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8.2 Audio Input Connections - Powered Loudspeakers
8.2.1 Input Connection
The audio input connector will be a female XLR-3 or a type of terminal block
connector. Where both male and female XLR-3 connectors are provided, the input
connection can be made to either. Normally, the female connector is used for the
input signal, with the male connector functioning as a loop through connector for
routing the audio signal to additional loudspeakers.
Connect the output from your signal source (mixing
console, microphone, preamp, or other line-level
source) to the input connector on the rear panel. This
is an electronically balanced input designed to be
connected to a balanced signal source, but may be
connected to an unbalanced source. However, this
WILL create a ground loop, possibly causing
excessive noise. See Section 8.3.
Terminal Block Connections:
The proper terminal block connector connections are
labeled on the loudspeaker, normally as "+", "-", and
a shield (ground) symbol, as shown.
8.2.2 Loop or Thru Connector:
Use this connector to "daisy-chain" the input signal
to multiple loudspeakers. For terminal block
connections, use multiple wires to each terminal for
daisy-chaining.
If the signal processing, including the crossover, is
built in, full-range loudspeakers and subwoofers
may be daisy-chained together from a single signal
source.
8.3 Unbalanced Connections
Connection to an unbalanced signal source will create a ground loop that can result in
excessive noise (hum and buzz) in the system. The cause of ground loop noise can be difficult
to determine, as sometimes it can even be related to the internal design of some equipment.
For unbalanced-to-balanced connection, use an interconnect cable wired as shown above.
The important point is that the shield and the negative signal wire from the powered
loudspeaker input are connected at the unbalanced output and usually left "floating" at
the balanced input. This wiring scheme does not prevent a ground loop; it is simply the
best way to directly wire the interconnection. The usual way to eliminate ground loop
noise is by inserting an isolation transformer into the signal path.
A
B
1
2
3
Sheild
signal plus or cold
signal minus or hot
Connection
Pin
1
3
2
1
3
2
Typical XLR-3 Input and Loop Through Connectors
Typical Terminal Block Style Connector
and Shield Symbol
BALANCED
INPUT
POWERED
SPEAKER
UNBALANCED
OUTPUT
CABLE SHIELD
AC MAINS SAFETY GROUND
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