JL Audio MHD900/5 User Guide

OWNER’S MANUAL

5-Channel Class-D Marine System Amplifier

Thank you for purchasing a JL Audio amplifier for

your marine sound system.

Your amplifier has been designed and manufactured to exacting

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

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.

2 | JL Audio - MHD900/5 Owner’s Manual

3

PROTECT YOUR HEARING!

Filter Frequ ency

Selector

(pg. 11)

Filter Frequ ency

Selector

(pg. 10)

Input Voltage

Selection

(pg. 9)

Infrasonic Filte r

Selector

(pg. 11)

Input Sensiti vity

Contro l
(pg. 10)

Input Mode

Selection

(pg. 9)

Filter Slope

Selection

(pg. 11)

Filter Frequ ency

Selector

(pg. 11)

Input Sensiti vity

Contro l
(pg. 10)

Filter Slope

Selection

(pg. 11)

Input Sensiti vity

Contro l
(pg. 10)

Power Sta tus

Indicator

(pg. 15)

Filter Slope

Selection

(pg. 11)

Left & Right
Input Jacks:

Subwoofer

(pg. 9)

Left & Right
Input Jacks:

Front Channels

(pg. 9)

Speaker Outputs

(pgs. 13-14)

Jack for
Remote Lev el
Control K nob

(pg. 13)

Left & Right
Input Jacks:

Rear Channels

(pg. 9)

Chassis Ground

Connector

(pgs. 6-7)

Remote Turn-On

Connector

(pgs. 6-7)

+12 V Power

Connector

(pgs. 6-7)

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 vessel.
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 vessel 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
vessels with 12 volt, negative-ground electrical
systems. Use of this product in vessels 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 vessel’s factory
installed electronic devices. You should also take
the time to securely mount the amplifier so that
it does not come loose in the event of a collision/
sudden jolt or as a result of the repeated vibrations
the vessel is prone to during normal operation.

Stupid Mistakes to Avoid:

• Check before drilling any holes in your vessel to

make sure that you will not be drilling through
the hull, a fuel tank, fuel line, wiring harness or
other vital vessel system.

• Do not run system wiring outside or underneath

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

• Protect all system wires from sharp edges

(metal, fiberglass, etc.) by carefully routing
them, tying them down and using grommets
and loom where appropriate.

• Do not mount the amplifier in the engine

compartment or in any other area that will
expose the amplifier circuitry to the elements.

While this amplifier is specially designed
for marine applications, it is not waterproof
and it should not be mounted where it is likely
to get wet.

4 | JL Audio - MHD900/5 Owner’s Manual

5

PRODUCT DESCRIPTION

The JL Audio MHD900/5 is a very powerful

and compact five-channel amplifier utilizing

patented Single Cycle Control ™ Class D

technology for all channels. This groundbreaking
technology delivers reference-grade, full­range sonic performance while requiring
far less current from the vessel’s electrical
system than a conventional amplifier.

JL Audio’s exclusive R.I.P.S. power supply

design optimizes the output of each channel

section for any impedance between 1.5 and 4

ohms per channel (3-8 ohms bridged on front
and rear sections) allowing you to get full use of
the MHD900/5’s performance capabilities with a
wide range of speaker systems.

The tightly regulated power supply design also
means that the MHD900/5’s clean power output
capability remains stable over a wide range of
vessel voltages, resulting in enhanced fidelity.

The MHD900/5 flexible, studio-grade signal
processing allows it to be deployed in several
different system configurations:

1) As a five-channel amplifier in a bi-amplified

system, driving four satellite speakers (100W x

4), plus a subwoofer system (500W x 1).

2) As a very powerful three-channel amplifier

in a bi-amplified system, driving t wo satellite
speakers (150W x 2, bridged), plus a subwoofer
system (500W x 1).

3) As a five-channel amplifier in a tri-amplified

system, driving two tweeters (100W x 2), plus
two woofer/mids (100W x 2), plus a subwoofer
system (500W x 1). An external 2-way
crossover is required for this application.

The MHD900/5’s flexible input and
crossover sections permit operation with
a wide variety of source units and system
configurations. It can be operated with a single
pair of stereo inputs, with two pairs of stereo
inputs (front and rear) or with separate inputs
for its front, rear and subwoofer channels.

As we said, it’s very flexible.

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 positive and negative power wire

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 vessel operation.

4 AWG is the minimum recommended
wire size for this amplifier. Use a 2 AWG
or 1/0 AWG main power wire with a power

distribution block when additional amplifiers
are being installed with the MHD900/5 and
powered from the same main power wire.

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 vessel.
Do not install the fuse until the power wire
has been connected to the amplifier.

4) Connect negative power wire to the negative

battery post. Use the same size power wire as
the wire connected to the “+12 V” connection.

5) Run signal cables (RCA cables) and remote

turn-on wire from the source unit or interface
processor to the amplifier mounting location.

6) Run speaker wire from the speaker systems to

the amplifier mounting location.

7) Securely mount the amplifier using

appropriate hardware. (See page 8 for detailed
mounting instructions).

8) Connect the remote turn-on wire and the

positive and negative power wires to the
amplifier’s power connector plug. Then insert
the power connector plug into the amplifier’s
power connector receptacle, pushing firmly.

9) Connect the RCA input cables

to the amplif ier.

