JL Audio RD400/4 Owner'S Manual Download Page 9

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Tuning Hint: If you are using the RD400/4

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
Sensitivity”, as outlined in Appendix A (page 14),
you can fine tune the “Filter Freq. (Hz)” control
to achieve the desired system frequency response.

PREOUTS

The RD400/4 incorporates a buffered, pass-

through preamp output section, so that additional
amplifiers can be easily added to the system. This
pass-through preamp output delivers a summed
stereo signal (CH. 1&3 / CH. 2&4) to a subwoofer
amplifier, while permitting fading of the front and
rear speaker systems from the source unit. This
method prevents a loss of signal to the subwoofer
amplifier when the system is faded to the front or
the rear by the head unit. Note: The level of the
preamp output is an average, taken from both left
and both right inputs. If only two inputs channels
are used, the preamp output level will be reduced
by –6 dB (or half).

Note: Any signal delay between the front and rear
channels can result in a cancellation of signals
within certain frequency ranges. If you experience
a loss of bass output, you are likely dealing with a
delayed signal in either the front or rear outputs
of the source unit. If the front to rear delay cannot
be defeated at the source unit, we recommend that
you use the FiX™ 82 or FiX™ 86 OEM Integration
DSP to correct any delayed signals. If the delay is
desirable for other reasons, we recommend using
Y-adaptors to split the input signal to feed other
amplifiers, rather than using the preouts.

Note: The preamp output delivers the same
signal that is connected to the RD400/4’s inputs.
The preamp output signal is not affected by the
amplifier’s filter controls. If the input signal is
full-range, the preamp output will be full-range.

Note: When the “Input Voltage” switch is in its

“Low” position, the level of the “Preouts” signals
matches the input signal levels (unity gain). When

the “Input Level” switch is in the “High”
position, the level of the input signal is attenuated
–12 dB to produce a line level signal at the

“Preouts”. This ensures a proper line level signal
output under both conditions.

If you plan to use the “Preouts” 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 RD400/4’s speaker outputs are designed

to accept 16 AWG - 8 AWG wire. To connect the
speaker wires to the amplifier, first back out the
set screws on 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.

Each pair of the RD400/4’s channels is

designed to deliver power into speaker loads
equal to or greater than 2 ohms per channel
when using a “stereo” configuration and speaker
loads equal to or greater than 4 ohms per bridged
pair when using a “bridged” configuration.

INPUT SEC

TION

(L)

(R)

Left

Mono

Right

Only

CH. 1&2

CH. 3&4

CH. 3

(L)