible by the
human ear. For this reason, most speaker
systems are comprised of multiple speakers, each
dedicated to reproducing a specific frequency
range. Filters are used to select which frequency
range is sent to each section of a speaker system.
The division of frequency ranges to different
speakers can be done with passive filters (coils
and/or capacitors between the amplifier outputs
and the speakers), which are acceptable and
commonly used for filtering between mid­range speakers and tweeters. Filtering between
subwoofer systems and satellite speaker systems
is best done with active filters, which cut off
frequency content at the input to the amplifier.
Active filters are more stable than passive filters
and do not introduce extraneous resistance,
which can degrade subwoofer performance.

The active filter built into each channel section
of the G4500 can be used to eliminate potentially
harmful and/or undesired frequencies from
making their way through the amplifier sections
to the speaker(s). This serves to improve tonal
balance and to avoid distortion and possible
speaker failure. Correct use of these filters can
substantially increase the longevity and fidelity
of your audio system.

1) “Filter Mode” Control: The G4500 employs a

12dB per octave filter for each pair of channels
(one filter for channels 1&2 and another filter
for channels 3&4). Each of these filters can
be conf igured independently into one of two
filter ty pes or defeated completely by way of the
three-position “Filter Mode” switches:
“O ff ”: Defeats the filter completely, allowing
the full range of frequencies present at the
inputs to feed the amplifier. This is useful
for systems utilizing outboard crossovers or
requiring full-range reproduction from one or
both of the G4500’s channel pairs.
“LP ” (L ow-Pa ss): Configures the filter to
attenuate frequencies above the selected filter
frequency at a rate of 12dB per octave. This is
useful for connection of subwoofer(s) to one
or both of the G4500’s channel pairs in a
bi-amplified system.
“HP” (High-Pass): Configures the filter to
attenuate frequencies below the selected filter
frequency at a rate of 12dB per octave. This is
useful for connection of component speakers to
one or both of the G4500’s channel pairs in a
bi-amplified system.

2) “Filter Freq. (Hz)” The filter frequency

markings surrounding this rotar y control
are for reference purposes and are generally
accurate to within 1/3 octave or better. If you
would like to select the filter cutoff frequency
with a higher level of precision, consult the
chart in Appendix B (page 15).

Tuning Hint: If you are using the G4500 to drive
a subwoofer system (“LP” mode), a component
satellite speaker system (“HP” mode) or both,
80 Hz is a good baseline “Filter Freq. (Hz)”
setting. After properly adjusting the “Input
Sens.”, as outlined in Appendix A (page 14), you
can f ine tune the “Filter Freq. (Hz)” control to
achieve the desired system frequency response.

6 JL AUDIO G4500 JL AUDIO G4500 7

BASS BOOST CONTROLS

1) “CH 3&4 Bass Boost”: Found in the “Channel
3 & 4 Controls” section, this switch allows the

user to activate a 6 dB boost centered at 48 Hz

for channels 3 & 4. When the “CH 3&4 Bass

Boost” is activated, the inputs to “CH 3 (Left)”

and “CH 4 (Right)” are summed to create a

mono signal. The “Filter Mode” switch in the

“Channel 3 & 4” section must be in the “LP”

position for the bass boost to be functional.

2) “ Remote Bass Port”: This port allows you to

connect an optional remote boost knob (sold
separately as JL Audio Model RBC-1) that can
be mounted in the front of the vehicle. With
the RBC-1 connected, the boost is no longer
limited to 0 or +6 dB, allowing a variable
range of 0 to +12 dB of boost to be selected.

PREOUTS

The G4500 incorporates a pass-through
preamp output section, so that additional
amplifiers can be easily added to the system. This
pass-through pre-amp output can be configured
two different ways using the switch labeled

“Pre-Outs Input From”.

