Bass Boost Controls; Speaker Outputs - JL Audio M-Series M4300 Owner's Manual

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 near the head unit. 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 M4300 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 M4300 is being used to
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.
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2) "Sum": When the M4300 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 full-
range, 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 M4300's "Input Voltage" switch.
An additional amplifier connected to these
preamp outputs should have its input voltage
switch set to the "Low" position.
JL AUDIO M4300

SPEAKER OUTPUTS

The M4300's speaker outputs are designed to
accept 16 AWG - 8 AWG wire.
Each pair of the M4300'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 M4300 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
(the "Left –" and "Right +" remain unused).
When bridged, each channel will deliver
optimum power into a 4 ohm load.
JL AUDIO M4300
When a pair of channels are bridged, they
will deliver 150W x 1 into a 4 ohm load or
90W 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 M4300'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 M4300'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 M4300's channels to drive left channel
speakers only and the other pair of the M4300'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 M4300'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
M4300's channels to drive a subwoofer system
or a summed mono center channel.
If you plan to use the "Pre-Outs" to feed
a stereo amplifier, you must connect a
stereo signal to the input of the amplifier.
A mono signal into the amplifier will result
in a mono signal out of the preamp output.
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