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| JL Audio - MHD900/5 Owner’s Manual
13
remote leVel Control (oPtional)
With the addition of the optional Remote Level
Control (HD-RLC), you can control the level of
the Subwoofer Channel of the MHD900/5 from
the front of the vessel. The HD-RLC connects
to the jack labeled
“Remote Level Control”
on
the Connection Panel of the amplifier using
a standard telephone cable (supplied with the
HD-RLC).
If desired, multiple MHD amplifiers can be
controlled from a single HD-RLC controller
using a simple phone line “splitter”
and multiple phone cables.
When connected to the amplifier, the HD-RLC
operates as follows. At full counter-clockwise
rotation, the audio will mute completely. At full
clockwise rotation the level will be the same as if
the HD-RLC was not connected at all. In other
words, it operates strictly as a level attenuator.
When no HD-RLC is connected, the Level
Control circuit is defeated.
The RBC-1 Remote Bass Control used with
JL Audio Slash, Slash v2, e-Series, A-Series and
G-Series amplifiers is NOT compatible with the
HD/MHD Series amplifiers. If you attempt to
connect an RBC-1 to an HD amplifer, the
control will not work. You must use the
HD-RLC controller.
sPeaker outPuts
The MHD900/5 employs JL Audio’s exclusive
Regulated, Intelligent Power Supply (R.I.P.S.)
design. The operation of the R.I.P.S. system is
independent for each channel section. This
sophisticated power supply allows the amplifier to
produce its optimum power into higher
impedances as well as low impedances.
The R.I.P.S.-equipped MHD900/5 gives
you the freedom to use a variety of speaker
configurations that achieve final nominal
impedances between 1.5 – 4Ω per channel
in stereo while maintaining 75 - 100W x 4
of clean power output. When bridged, each
main channel pair will optimize output at
150-200 watts between 3 – 8Ω. The mono
subwoofer channel will deliver its full 500W
output into any impedance between 1.5-4Ω.
The operation of the R.I.P.S. circuitry is
entirely automatic and adjusts itself every time the
amplifier is turned on. There are no user controls
to configure. The system operates through
multiple stages of impedance optimization,
choosing the stage most appropriate to the actual
impedance of the speakers you connect to it.
If you connect a load higher than 4Ω nominal
per channel in stereo mode (or 8Ω in bridged
mode), power will drop by half with every
doubling of impedance above 4Ω stereo / 8Ω
mono. If you connect a load lower than 1.5Ω
nominal per channel in stereo mode (or 3Ω in
bridged mode, the amplifier protection
circuitry activates a “safe” mode which reduces
amplifier power to protect the circuitry from
failure (the LED status indicator on the control
panel will light up amber to indicate that this
has happened). See page 15 for details.
bi-amPliFied sYstems
Bi-amplified systems are defined as systems
in which separate amplifier channels drive low-
frequency (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 MHD900/5 can be easily configured to
drive a complete bi-amplified system consisting
of a subwoofer and four main speakers or a
subwoofer and two main speakers.
bi-amplified system with one mHd900/5
driving four main speakers plus subwoofer
(5-Channel mode)
In this configuration, the
“Front”
channels
of the MHD900/5 will drive front component
speakers (stereo 100W x 2 @ 4Ω) with high-
pass filtering. The
“Rear”
channels will drive
rear component speakers in stereo (100W x 2
@ 4Ω) with high-pass filtering. The subwoofer
channel will drive the subwoofer system
(500W x 1 @ 1.5-4Ω) with low-pass filtering.
Once the input sections have been configured
appropriately, go to the
“Front Channel
Controls”
Section. Select
“12dB”
or
“24dB”
on
the
“High-Pass Filter”
and an appropriate
“Filter
Freq.”
(80-90 Hz is a good starting point).
Next, turn your attention to the
“Rear
Channel Controls”
Section and select
“12dB”
or
“24dB”
“High-Pass Filter”
switch and an
appropriate
“Filter Freq.”
(again, 80-90 Hz is a
good starting point).
Finally, in the
“Subwoofer Channel
Controls”
Section, select
“12dB”
or
“24dB”
on the
“Low-Pass Filter”
Switch
and a
“Filter Freq.”
of 80-90 Hz.
After proper adjustment of the
MHD900/5’s
“Input Range”
and
“Input
Sens.”
controls
, you can fine tune filter
frequencies and slopes and attenuate each
channel section to achieve proper balance.
bi-amplified system with one mHd900/5
driving two main speakers plus subwoofer
(3-Channel mode)
In this configuration, the
“Front”
channels
of the MHD900/5 will be bridged to drive the
left front component speaker system (150W x
1 @ 4Ω) with high-pass filtering. The
“Rear”
channels will be bridged to drive the right front
component speaker system (150W x 1 @ 4Ω),
also with high-pass filtering. The
“Subwoofer”
channel will drive the subwoofer system
(500W x 1 @ 1.5-4Ω) with low-pass filtering.
For information on proper bridging
techniques refer to the section titled
“Bridging
Considerations”
in this manual (page 14).
Once the input sections have been configured
appropriately, go to the
“Front Channel
Controls”
Section. Select
“12dB”
or
“24dB”
on the
“High-Pass Filter”
and an appropriate
“Filter Freq.”
(80-90 Hz is a good starting point).
Next, turn your attention to the
“Rear
Channel Controls”
section and set it exactly the
same as you set the
“Front Channel Controls”
.
Finally, in the
“Subwoofer Channel
Controls”
section, select
“12dB”
or
“24dB”
on the
“Low-Pass Filter”
switch
and a
“Filter Freq.”
of 80-90 Hz.
After proper adjustment of the MHD900/5’s
“Input Range”
and
“Input Sens.”
controls
,
you can fine tune filter frequencies and
slopes and attenuate each channel section to
achieve proper balance. Keep in mind that
the left and right front speakers will have
independent
“Input Sens.”
controls in this
configuration, and these need to be carefully
matched for proper stereo performance.