1) “1&2”: The preamp output delivers the same

signal that is connected to the CH 1&2 Inputs.
This mode is useful for feeding a subwoofer
amplifier when the G4500 is being used to

2) “Sum”: When the G4500 is being used to drive

front and rear speaker systems, this preamp
output mode will deliver a summed front/rear
stereo signal to a subwoofer amplifier, while
permitting fading of the front and rear speaker
systems from the source unit. This method
prevents a loss of signal to the subwoofer
amplifier when the system is faded to the front
or the rear by the head unit.

Note: Any signal delay between the front and rear
channels can result in a cancellation of signals
within certain frequency ranges when using the
“Sum” position. If you experience a loss of bass
output in the “Sum” position, compared to the

“1&2 ” position, you are likely dealing with a

delayed signal in either the front or rear outputs
of the source unit. If the front to rear delay is
desirable for other reasons or if it cannot be
defeated at the source unit, we recommend that

you use the “1& 2” position.

Note: In either mode, the preamp output signal
is not affected by the “CH 3&4 Bass Boost”

processing selected for the amplifier or by any
crossover filter selected (if the input signal is full­range, the preamp output will be full-range).

Note: The signal level of the “Preamp Output” is
line-level (low voltage), regardless of the position

selected in the G4500’s “Input Voltage” switch.

An additional amplifier connected to these
preamp outputs should have its input voltage
switch set to the “Low” position.

SPEAKER OUTPUTS

The G4500’s speaker outputs are designed to

accept 16 AWG - 8 AWG wire.

Each pair of the G4500’s channels are
designed to deliver power into speaker loads equal
to or greater than 2 ohms per channel when using

a “stereo” configuration and speaker loads equal

to or greater than 4 ohms per bridged pair of
channels when using a “bridged” configuration.

Speaker loads below 2 ohms nominal per
channel are not recommended and may cause
the amplifier to initiate a protection mode
which reduces power output.

BRIDGING CONSIDERATIONS

Bridging is the practice of combining the
output of two amplifier channels to drive a single
load. When bridged, each channel produces
signals of equal magnitude, but opposite polarity.
The combined output of the two channels
provides twice the output voltage available from a
single channel. The G4500 has been designed for
bridging of its channel pairs without the need for
input inversion adaptors.

To bridge a pair of channels, use the

“Left +” and “Right –” speaker connectors only
(th e “ Left –” and “Right +” remai n unused).

When bridged, each channel will deliver
optimum power into a 4 ohm load.

When a pair of channels are bridged, they
will deliver 250W x 1 into a 4 ohm load or
160W x 1 into an 8 ohm load. Operating a
pair of bridged channels into a load lower
than 4 ohms is not recommended.

Because a bridged pair of channels requires that
both channels receive input, you need to
connect both left and right inputs to the source
unit. Connection of only one input will result in
reduced power output, increased distortion and
can cause the amplifier to overheat.
Do not do this!

When a pair of the G4500’s channels are
operating in bridged mode, the output will be in
mono (only one channel). This mono channel
can contain right channel only information,
left channel only information or the sum of
the information from both the right and left
channels. In order to achieve one of these options,
configure the inputs to that pair of channels in
one of these two ways:

1) Left Channel Only or Right Channel Only

Information: If you wish to send a left-only

or right-only signal to a pair of the G4500’s

channels, use a “Y-Adaptor” to split the single

channel signal into both left and right RCA
inputs. This option is useful when using a pair
of the G4500’s channels to drive left channel
speakers only and the other pair of the G4500’s
channels to drive right channel speakers only.

2) Left + Right Channel Information:

When bridged and fed by a stereo input, a pair
of the G4500’s channels will automatically
combine the left and right channels into a
summed mono (left + right) channel. This
option is useful when using a pair of the
G4500’s channels to drive a subwoofer system

or a summed mono center channel.
drive front and rear speaker systems. In this
mode, the preamp output signal will depend
only on the input signal level of CH 1&2,
allowing Channels 3&4 to be faded without
affecting the subwoofer level. If CH 1&2 is
faded in this mode, the signal level of the
preamp output will change accordingly.

8 JL AUDIO G4500 JL AUDIO G4500 9

AMPLIFIER STATUS INDICATOR LIGHTS &
PROTECTION CIRCUITRY

There are two status indicator lights on the

input / control end of the amplifier.

