JL Audio XD 1000/1v2 Manuel D'utilisation page 5

INPUT SENSITIVITY CONTROLS
The control labeled "Input Sens." can be used
to match the source unit's output voltage to the
input stage of the XD1000/1v2 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
) in this manual. After using this procedure,
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you can then adjust the "Input Sens." levels
downward if this is required to achieve the
desired system balance.
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 12).
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
8 | JL Audio - XD1200/1v2 Owner's Manual
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
XD1000/1v2 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.
2) LP Filter Operation: The low-pass filter in the
XD1000/1v2 is fully variable between 50 Hz
and 500 Hz via the "Filter Freq." control knob
(80 Hz is a good starting point for tuning most
systems). The filter also features the ability to
select between a moderate "12dB" per octave
or a steep "24dB" per octave slope via the "LP
Filter Mode/Slope" switch.
Depending on the subwoofer system and
the vehicle, different slopes may be required
to produce a smooth transition to the mid-
bass speakers in the system. Experiment to
find the slope which best matches the acoustic
requirements of your system.
Tuning Hint: A trunk mounted sub whose
output has to "fight" through a rear deck or a
backseat often benefits from the 12 dB/octave
slope which lets more upper bass content pass
through. A sub that fires directly into the
listening environment is more likely to benefit
from a 24 dB/octave slope.
Note: The above hint is not "set-in-stone"...
You should always listen to the system carefully to
determine the best choice as vehicle acoustics and
other factors play a big role in choosing the most
appropriate filter slope.
3) Precise Frequency Selection: The filter
frequency markings on the front panel of
the amplifier are for reference purposes and
are generally accurate to within 1/3 octave
or better. If you would like to select the filter
frequency with a higher level of precision,
consult Appendix B (page 13) of this manual.
This chart gives you a more accurate frequency
for each of the forty detented positions of the
frequency selection control. This method can
be very useful if the amplifier is mounted in
a location where you can't see the front panel
markings easily.
4) Defeating the LP Filter: The Low-Pass filter
can also be defeated completely, by switching
the "LP Filter Mode/Slope" switch to the
"Off" position. This is useful if you are using
an external active crossover in the system.
With the internal crossover turned off, the
XD1000/1v2's upper frequency response limit is
500 Hz, due to its subwoofer-specific design.
INFRASONIC FILTER
The "Infrasonic Filter" is a 24 dB/octave high-
pass filter, with a fixed cutoff frequency of 30 Hz.
This filter is designed to conserve amplifier power
and protect subwoofer systems, without audibly
degrading the sub-bass output.
With ported enclosures, the use of the
"Infrasonic Filter" is highly recommended to
protect the speaker(s) from excessive excursion
below box tuning.
With sealed enclosures, the use of the filter
is less necessary, but can still help protect the
speaker system from excessive excursion.
The "Infrasonic Filter" can be completely
defeated by selecting the "Off" position on its
switch. This bypasses all signal from flowing
through the circuit.
REMOTE LEVEL CONTROL (OPTIONAL)
With the addition of the optional Remote
Level Control (HD-RLC), you can control the
subwoofer volume from the front of the vehicle
The HD-RLC connects to the jack labeled
"Remote Level Control" on the Connection
Panel of the amplifier using a standard telephone
cable (supplied with the HD-RLC). If desired,
multiple XD (and HD) amplifiers can be
controlled from a single HD-RLC controller
using a single-line, four-wire phone line splitter
and multiple phone cables.
When connected to the amplifier, the
HD-RLC 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 HD-RLC was not
connected at all. In other words, it operates
strictly as a level attenuator.
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