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| JL Audio - RD1500/1 Owner’s Manual
LOW-PASS FILTER CONTROL
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 low-pass filter built into the
RD1500/1 is designed to attenuate frequencies
above its filter frequency, so that the system’s
subwoofers do not reproduce any audible
midrange content.
This serves to improve tonal balance and
to avoid distortion. Correct use of the filter
can substantially improve the fidelity of your
audio system.
LP Filter Operation: The RD 500/1 monoblock
employs a 12 dB per octave low-pass active filter
with fully variable frequency selection between
50 Hz and 500 Hz via the “LP Filter Freq. (Hz)”
control knob (80 Hz is a good starting point for
tuning most systems).
“BASS BOOST” CONTROL
The RD1500/1 monoblock includes a single
band, boost-only bass equalizer controlled
by a rotary knob marked “Bass Boost (dB)”.
This control has a boost range of 0 dB (full-
counterclockwise) to +12 dB (full-clockwise) and
is centered at 45 Hz.
REMOTE LEVEL CONTROL (OPTIONAL)
With the addition of the optional Remote
Level Control (RBC-1), you can control the
subwoofer volume from the front of the vehicle.
The RBC-1 connects to the jack labeled
“Remote Level Control (RBC-1)” on the
Connection Panel of the amplifier using a
standard telephone cable (supplied with the
RBC-1). If desired, multiple RD amplifiers can be
controlled from a single RBC-1 controller using
a single-line, four-wire phone line splitter and
multiple phone cables.
When connected to the amplifier, the RBC-1
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 RBC-1 was not connected at all. In other
words, it operates strictly as a level attenuator.