1) “Power” (G reen): lights to indicate that the

amplifier is turned on and operating normally.

2) “Protect” (Red): Indicates that the amplifier

protection circuitry has been activated to
prevent product failure due to a short-circuit
or a dangerously low impedance connected
to the amplifier output(s). Connecting the
speaker outputs to an impedance lower than
2 ohms stereo (4 ohms bridged) will cause
this protection mode to activate. When this
protection mode is activated, the amplifier will
reduce it maximum power output to protect its
circuitry, which will manifest itself as increased
distortion. When the problem is corrected, the
amplifier will return to normal operation.

Advanced Rollback Thermal protection

Unlike conventional thermal protection
systems, which shut down an amplifier when it
overheats, this system protects the amplifier by
gradually reducing power output if the amplifier’s
safe operating temperature is exceeded. The
amplifier will continue to operate and return
to normal power output once its temperature
returns to a normal range.

Low-Voltage protection:

If the car’s supply voltage drops below 10

volts, the entire amplifier will shut itself off to

protect its internal circuitry. The green “Power”

indicator will turn off when this occurs. The
amplifier will turn back on when voltage climbs
back above 10 volts. This may happen in a rapid
cycle when bass-heavy program material causes
a weak charging system to dip below 10 volts
momentarily. If this is happening in your system,
turn your audio system off and have your power
wiring, ground connections and charging
system inspected.

SERVICING YOUR JL AUDIO AMPLIFIER

If your amplifier fails or malfunctions, please
return it to your authorized JL Audio dealer so
that it may be sent in to JL Audio for service.
There are no user serviceable parts or fuses inside
the amplifier. The unique nature of the circuitry
in the JL Audio amplifiers requires specifically

trained service personnel. Do not attempt

to service the amplifier yourself or through
unauthorized repair facilities. This will not only
void the warranty, but may result in the creation
of more problems within the amplifier.

If you have any questions about the installation or

setup of the amplifier not covered in this manual,

please contact your dealer or technical support.

JL Audio Technical Support:

(9 5 4 ) 4 4 3 -11 0 0

9:00 AM – 5:30 PM (Eastern Time Zone)

Monday - Friday

SYSTEM CONFIGURATIONS

The G4500 is a f lexible amplifier, well-suited
for a multitude of system configurations. In
this section, the most likely configurations are
explained in detail.

Once you have selected your desired
configuration, you can use the amplifier panel
drawing on pages 18 & 19 to mark the required
switch positions for easy reference.

BIAMPLIFIED SYSTEMS

Bi-amplified systems are defined as systems
in which separate amplifier channels drive low­frequency (LF) and high-frequency (HF) speakers
and are separately filtered to send appropriate
frequency ranges to each speaker system.

The most common application of
bi-amplification in mobile audio is to drive a
subwoofer system from one or more amplifiers or
channels and component speakers from separate
amplifiers or channels.

The G4500 can be configured to drive a
bi-amplified system by itself or with a separate
subwoofer amplifier.

Bi-Amplified System with one G4500

In this configuration, channels 3&4 of the
G4500 will drive subwoofers (stereo or bridged)
with low-pass filtering. Channels 1&2 will
drive component speakers in stereo with
high-pass filtering.

Input connection options for a bi-amplified system
with one G4500 are as follows:

A) No User Adjustability:
R e q u i r e d : a basic source unit or processor

with one pair of stereo outputs.

Inp ut Connections: a single pair of stereo source

unit outputs connected to the “CH 1 (Lef t)”
and“CH 2 (R ight)” inputs of the G4500 (select
“1&2 ” on the “CH 3&4 Input From” switch.

R e s u l t : the relative level of the LF and HF

channels will be determined by the G4500’s

“Input Sens.” settings and will not be user

adjustable from the front of the vehicle.

B ) Fade Subwoofer Level vs. HF Level
R e q u i r e d : a source unit or processor with two

pairs of stereo outputs.

