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supplied with rack-mount ears but rack mount bolts
and nuts are not supplied. Ensure that, once mounted
in the rack, the amplifier is well ventilated and that its
ventilation apertures are not obstructed. If the system
is taken out of use for a long period, disconnect the
subwoofer amplifier from the mains supply.
Rack Mounting the SA250
The SA250 is supplied with two rack mounting
brackets for installation in standard equipment racks.
To install these brackets: Install the rack mount
bracket, inserting three of the small Philips head
machine screws through the bracket and the threaded
holes in the side of the amplifier. Repeat for the
bracket on the other side of the amplifier.
SA250 Rack Handles
The rack mount brackets are supplied with handles,
which can be installed or removed. The handles are
installed with two of the long Philips head machine
screws inserted through the rack mount bracket and
into the threaded holes in the handles. If you do not
use the handles, use the rubber hole plugs supplied
with the bracket hardware to fill the exposed holes.
Subwoofer Amplifier Connections
The SA250 subwoofer amplifier is fitted with a variety
of connection sockets on its rear panel:
1 x Mains input socket: Connect mains power using
the appropriate cable for your territory.
1 x Neutrik Speakon Output Socket: A four-pole
Speakon enabling connection of one or two (identical)
subwoofers. Speakon sockets provide a more secure
and reliable connection than bare-wire or 4mm
sockets.
4 x Binding Posts Outputs: Two pairs of binding
posts provide alternative bare-wire or 4mm socket
connection for one or two (identical) subwoofers.
1 x RCA Phono Input: Input socket for connection to
an AV processor or preamplifier subwoofer output.
1 x XLR Input: Alternative balanced input socket
for connection to an AV processor or preamplifier
subwoofer output.
1 x RCA Phono Output: Output socket for connection
to the input of a second subwoofer amplifier.
1 x XLR Output: Alternative balanced output socket
for connection to the input of a second subwoofer
amplifier.
2 x 3.5mm Jack Trigger Inputs: 12V trigger inputs to
enable automated control of amplifier standby and
movie/music function selection.
Connecting the subwoofer amplifier to the subwoofer,
including the use of Speakon plugs, is covered in the
Connecting Sections below.
Subwoofer Amplifier Controls
The SA250 subwoofer amplifier front panel carries the
following controls.
Volume: Sets the overall volume of the subwoofer.
Filter: Sets the low-pass cut-off frequency of the
subwoofer filter.
Low-pass In/Out: Engages or defeats the subwoofer
filter.
Phase: Reverses the subwoofer output phase.
Bass Extension: Provides three bass extension
options.
Movie/Music EQ: Provides equalisation options for
music or movie programme material.
On/Auto/Standby: Provides switch-on and standby
options.
Status Indicator: Illuminates to indicate the amplifier is
switched on.
Fault Indicator: Illuminates to indicate a fault condition.
Connecting the Subwoofer Amplifier
All connections should be made with the equipment
switched off.
The SA250 amplifier has two pairs of binding post
connection terminals and one four-pole Neutrik
Speakon connection socket on its rear panel. The
binding post terminals provide quick and easy
connection of stripped wires while Speakon sockets
provide a more secure and reliable connection method.
Two ISW-4 subwoofers can be connected to the
amplifier through use of either the two pairs of binding
posts or the supplied four-pole Speakon plug.
If the binding post terminals are to be used, connect
the positive cable or cables to the red terminals and
the negative cable or cables to the black terminals.
Incorrect connection can result in poor imaging and
loss of bass. Figure 9 illustrates the use of the binding
post terminals to connect one or two subwoofers.
If the Speakon option is to be used, disassemble
the Speakon plug as shown in Figure 10 connect
the positive cable to the terminal marked +1 and the
negative cable to the terminal marked -1. Terminals
+2 and -2 are to be used when two subwoofers
are connected. Incorrect connection can result in
poor imaging and loss of bass. Once the plug is
reassembled it can be inserted into the socket and
locked by twisting clockwise. Figure 11 illustrates
the use of the Speakon plug to connect one or two
subwoofers.
Keep the total impedance of the speaker cable
below the maximum recommended in the speaker
specification. Use a low inductance cable.
Connect the signal input to the subwoofer amplifier
using either the RCA phono or XLR options. A second
subwoofer amplifier can be daisy-chained from the first
by connecting to either the RCA phono or XLR output
sockets.
Subwoofer Amplifier Setup and Control
Before Auditioning
Before auditioning the subwoofer installation and fine-
tuning it, double check the connections. Make sure
in particular that the phasing is correct. The positive
terminals on the subwoofer (marked + and coloured
9
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