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INPUT SECTION
The M4500'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
If you wish to send four discrete channels into
the M4500, simply use all four inputs (channels
CH 3&4
Input From
Discrete
If you wish to feed all four channels by using
CH 3&4
Input From
1&2
inputs to channels 1 & 2.
Input Voltage Range:
A wide range of signal input voltages can be
accommodated by the M4500's input sections
(200mV – 8V). This wide range is split up into
two sub-ranges, accessible via a switch located to
position of this switch will dictate the sensitivity
range for all four input channels.
Low
Input Voltage
switch selects an input sensitivity range between
Input
Sens.
voltage window. If you are using a source unit
with conventional preamp-level outputs, this is
most likely the position that you will use.
High
Input Voltage
switch selects an input sensitivity range between
800mV and 8V. This is useful for certain high-
output preamp level signals as well as speaker-
level outputs from source units not equipped with
preamp-level outputs.
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To use speaker-level sources, splice the speaker
plugs for each input channel 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
Input Voltage
Input
Sens.
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,
Input Sens.
levels downward if this is required to achieve the
desired system balance.
JL AUDIO M4500
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 mid-
range 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 M4500 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
substantially increase the longevity and fidelity
of your audio system.
JL AUDIO M4500
1) "Filter Mode" Control: The M4500 employs a
(one filter for channels 1&2 and another filter
for channels 3&4). Each of these filters can
be configured independently into one of two
filter types or defeated completely by way of the
three-position Filter Mode switches:
"Off":
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 M4500's channel pairs.
"LP" (Low-Pass):
attenuate frequencies above the selected filter
useful for connection of subwoofer(s) to one
or both of the M4500's channel pairs in a
bi-amplified system.
"HP" (High-Pass):
attenuate frequencies below the selected filter
useful for connection of component speakers to
one or both of the M4500's channel pairs in a
bi-amplified system.
2) "Filter Freq. (Hz)" The filter frequency
markings surrounding this rotary 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
Tuning Hint: If you are using the M4500
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 fine tune the Filter Freq. (Hz) control to
achieve the desired system frequency response.
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