Specifications

3
8 COM
4
8
16
COM
10W
5W
2.5W
1.2W
70V
4.5V
8
88
Amplifier
70V
0
COM
SPKR
2W
1W
0.5W
COM
4
8
16
COM
10W
5W
2.5W
1.2W
COM
4
8
16
COM
10W
5W
2.5W
1.2W
A
B
C
CX Series Application Guide
With the helpful advice and input from contractors and consultants around the world, engineers at QSC designed
the CX Series amplifiers to be a versatile and reliable foundation for high quality installed sound systems.
This applications guide will help you design your sound system properly and utilize your CX amplifier(s) effectively.
It starts with a tutorial on distributed (constant voltage) speaker systems.
Distributed line principles
The best way to power a system of numerous relatively low-powered loudspeakers from a single amplifier is
to use a distributed line, which combines the simplicity of connecting speakers in parallel across a pair of wires
with the versatile capability to individually tailor the power delivered each speaker.
Distributed lines, often called constant-voltage lines, are catego-
rized by their maximum RMS voltage: 25-, 70-, 100-, 140-, 200-volt,
etc. The name “constant voltage” can be misleading because it
suggests that the voltage on the line does not correlate to the audio
signal level. But in fact, there’s nothing constant about the voltage
on a “constant-voltage” line; the voltage on the distributed line is
indeed an audio signal and will modulate as the audio itself does.
If you connect a voltmeter across a 70-volt line, you will seldom
actually measure 70 volts except on audio peaks. If the audio is
muted, you will measure zero volts.
Distributed-line amplifiers are designed to produce maximum power at the line voltage. For example, a 70-volt
amplifier will produce its maximum power at 70 volts, regardless of whether it’s a 50-watt, 150-watt, or 700-
watt model. What will differ from one power
rating to another is the amount of current the amp
can put out, as you can determine by using Ohm’s
Law. (If you need to brush up on Ohm’s Law, see
the sidebar on the next page.) Thus, a 70-watt
amp is designed to put out as much as 1 ampere
at 70 volts, while a 350-watt amp will be able to
produce up to 5 amperes at that voltage. Com-
pare that to regular low-impedance amplifiers,
whose power ratings are directly related to the
maximum voltages the amps can put into 8, 4, or
2 ohms, so that a higher-powered amp has a
higher output voltage for a given load than a
lower-powered amp does. For instance, an am-
plifier rated at 100 watts into 8 ohms can put out
Example of a loudspeaker connected to a
distributed line through a transformer
Example of a 70 volt
distributed line