JL Audio A1800 owner manual Bass Boost Controls, Precise Frequency Selection The filter, Pre-Outs

BASS BOOST CONTROLS

Tuning Hint: A trunk mounted sub whose output has to “fight” through a rear deck or a back seat 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

Protect

Bass Boost Controls

Bass Boost

Remote

Bass Port

The preamp output signal is not affected by the “Bass Boost” processing selected for the amplifier or by any crossover filter selected (if the input signal is full-range, the preamp output will be full-range).

The signal level of the “Preamp Output” is

line-level (low voltage), regardless of the position selected via the A1800’s “Input Voltage” switch. An additional amplifier connected to these preamp outputs should have its input voltage switch set to the “Low” position.

Speaker loads below 2 ohms nominal are not recommended and may cause the amplifier to initiate a protection mode which reduces power output.

You will notice that there are two “+” positive connections and two “–” negative connections. This is to facilitate multiple speaker wiring. The two positive and two negative connections are connected in parallel inside the amplifier. Connecting two speakers, each to one set of positive and negative terminals, will result in a

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 Amplifier Filter: The Low-

Pass filter can also be defeated completely,

by switching the “Mode/Slope” switch to

the “Off” position. This is useful if you are

using an external active crossover in the

system. Keep in mind that turning the internal

crossover off also defeats the “Bass Boost”

processing (see next section for details). With

the internal crossover turned off, the A1800’s

1)“Bass Boost”: This switch allows the user to activate a 6 dB boost centered at 48 Hz. The “Filter Mode” switch in the “Amplifier Controls” section must be in the “LP” position for the bass boost to be functional.

2)“Remote Bass Port”: This port allows you to connect an optional remote boost knob (sold separately, JL Audio Model RBC-1) that can be mounted in the front of the vehicle. With the RBC-1 connected, the boost is no longer limited to 0 or +6 dB, allowing a range of

0 - 12 dB of boost to be selected.

PRE-OUTS

The A1800 incorporates a pass-through preamp output section, so that additional amplifiers can be easily added to the system. The preamp output delivers the same signal that is connected to the A1800’s inputs.

If you plan to use the “Pre-Outs” to feed a stereo amplifier, you must connect a stereo signal to the input of the amplifier. A mono signal into the amplifier will result in a mono signal out of the preamp output.

SPEAKER OUTPUTS

The A1800’s speaker outputs are designed to accept 16 AWG - 8 AWG wire.

The A1800 is designed to deliver power into speaker loads equal to or greater than 2 ohms.

To connect the speaker wires to the amplifier, first back out the set screws own the top of the terminal block, using the supplied 2.5 mm hex wrench. Strip 1/2 inch (12 mm) of insulation from the end of each wire and insert the bare wire into the terminal block, seating it firmly so that no bare wire is exposed. While holding the wire in place, tighten the set screw firmly, taking care not to strip the head of the screw.

parallel speaker connection. If only connecting one pair of speaker wires, it is not necessary to use both sets of connections.

upper frequency response limit is 250 Hz, due

to its bass-specific Class D design.

CH 1 (Left)

CH 2 (Right)

Pre-Outs

Power

8 JL AUDIO A1800 JL AUDIO A1800 9