Inp ut Connections: the first stereo pair source

unit outputs is connected to the “CH 1 (Left)”
and “CH 2 (Right)” inputs of the G4500. The

second stereo pair of source unit outputs is

connected to the “CH 3 (Left)” and “CH 4
(Right)” inputs (select “Discrete” on the “CH
3&4 Input From” switch).

R e s u l t : in this mode, the user has the ability to

fade or control the level of the LF channels
relative to the HF channels via the source
unit’s fader control without exceeding the
maximum clean output level set by each

amplifier section’s “Input Sens.” controls.

C) Subwoofer Level Control Only:
R e q u i r e d : a source unit or processor with

one pair of stereo outputs and dedicated
subwoofer outputs.

Inp ut Connections: the main stereo pair of

source unit outputs is connected to the “CH
1 (Left)” and “CH 2 (Right)” inputs of the

G4500. The source unit’s dedicated subwoofer

output is connected to the “CH 3 (Left)” and
“CH 4 (Right)” inputs (select “Discrete” on
the “CH 3&4 Input From” switch).

R e s u l t : in this mode, the user has the ability to

control the absolute level of the LF channels
relative to the HF channels.

Set the “Input Sens.” in the “Channel 3 & 4
Controls” section with the source unit’s
subwoofer level control set at 3/4 of full output.
See Appendix A (page 14) for details.

Crossover Setup for Bi-Amplified System
with one G4500:

Once the input sections have been configured

appropriately, go to the “Channel 3 & 4
Controls”. Select “LP” (low-pass) on the “Filter
Mode” switch and an appropriate “Filter Freq.”

(80 Hz is a good starting point).

10 JL AUDIO G4500 JL AUDIO G4500 11

Next, turn your attention to the “Channel 1 &
2 Controls” and select “HP” (high-pass) on the
“Filter Mode” switch and an appropriate “Filter
Freq.” (again, 80 Hz is a good starting point).

After proper adjustment of the “Input Sens.”

controls for both channel pairs using the method
shown in Appendix A (page 14), you can fine
tune filter frequencies and attenuate either pair
of channels to achieve proper balance. For precise
filter frequency information refer to Appendix B
(page 15).

Bi-Amplified System with one G4500 in
four-channel mode and a separate
subwoofer amplifier

This configuration requires that the separate
subwoofer amplifier has a built-in low-pass filter.
All JL Audio amplifiers have this feature.
In this configuration, channels 1&2 of the G4500
will drive front component speakerswith high­pass filtering. Channels 3&4 will drive
rear component speakers in stereo, also with
high-pass filtering. The separate amplifier
will drive the subwoofer system with low-pass
filtering (80 Hz is a good starting point).

Input connection options for a bi-amplified
system with one G4500 and a separate subwoofer
amplifier are as follows:

A) No User Adjustability:
R e q u i r e d : a basic source unit or processor with

one pair of stereo outputs.

Inp ut Connections: a single pair of stereo source

unit outputs is connected to the “CH 1 (Left)”
and “CH 2 (Right)” inputs of the G4500 (select
“1&2 ” on the “CH 3&4 Input From” switch).

Connect the subwoofer amplifier inputs to
the preamp outputs of the G4500 (Select

“1&2 ” on the “Pre-Outs Input From” switch.

Alternatively, the G4500 can receive its input
from the subwoofer amplifier’s preamp output

set to “full-range” mode (if applicable).

R e s u l t : the relative level of the LF and front

and rear HF channels will be fixed by the

G4 50 0’s “Input Sens.” settings (as well as the

subwoofer amplifier’s settings) and will not be
user adjustable from the front of the vehicle.

B) Fade Subwoofer Level vs. HF Level:
R e q u i r e d : a source unit or processor with front

and rear pairs of stereo outputs.

Inp ut Connections: one stereo pair of source unit

outputs is connected to the “CH 1 (Left)” and
“CH 2 (Right)” inputs of the G4500 (select
“1&2 ” on the “CH 3&4 Input From” switch).

The second stereo pair of source unit outputs
is connected to the subwoofer amplifier
inputs.