10) Connect the speaker wires to the speaker

connector plugs and insert the plugs firmly
into the speaker connector receptacles.

11) Carefully review the amplifier’s control

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

12) Install power wire fuse (60A for a

single MHD900/5) and reconnect the negative
battery post terminal.

13) 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.

14) Make necessary adjustments to the input

sensitivity controls to obtain the right
overall output and the desired balance
in the system. See Appendix C (pages 18, 19)
for the recommended input sensitivity
setting method.

15) Enjoy the fruits of your labor with your

favorite music.

6 | JL Audio - MHD900/5 Owner’s Manual

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POWER AND TURNON CONNECTIONS

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

+12V Battery Connection

You will need to connect a power wire to
the vessel’s positive battery terminal, using an
appropriate power ring or specialized battery
terminal connector, such as the JL Audio
XB-BTU. This connection must be tight and
corrosion-free to ensure proper connectivity. This
wire MUST be fused appropriately for safety. Any
positive power wires run through metal barriers
, must be protected with a high quality insulating
grommet to prevent damage to the insulation
of the wire. Failure to do so may result in a
dangerous short circuit.

Power Wire Requirements

The MHD900/5’s “+12 V DC ” and “Ground”

connections are designed to accept 4 AWG
power wire. 4 AWG pure copper wire is

the minimum recommended wire size for
this amplifier. Use of smaller gauge wire
(including cheap wire that is fraudulently sold

as 4 AWG wire) can create a fire hazard.

If you are installing the MHD900/5 with other
amplifiers and wish to use a single main power

wire, use 2 AWG or 1/0 AWG pure copper wire
as a main power wire. This 2 AWG or 1/0 AWG

power wire should terminate into a distribution
block mounted as close to the amplifiers as
possible and should connect to the MHD900/5

with 4 AWG pure copper power wire, with

each smaller wire fused appropriately for each
amplifier or other electronics in the system.

Please note that lower 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.).

We do not recommend the use of “copper-clad
aluminum wire” or “CCA” wire because this
wire is significantly less conductive than pure
copper wire. Only use pure copper power wire,
such as JL Audio’s MetaWire™. Tinned copper
wire (silver color) is acceptable as the tin-plating
is only a very minor component of the wire.

Fuse Requirements

The installation of a fuse on the main power

wire, within 18 wire inches (45 cm) of the positive

battery terminal is vital to protect the wire and
the vessel from fire in the event of a collision
or short-circuit. The fuse value at each power
wire should be just high enough for all of the
equipment being run from that power wire. Do
not use a fuse with a value that far exceeds the
total fuse rating of the electronics connected to
the wire.

If only the MHD900/5 is being run from

a single power wire, install a 60A fuse to

protect the wire: AGU (big glass fuse). AFS
(small blade fuse) or MaxiFuse™ (big plastic-

body fuse) types are recommended.

If other amplifiers are also being powered from
a main power wire and exceed 80 amps in total
fuse rating, we recommend the use of an ANL
(large-blade) fuse and holder. Each amplifier can
then be fused independently at the outputs of
the power distribution block. Use JL Audio part

XC-FOA-2PAK and appropriate MaxiFuse™ type

fuses with JL Audio distribution blocks.

Please consult with your JL Audio
dealer to make sure that the wire, fuse
holder and fuse ratings are appropriate
for your system’s needs. The safety of
your installation depends on appropriate
power connections and fuse protection.

Ground Connection

The ground connection should be made using
the same gauge wire as the power connection.
It is common for the alternator to be grounded
through its chassis. If the alternator is not
grounded through its chassis and instead employs

a small (10 AWG - 6 AWG) wire to connect to
ground, this wire should also be upgraded to 4
AWG when installing amplifier systems with main

fuse ratings above 60A.

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

Turn-On Wire

The MHD900/5 uses a conventional +12V
remote turn-on wire, 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 ignition­switched circuit.

The MHD900/5’s “Remote” turn-on connector

is designed to accept 18 AWG – 12 AWG wire. 18
AWG is more than adequate for this purpose.

To connect the remote turn-on wire to the
amplifier, first back out the set screw on the

bottom of the Power Connector Plug, using the

supplied hex wrench. Strip 1/2 inch (12mm) of
wire and insert the bare wire into the receptacle,
seating it firmly so that no bare wire is exposed.
When using smaller wire, it may be necessary to
strip 1 inch of insulation from the wire and fold
the bare wire in half prior to insertion. While
holding the wire in the terminal, tighten the
set screw firmly using the supplied 2.5 mm hex
wrench, taking care not to strip the head of the
screw and making sure that the wire is firmly
gripped by the set screw.

Amplifier Power Connector Plug

To connect the power wires and the remote
turn-on wire to the amplifier, unplug the power
connector plug from the amplifier chassis (pull
back firmly) and back out the set screws on

the connector plug, using the supplied 4 mm

hex wrench for the +12 V DC ” and “Ground”
connections and the supplied 2.5 mm hex wrench
for the “Remote” connection. Strip 3/8 inch (10
mm) of insulation from the end of each wire and
insert the bare wire into the receptacle on power
connector plug, seating it firmly so that no bare
wire is exposed. While holding each wire in place,
tighten each set screw firmly, taking care not to
strip the head of the screw.

Never make power connections with a “live”
wire. Always disconnect the negative battery
post before making any connections or
adjustments to a 12V power connection!