Operating instructions

15
CHAPTER 3: AMPLIFICATION AND AUDIO
The low-frequency drivers in the 1100-LFC are powered by a
2-channel proprietary Meyer Sound amplifier with bridged
MOSFET output stages. The audio signal is processed with an
electronic crossover, correction filters for phase and fre-
quency responses, and driver protection circuitry. Each chan-
nel has peak and rms limiters that prevent driver over-
excursion and regulate voice coil temperatures.
The 1100-LFC rear panel includes Input and Loop output con-
nectors for audio, Limit and Active LEDs, and RMS controls
(see Chapter 5, “RMS Remote Monitoring System”).
AUDIO CONNECTORS
The 1100-LFC comes standard with XLR 5-pin connectors
for audio Input and audio Loop output.
Audio Input (XLR 5-Pin Female)
The audio Input is an XLR 5-pin female connector and
accepts balanced audio signals with an input impedance of
10 kOhm. The connector uses the following wiring:
■ Pin 1 — 220 kOhm to chassis and earth ground (ESD
clamped)
■ Pin 2 — Signal (+)
■ Pin 3 — Signal (–)
■ Pin 4 — RMS (polarity insensitive)
■ Pin 5 — RMS (polarity insensitive)
■ Case — Earth (AC) ground and chassis
Pins 2 and 3 carry the input as a differential signal. Pin 1 is
connected to earth through a 220 kOhm, 1000 pF, 15 V
clamped network. This circuitry provides virtual ground lift
for audio frequencies while allowing unwanted signals to
bleed to ground. Make use audio cables have all three pins
connected on both ends. Telescopic grounding is not rec-
ommended, and shorting an input connector pin to the case
may cause a ground loop, resulting in hum.
TIP: If unwanted noise or hiss is produced by
the loudspeaker, disconnect its input cable. If
the noise stops, there is most likely nothing wrong
with the loudspeaker. To locate the source of the
noise, check the audio cable, source audio, and AC
power.
Audio Loop Output (XLR 5-Pin Male)
The audio Loop output is an XLR 5-pin male connector. It
allows loudspeakers to be looped from a single audio
source. For applications that require multiple 1100-LFCs,
connect the Loop output of the first unit to the Input of the
second, and so forth.
NOTE: The order in which loudspeakers are
connected when looping audio signals is unim-
portant. The Loop connector is wired in parallel to the
Input connector and transmits the unbuffered source
signal even when the 1100-LFC is powered off.
1100-LFC Rear Panel
1100-LFC Audio Connectors, Input and Loop Output