R e s u l t : with this option, the user has the ability

to fade the level of the subwoofer amplifier’s
input relative to t he HF channels, but
cannot control front-to-rear fading of the
HF channels. The relative level of the front and
rear HF channels will be fixed by the G4500’s

“Input Sens.” settings and will not be user

adjustable from the front of the vehicle.

C) Subwoofer Level Control Only:
Req uired: a source unit or processor with left,

right and dedicated subwoofer outputs.

Inp ut Connections: The main stereo pair

of source unit outputs is connected to the
“CH 1 (Left)” and “CH 2 (Right)” inputs
of the G4500 (select “1& 2” on the “CH 3&4
Input From” switch). The source unit’s
dedicated subwoofer output is connected to
the subwoofer amplifier inputs.

R e s u l t : with this option, the user has the ability

to control the absolute level of the subwoofer
channel relative to the HF channels, but
cannot fade the front and rear HF channels
relative to each other.

Set the subwoofer amplifier’s “Input Sens.”
with the source unit’s subwoofer level control
set at 3/4 of full output.

D) Front to Rear HF Fading and Subwoofer
Level Control:
R e q u i r e d : a source unit or processor with

front and rear pairs of stereo outputs plus a
dedicated subwoofer output.

Inp ut Connections: one stereo pair of source unit

outputs is connected to the “CH 1 (Left)” and
“CH 2 (Right)” inputs of the G4500.
The second stereo pair of source unit
outputs is connected to the “CH 3 (Left)”
and “CH 4 (Right)” inputs of the G4500
(se lec t “Discrete” on the “CH 3&4 Input
From” switch). The source unit’s dedicated
subwoofer output is connected to the
subwoofer amplifier inputs.

R e s u l t : with this option, the user has the ability to

fade the front and rear HF channels relative to
each other and also has the ability to control
the absolute level of the subwoofer channel
relative to the HF channels.

Set the subwoofer amplifier’s “Input Sens.”
with the source unit’s subwoofer level control
set at 3/4 of full output.

Crossover Setup for Bi-Amplified System with
one G4500 and a separate subwoofer amplifier:

Once the input and preamp output sections

have been configured appropriately, go to the

“Channel 1 & 2 Controls” and “Channel 3 &
4 Controls” You will set both control sections

identically to start:

Select “HP” (high-pass) on the “Filter Mode”

switch and an appropriate “Filter Freq.” (80 Hz is
a good starting point). Make these adjustments to
both control sections.

After proper adjustment of the G4500’s

“Input Sens.” controls, and the subwoofer
amplifier’s input sensitivity controls, you can fine
tune filter frequencies and attenuate either pair
of channels to achieve proper balance. For proper
adjustment of the “Input Sens.” controls of the
G4500 use the method shown in Appendix A
(page 14). For precise filter frequency information
for the G4500 refer to Appendix B (page 15).
Refer to the subwoofer owner’s manual for
proper adjustments.

12 JL AUDIO G4500 JL AUDIO G4500 13

APPENDIX A:
Input Sensitivity Level Setting

Following the directions below will allow the
installer to adjust the input sensitivity of each
amplifier channel pair simply and easily in just a
few minutes using equipment which is commonly
available in installation bays.

Necessary Equipment

• Digital AC Voltmeter

• CD with a sine-wave test tone recorded at

0 dB reference level in the frequency range
to be amplified for that set of channels
(50 Hz for subwoofer channels, 1 kHz for a

midrange application). Do not use attenuated

test tones (-10 dB, -20 dB, etc.).

The Nine-Step Procedure

1) Disconnect the speaker(s) from the

amplifier’s speaker output connectors.

2) Turn off all processing (bass/treble, loudness,

EQ, etc.) on the source unit, processors (if
used) and amplifier. Set fader control to center
position and subwoofer level control to 3/4 of
maximum (if used to feed the G4500).

3) Switch the “Input Voltage” switch to “Low”

and turn the “Input Sens.” control all the
way down.

