JL Audio A2150 - Manual (Page 4)

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 the A2150 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 speaker failure. Correct
use of these filters can substantially increase the
longevity and fidelity of your audio system.
1) “Filter Mode” Control: The A2150 employs a
12dB per octave filter which can be configured
into one of two filter types or defeated
completely by way of the three-position “Filter
Mode” switch:
“Off”: Defeats the filter completely, allowing
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 the
A2150’s channels.
“LP”
(Low-Pass): Configures the filter to
attenuate frequencies above the selected filter
frequency at a rate of 12dB per octave. This is
useful for connection of subwoofer(s) to the
A2150’s in a bi-amplified system.
“HP”
(High-Pass): Configures the filter to
attenuate frequencies below the selected filter
frequency at a rate of 12dB per octave. This is
useful for connection of component speakers to
the A2150’s channels 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
chart in Appendix B (page 13).
Tuning Hint: If you are using the A2150 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 12), you
can fine tune the “Filter Freq. (Hz)” control to
achieve the desired system frequency response.
JL AUDIO A2150 7
INPUT SECTION
The A2150’s input section allows you to send
signal to the amplifier section through the use
of two differential-balanced inputs, one for
the left channel and one for the right channel.
Connection is via RCA-type jacks.
Input Voltage Range:
A wide range of signal input voltages can be
accommodated by the A2150’s input section
(200mV – 8V). This wide range is split up into
two sub-ranges, accessible via a switch located to
the left of the Input Connectors.
The “Low” position on the “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 or an OEM interface processor with
conventional preamp-level outputs, this is most
likely the position that you will use.
The “High” position on the “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. 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 above.
INPUT SENSITIVITY CONTROL
Once the appropriate “Input Voltage” range
has been selected, the control labeled “Input
Sens.” located in the “Amplifier Controls”
section can be used to match the source unit’s
output voltage to the input stage of the amplifier
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
12) in this manual. After using this procedure,
you can then adjust any or all “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.
6 JL AUDIO A2150