Harman JBL SUB 550P, Service Manual, Page: 6 / 43

SUBWOOFER REAR-PANEL CONTROLS AND CONNECTIONS
Phase switch: This switch determines whether the subwoofer driver’s
piston-like action moves in and out in phase with the system’s other
speakers. If the subwoofer were to play out of phase with the other speak-
ers, the sound waves from the other speakers could partially cancel out
the sound waves from the subwoofer, reducing bass performance and
sonic impact. This phenomenon depends in part on the placement of all
the speakers relative to each other in the room.
Input Mode switch: When this switch is in the “Normal” setting, the input
signal from the Line In connectors is active. When this switch is in the
“LFE” setting, the input signal from the LFE In connector is active, and the
subwoofer’s internal crossover is bypassed.
Level control: Use this control to adjust the subwoofer’s volume. Turn the
knob clockwise to increase the volume; turn the knob counterclockwise to
decrease the volume.
Crossover control: This control determines the highest frequency
at which the subwoofer reproduces sounds. The higher you set the
Crossover control, the higher in frequency the subwoofer will operate and
the more its bass will “overlap” that of the system’s other speakers. This
adjustment helps achieve a smooth transition of bass frequencies between
the subwoofer and the other speakers for a variety of different rooms and
subwoofer locations.
NOTE: The Crossover control functions only when
the Input Mode switch is in the “Normal” position. When the switch is
in the “LFE” position the subwoofer’s built-in crossover and Crossover
control are bypassed.
On/Standby indicator: This LED indicates whether the subwoofer is in
the On or Standby state:
• When the LED glows green, the subwoofer is turned on.
• When the LED glows red, the subwoofer is in the Standby mode.
• When the LED is off, the subwoofer’s Power switch is set to “Off.”
Line In connectors: The signals from these connectors pass through
the subwoofer’s internal low-pass crossover. When you’re connecting the
subwoofer to the preamp or subwoofer outputs of a receiver/processor
that does not have its own low-pass crossover network, use both Line In
connectors.
IMPORTANT: You must also set the Input Mode switch in
the “Normal” position. If your receiver/processor has only one subwoofer
output, you can use either the L or R connector.
LFE In connector: The signal from this connector bypasses the subwoof-
er’s internal low-pass crossover. When you’re connecting the subwoofer
to the dedicated subwoofer output of a receiver/processor that has its own
low-pass crossover network, use the LFE In connector.
IMPORTANT: You
must also set the subwoofer’s Input Mode switch in the “LFE” position.
Power switch: Set this switch in the “On” position to put the subwoofer in
the Standby mode (the On/Standby LED lights red); set this switch in the
“Off” position to turn the subwoofer off.
Power Cord connector: After you have made and verified all subwoofer
connections described in this manual, plug the power cord into an ac-
tive, unswitched electrical outlet for proper operation of the subwoofer.
DO NOT plug this cord into the accessory outlet found on some audio
components.
Green: On
Red: Standby
Level Control
Crossover Control
On/Standby Indicator
Phase Switch
Input Mode Switch
LFE In Connector
Line In Connectors
Power Switch
Power Cord
Connector
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