4) Set the source unit volume to 3/4 of full

volume. This will allow for reasonable gain
overlap with moderate clipping at full volume.

5) Using the chart on this page, determine the target

voltage for input sensitivity adjustment according
to the nominal impedance of the speaker system
connected to t he amplifier outputs.

6) Verify that you have disconnected the speakers

before proceeding. Play a track with an

appropriate sine wave (within the frequency
range to be amplified by the G4500) at 3/4
source unit volume.

7) Connect the AC voltmeter to the speaker output

connectors of the amplifier. If the channel
pair is operating in stereo, it is only necessary
to measure one channel. If bridged, make sure
you test the voltage at the correct connectors
(L+ and R–).

8) Increase the “Input Sens.” control until the

target voltage is observed with the voltmeter.

9) Once you have adjusted the G4500 to its

maximum low-distortion output level,
reconnect the speaker(s). The “Input Sens.”
controls can now be adjusted downward if the
amplifier requires attenuation to achieve the
desired system balance.

Do not increase any “Input Sens.” setting for
any amplifier channel or channel pair in the
system beyond the maximum level established
during this procedure. Doing so will result in
audible distortion and possible speaker damage.

It will be necessary to re-adjust the

“Input Sens.” for the affected channels if any
equalizer boost is activated after setting the
“Input Sens.” with this procedure. This applies
to any EQ boost circuit, including source unit
tone controls or EQ circuits. EQ cuts will not
require re-adjustment.

Nom.

Impedance

8

6

4

3

2

Target AC Voltage

Stereo Bridged

17.8 V 26.8 V

17.8 V 25.6 V

17.8 V 24.6 V

17.3 V not recommended

15.8 V not recommended

APPENDIX B:
Precise Frequency Selection Chart

“FILTER FREQ” AMP FILTER

Detent Panel Actual
Number Marking Freq.

Full counter-clockwise: 53

01 ............................53

02 ...........“50” ............53

03 ............................53

04 ............................54

05 ............................54

06 ............................55

07 ............................55

08 ...........“55” ............56

09 ............................56

10 ............................57

11 ............................58

12 ............................59

13 ............................62

14 ...........“60” ............65

15 ............................65

16 ............................66

17 ............................70

18 ............................73

19 ............................77

20 ...........“80” ............81

21 ............................84

22 ............................88

23 ............................94

24 ...........................101

25 ...........................104

26 .......... “120” ..........115

27 ...........................118

28 ...........................128

29 ...........................137

30 ...........................146

31 ...........................164

32 .......... “150” ..........177

33 ...........................193

34 ...........................197

35 ...........................209

36 ...........................213

37 ...........................216

38 .......... “200” ..........218

39 ...........................225

Full-clockwise: 225

APPENDIX C:
G4500 Specifications

General Specifications:

Recommended Fuse Value: 50A

Recommended Fuse Type: AFS, AGU or MaxiFuse™

Input Sections:

No. of Inputs: Two Stereo Pairs

In put Ty pe: Differential-balanced with RCA jack inputs

Input Range: Switchable from 200mV - 2V RMS to

800mV - 8V RMS

Amplifier Section:

Amplifier Topology: Class A/B with patented Absolute

Symmetry™ dual N-Channel MOSFET output design

Power Supply: Unregulated MOSFET switching type

Rated Power at 14.4V with less than

1% THD+Noise (20Hz - 20 kHz)

Stereo, all channels driven:

80W RMS x 4 @ 4 ohms, 125W RMS x 4 @ 2 ohms

Bridged, all channels driven:

160W RMS x 2 @ 8 ohms, 250W RMS x 2 @ 4 ohms

Rated Power @ 12.5V with less than

1% THD + Noise (20Hz - 20 kHz)

Stereo, all channels driven:

60W RMS x 4 @ 4 ohms, 90W RMS x 4 @ 2 ohms

Rated Power Bridged, all channels driven:

120W RMS x 2 @ 8 ohms, 180W RMS x 2 @ 4 ohms

Signal to Noise Ratio: >104 dB referred to rated power

(A-weighted, 20 Hz-20 kHz noise bandwidth)

Frequency Response: 10 Hz - 25 kHz (+0, -1dB)

Damping Factor: >200 @ 4 ohms per ch./50 Hz,

>100 @ 2 ohms per ch. /50 Hz

Slew Rate: ± 22V/µs

Amplifier Filter:

Filter Type: State-variable, 12dB/octave Butterworth

with continuously variable cutoff frequency selection

from 50-200 Hz.

