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 each pair of amplifier channels
for maximum clean output, please refer to
Appendix B (page 20) in this manual. After using
this procedure, you can then adjust the relative
level of each channel pair by adjusting the input
sensitivity
downward
on either or both channel
pairs, if they require attenuation to achieve the
desired system balance.
Do not increase the “Input Sens.” setting for
any amplifier in the system beyond the maximum
level established during the procedure outlined in
Appendix B (page 20). Doing so will result in
audible distortion and possible speaker damage.
Be aware that both
“Input Sens.”
adjustments
will have to be made, regardless of how many input
cables are feeding the amplifier.These controls will
allow you to set the appropriate relative levels for
CH 1&2 relative to CH 3&4 and other amplifier
channels in the system.
CROSSOVER CONTROLS
Crossovers are groups of individual electronic filters
which allow only certain frequency ranges to pass
through them by attenuating frequencies outside
the selected range.These filters allow the user to
specify what frequency range will be sent out of
each channel section of the amplifier.This, in turn,
allows each speaker system to only reproduce a
range of frequencies it is well-suited for, resulting in
reduced distortion and improved fidelity.
CH 1&2 Filter Section:
1) “Filter Type” Control:
Located in the
“CH 1&2
Filter Section”
, this switch allows you to configure
the CH 1&2 filter into one of three filter types:
“LP” (Low-Pass):
Configures the CH 1&2 filter to
attenuate frequencies above the selected filter
frequency. Useful for connection of subwoofer(s) to
CH 1&2 in a bi-amplified system.
“BP” (Bandpass):
Configures the filter to attenuate
frequencies above the selected filter frequency
and
below the frequency selected in the CH 3&4 High-
Pass Filter. This creates a true bandpass filter well-
suited for driving mid-bass or mid-range speakers in
a tri-amplified system.
“HP” (High-Pass):
Configures the CH 1&2 filter to
attenuate frequencies below the selected filter
frequency. Useful for connection of component
speakers to CH 1&2 in a bi-amplified system.
2) “Filter Mode/Slope” Control:
This switch
allows you to defeat the CH 1&2 filter or select
from two filter slopes.
“Off”:
Defeats the filter for CH 1&2 completely,
allowing the full range of frequencies present at the
inputs to feed that pair of channels.This is useful for
systems utilizing outboard crossovers or requiring
full-range reproduction from that pair of channels.
“12dB”:
Configures the filter for CH 1&2 to
attenuate frequencies above or below the selected
filter frequency at a rate of 12 dB per octave
(Butterworth alignment).
JL AUDIO
450/4
7
TURN-ON LEAD
The 450/4 uses a conven12V remote
turn-on lead, 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
ignition-switched circuit.
The 450/4's
“Remote”
turn-on connector is
designed to accept 18 AWG – 8 AWG wire. 12
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 top of
the amplifier, using the supplied hex wrench. Strip
1/2 inch (12mm) of wire and insert the bare wire
into the receptacle on the front panel of the
amplifier, 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, taking care not to strip the head of
the screw and making sure that the wire is firmly
gripped by the set screw.
CH 1&2 / CH 3&4 INPUT SECTIONS
The 450/4 has two separate input sections, one
for CH 1&2 and another for CH 3&4. Each section
contains a pair of RCA-type input jacks, an
“Input
Voltage”
switch and an
“Input Sens.”
rotary control.
The
“CH 1&2 Input Section”
also contains an
“Input
Mode”
switch to allow operation of all four amplifier
channels with one or two pairs of input signals.
1) Input Mode Switch:
If you wish to operate all
four channels of the 450/4 with a single pair of
stereo inputs, select the
“2ch”
position on the
“Input Mode”
switch and connect a single pair of
input cables to the input jacks in the
“CH 1&2
Input Section”
. In this mode, the amplifier will
route the signals connected to the CH 1&2 inputs
to CH 3&4 as well.
If you wish to use separate inputs for CH 1&2
and CH 3&4 (to allow front-to-rear fading, for
example) and the source unit is equipped with front
and rear outputs, select
“4ch”
on the
“Input Mode”
switch located in the
“CH 1&2 Input Section”
. In
this mode, you must connect separate pairs of input
cables to each input section.
2) Input Voltage Range:
A wide range of signal
input voltages can be accommodated by each of
the 450/4's input sections (200mV – 8V).This wide
range is split up into two sub-ranges, accessible via
switches located in each input section of the
amplifier.
Be aware that each input section's “Input
Voltage” switch will have to be configured,
regardless of how many input cables are actually
feeding the amplifier.
The
“Low”
position on each
“Input Voltage”
switch selects an input sensitivity range between
200mV and 2V.This means that the
“Input Sens.”
rotary control will operate within that voltage
window. If you are using an aftermarket source unit,
with conventional preamp-level outputs, this is most
likely the position that you will use.
The
“High”
position on each
“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 output
from source units and small amplifiers.To use
speaker-level sources, splice the speaker output
wires of the source unit or small amplifier onto a
pair of RCA plugs for each input pair.
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 above.
3) Input Sensitivity Adjustment:
Located next to
the
“Input Voltage”
switch in each input section is a
rotary control labeled
“Input Sens.”
. Once the
appropriate
“Input Voltage”
range has been
selected, this control can be used to match the
source unit's output voltage to the input stage of
each pair of amplifier channels for maximum clean
I M P O RTA N T
!
6
JL AUDIO
450/4
