Multi-Amplifier Systems - JL Audio NexD M400 Owner's Manual

sYstem ConFigurations
The M400/4 is a flexible amplifier, well-suited
for a multitude of system configurations. In
this section, the most likely configurations for
a system with a single M400/4 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 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 marine audio is to drive a
subwoofer system from one or more amplifiers or
channels and component speakers from separate
amplifiers or channels.
The M400/4 can be configured to drive a
bi-amplified system by itself or with a separate
subwoofer amplifier.
bi-amplified system with one m400/4
In this configuration, channels 3&4 of the
M400/4 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 M400/4 are as follows:
A) No User Adjustability:
Req uired: 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 (Left)"
and"CH 2 (Right)" inputs of the M400/4 (select
"2 Ch." on the "Input Mode" switch).
Res ult: the relative level of the LF and HF
channels will be determined by the M400/4's
"Input Sens." settings and will not be user
adjustable from the helm.
B) Fade Subwoofer Level vs. HF Level
Req uired: a source unit or processor with two
pairs of stereo outputs.
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Inp ut Connections: the first stereo pair of source
unit outputs is connected to the "CH 1 (Left)"
and "CH 2 (Right)" inputs of the M400/4.
The second stereo pair of source unit outputs
is connected to the "CH 3 (Left)" and "CH 4
(Right)" inputs (select "4 Ch." on the "Input
Mode" switch).
Res ult: 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:
Req uired: 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 M400/4. The source unit's dedicated
subwoofer output is connected to the "CH
3 (Left)" and "CH 4 (Right)" inputs (select
"4 Ch." on the "Input Mode" switch).
Res ult: 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 M400/4:
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).
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).

multi-amPliFier sYstems

Using the "Preamp Outputs" of the
M400/4, it is easy to configure many
different multi-amplifier systems.
The most common type involves the
addition of a subwoofer amplifier, such
as the M600/1. Common configurations
of such a system are described below.
bi-amplified system with one m400/4 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
M400/4 will drive front component speakers in
stereo with high-pass 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).
Here are three possible configuration options:
A) Fade Subwoofer Level vs. HF Level:
Req uired: 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 M400/4 (select
"2 Ch." on the "Input Mode" switch). The
second stereo pair of source unit outputs is
connected to the subwoofer amplifier inputs.
Res ult: with this option, the user has the ability
to fade the level of the subwoofer amplifier's
input relative to the 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 M400/4's
"Input Sens." settings and will not be user
adjustable from the front of the vessel.
B) 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 M400/4 (select "2 Ch." on the "Input
Mode" switch). The source unit's dedicated
subwoofer output is connected to the
subwoofer amplifier inputs.
Res ult: 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.
C) Front to Rear HF Fading and Subwoofer
Level Control:
Req uired: 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 M400/4.
The second stereo pair of source unit outputs
is connected to the "CH 3 (Left)" and "CH
4 (Right)" inputs of the M400/4 (select "4
Ch." on the "Input Mode" switch). The
source unit's dedicated subwoofer output is
connected to the subwoofer amplifier inputs.
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