Configurable as Low- Pass or High-Pass. Defeatable.

Preamp Output:

Pass-through type, buffered.

Switch-selectable to pass signal from CH 1&2 inputs

only or from all four inputs (summed).

Dimensions(LxWxH):

13.8" x 9.25" x 2.50" (350mm x 235mm x 63.5mm)

Due to ongoing product development, all specifications are subject to
change without notice.

14 JL AUDIO G4500 JL AUDIO G4500 15

APPENDIX D: TROUBLESHOOTING
“How do I properly set the input sensitivity on my amplifier”

Please refer to Appendix A (page 14) to set the input sensitivity for

maximum, low-distortion output.

“My amplifier doesn’t turn on”

Check the fuse, not just visually, but with a continuity meter. It is

possible for a fuse to have poor internal connections that
cannot be found by visual inspection. It is best to take the
fuse out of the holder for testing. If no problem is found with
the fuse, inspect the fuse-holder.

Check the integrity of the connections made to each of the

“+12V DC ”, “Ground”, and “Remote” terminals. Ensure
that no wire insulation is pinched by the terminal set screw
and that each connection is tight.

Check to make sure there is +12V at the “Remote” connection of the

amplifier. In some cases, the turn-on lead from the source unit
is insuff icient to turn on multiple devices a nd the use of a relay
is required. To test for this problem, jump the “+12V DC ” wire
to the “Remote” terminal to see if the amplifier turns on. If this
does not work, proceed to t he next step.

“I get a distorted / attenuated sound coming out of the speaker(s)”

Check the speaker wires for a possible short, either between the

positive and negative leads or between either speaker lead
and the vehicle’s chassis ground. If a short is present, you
will experience distorted and/or attenuated output. The
“Protect” light will illuminate in this situation. It may be
helpful to disconnect the speaker wires from the amplifier
and use a different set of wires connected to a test speaker.

Check the nominal load impedance to verify that each channel

of the amplifier is driving a load equal to or greater than
2 ohms in stereo mode (4 ohms bridged).

Check the input signal and input signal cables to make sure signal

is present at the “Amplifier Inputs” and the cables are not
pinched or loose. It may be helpful to try a different set of
cables and/or a different signal source to be sure.

“My amplifier ’s output fluc tuates when I tap on it or hit a bump”

Check the connections to the amplifier. Ma ke sure that the

insulation for all wires has been stripped back far enough to
allow a good contact area inside the terminal block.

Check the input connectors to ensure that they all are making good

contact with the input jacks on the amplifier.

“My amplifier shuts off once in a while, usually at higher volumes”

Check your voltage source and grounding point. The power supply

of the G4500 will operate with charging system voltages
down to 10V. Shutdown problems at higher volume levels
can occur when the charging system voltage drops below
10V. These dips can be of very short duration making them

extremely difficult to detect with a common DC voltmeter.

To ensure proper voltage, inspect all wiring and termination
points. It may also be necessary to upgrade the ground
wire connecting the battery to the vehicle’s chassis and the
power wire connecting the alternator to the battery. Many
vehicles employ small (10 AWG - 6 AWG) wire to ground the
battery to the vehicle’s chassis and to connect the alternator to
the battery. To prevent voltage drops, these wires should be
upgraded to 4 AWG when installing amplifier systems with
main fuse ratings above 60A. Grounding problems are the

leading cause of misdiagnosed amplifier “failures.”

