JL Audio 505 - Manual (Page 12)

7) Connect the AC voltmeter to the “Speaker
Outputs” or “Subwoofer Output” connectors of
the channel set that you are adjusting. For the
stereo channels, it is only necessary to measure one
channel. If bridged, make sure you test the voltage at
the correct connectors (L+ and R–).
8) Increase the “Input Sens.” control until the
target voltage is delivered for that set of channels.
If excessive voltage is read on either set of channels
with the control at minimum (full counterclockwise),
switch the appropriate “Input Voltage” switch to
“High” and re-adjust.
9) Once you have adjusted each set of
channels to its maximum unclipped output level,
reconnect the speaker(s).The “Input Sens.”
controls can now be adjusted downward if any
channels require attenuation to achieve the
desired system balance.
Do not increase any “Input Sens.” setting in
the system beyond the maximum level established
during this procedure. Doing so will result in
audible distortion and possible speaker damage.
It will be necessary to re-adjust the “Input
Sens.” for the affected channels if any equalizer
boost is activated after setting the “Input Sens.”
with this procedure.This applies to any EQ boost
circuit, including the amplifier’s “Bass EQ” and
source unit tone controls or EQ circuits. EQ cuts
will not require re-adjustment.
I M P O RTA N T !
JL AUDIO 500/5 23
APPENDIX B:
Input Sensitivity Level Setting
JL Audio amplifiers utilizing the Regulated
Intelligent Power Supply (R.I.P.S.) allow delivery of
their rated power when connected to any load
impedance from 1.5 - 4 Ω per channel (3 - 8Ω
bridged) and when connected to a charging system
with any voltage from 11 - 14.5V. This design is
beneficial for many reasons. One of these reasons is
ease of setup. Because each JL Audio amplifier will
always deliver the same amount of power within its
operational range of impedances and supply
voltages, the maximum, unclipped output is very
predictable.This makes setting the gain structure via
the input sensitivity controls very simple. Following
the directions below will allow the user to adjust
the input sensitivity of the amplifier(s) simply and
easily in just a few minutes using equipment which is
commonly available in installation bays.
Necessary Equipment
• Digital AC Voltmeter
• CD with a sine-wave test tone recorded at 0 dB
reference level in the frequency range to be
amplified for that set of channels (50 Hz for
subwoofer channels, 1 kHz for a midrange
application). Do not use attenuated test tones
(-10 dB, -20 dB, etc.).
The Nine-Step Procedure
(follow this procedure for each set of channels)
1) Disconnect the speaker(s) from the
amplifier’s “Front”, “Rear” and “Subwoofer
Output” connectors.
2) Turn “Off ” all processing on the source unit
and amplifier (bass/treble, loudness, EQ, etc.).
3) In all three input sections, switch the “Input
Voltage” to “Low” and turn the “Input Sens.”
control all the way down (counterclockwise).
4) Set the source unit volume to 3/4 of full
volume. If either set of channels is being driven by a
source unit’s dedicated subwoofer output, also
adjust the source unit’s subwoofer level control to
3/4 of maximum output.This will allow for
reasonable gain overlap with moderate clipping at
full volume.
5) Using the chart below, determine the target
voltage for input sensitivity adjustment according to
the nominal impedance of the speaker system
connected to each set of outputs.
6) Verify that you have disconnected the
speakers before proceeding. Play a track with an
appropriate sine wave (within the frequency range
to be amplified by the set of channels being
adjusted) at 3/4 source unit volume.
22 JL AUDIO 500/5
FRONT CH. REAR CH. SUB CH.
Nom. Imp. Stereo Bridged Stereo Bridged Mono
8 Ω 20.0 V 40.0 V 10.0 V 20.0 V 31.6 V
6 Ω 20.0 V 34.6 V 10.0 V 17.4 V 31.6 V
4 Ω 20.0 V 28.4 V 10.0 V not recommended 31.6 V
3 Ω 17.3 V 24.6 V 8.7 V not recommended 27.4 V
2 Ω 14.2 V not recommended not recommended not recommended 22.4 V
1.5 Ω 12.3 V not recommended not recommended not recommended 19.4 V