“My amplifier turns on, but there is no output ”

Check the input signal using an AC voltmeter to measure the

voltage from the source unit while an appropriate test tone is
played through the source unit (disconnect the input cables
from the amplifier prior to this test). The frequency used
should be in the range that is to be amplified by the amplifier
(example: 50 Hz for a sub bass application or 1 kHz for a full
range / high-pass application). A steady, sufficient voltage
(between 0.2 and 8.0-volts) should be present at the output of
the signal cables.

Check the output of the amplifier. Using the procedure explained in

the previous check item (after plugging the input cables back
into the amplifier) test for output at the speaker outputs of
the amplifier. Unless you enjoy test tones at high levels, it is
a good idea to remove the speaker wires from the amplifier
while doing this. Turn the volume up approximately half
way. 5V or more should be measured at the speaker outputs.
This output level can vary greatly between amplifiers but it
should not be in the millivolt range with the source unit at
half volume. If you are reading sufficient voltage, check your
speaker connections as explained below.

Check to ensure that the speaker wires are making a good

connection with the metal inside the terminal block. The
speaker wire connectors are designed to accept up to 8 AWG
wire. Make sure to strip the wire to allow for a sufficient
connection with the metal inside the terminal block.

16 JL AUDIO G4500 JL AUDIO G4500 17

INSTALLATION NOTES:

Use this diagram to document your amplifier’s switch and control positions.

18 JL AUDIO G4500 JL AUDIO G4500 19

LIMITED WARRANTY  AMPLIFIERS USA

JL AUDIO warrants this product to be free of defects in materials and workmanship for a
period of two (2) years.

This warranty is not transferrable and applies only to the original purchaser from an authorized

JL AUDIO dealer. Should service be necessary under this warranty for any reason due to manufacturing
defect or malfunction, JL AUDIO will (at its discretion), repair or replace the defective product with new
or remanufactured product at no charge. Damage caused by the following is not covered under warranty:

accident, misuse, abuse, product modification or neglect, failure to follow installation instructions,
unauthorized repair attempts, misrepresentations by the seller. This warranty does not cover incidental
or consequential damages and does not cover the cost of removing or reinstalling the unit(s). Cosmetic
damage due to accident or normal wear and tear is not covered under warranty.

Warranty is void if the product’s serial number has been removed or defaced.

Any applicable implied warranties are limited in duration to the period of the express warranty as
provided herein beginning with the date of the original purchase at retail, and no warranties, whether
express or implied, shall apply to this product thereafter. Some states do not allow limitations on implied
warranties, therefore these exclusions may not apply to you. This warranty gives you specific legal rights,
and you may also have other rights which vary from state to state.

If you need service on your JL AUDIO produc t:

All warranty returns should be sent to JL AUDIO ’s Amplifier Service Facility freight-prepaid through
an authorized JL AUDIO dealer and must be accompanied by proof of purchase (a copy of the original
sales receipt). Direct returns from consumers or non-authorized dealers will be refused unless specifically
authorized by JL AUDIO with a valid return authorization number.

Warranty expiration on products returned without proof of purchase will be determined from the
manufacturing date code. Coverage may be invalidated as this date is previous to purchase date. Non­defective items received will be returned freight-collect. Customer is responsible for shipping charges and

insurance in sending the product to JL AUDIO. Freight damage on returns is not covered under warranty.

For Service Information in the U.S.A. please call

JL Audio Customer Service: [phone]

9:00 AM – 5:30 PM (Eastern Time Zone)

JL Audio, Inc

10369 North Commerce Pkwy.

Miramar, FL 33025

(do not send product for repair to this address)

International Warranties:

Products purchased outside the United States of America are covered only

by that countr y’s distributor and not by JL Audio, Inc.

Absolute Symmetry™ Class A/B Amplifier Circuit is covered by U.S. Patent #6,294,959 and is pending in the
countries listed below. Austria, Belgium, Brazil, Canada, China, France, Germany, Indonesia, Italy, Japan, Republic of Korea,

Mexico, Ne therlands, Nor way, Russian Fe deration, Singapore, Sweden, Switzerlan d, United Kingdom , and all other PC T countries.

G4500MAN-CH-01-2008