Chapter 1: Crown Amplifi ers In-Depth
15
Amplifi er Application Guide
1.3.3 Determining Appropriate Speaker Wire Gauge
You should choose loudspeaker cables with suffi cient gauge (thickness)
for the length being used. The resistance introduced by inadequate loud-
speaker cables will reduce both the output power and the motion control of
the loudspeakers. The latter problem occurs because the damping factor
decreases as the cable resistance increases. This is very important because
the amplifi er’s excellent damping factor can easily be negated by insuffi cient
loudspeaker cables.
Use the nomograph in Figure 1.23 and the procedure that follows to fi nd the
recommended wire gauge (AWG or American Wire Gauge) for your system.
1. Note the load impedance of the loudspeakers connected to each channel
of the amplifi er. Mark this value on the “Load Impedance” (A) line of the
nomograph.
2. Select an acceptable damping factor and mark it on the “Damping Factor”
(B) line. Higher damping factors yield greater motion control over the
loudspeakers, and therefore lower distortion. A common damping factor for
commercial applications is between 50 and 100. Higher damping factors
may be desirable for live sound, but long cable lengths often limit the high-
est damping factor that can be achieved practically. In recording studios
and home hi-fi , a damping factor of 500 or more is very desirable.
3. Draw a line through the two points with a pencil, and continue until it inter-
sects the “Source Resistance” (C) line.
4. On the “2-Cond. Cable” (D) line, mark the required length of the cable run.
5. Draw a pencil line from the mark on the “Source Resistance” line through
the mark on the “2-Cond. Cable” line, and on to intersect the “Copper Wire”
(E) line.
6. The required wire gauge for the selected wire length and damping factor is
the value on the “Copper Wire” line. Note: Wire size increases as the AWG
gets smaller.
7. If the size of the cable exceeds what you want to use, (1) fi nd a way to use
shorter cables, (2) settle for a lower damping factor, or (3) use more than
one cable for each line. Options 1 and 2 will require the substitution of new
values for cable length or damping factor in the nomograph. For option
3, estimate the effective wire gauge by subtracting 3 from the apparent
wire gauge every time the number of conductors of equal
gauge is doubled. So, if #10 wire is too large, two #13
wires can be substituted, or four #16 wires can be used for
the same effect.
1.3.4 Loudspeaker Protection
Crown amplifi ers generate enormous power. If your loud-
speakers don’t have built-in protection from excessive
power, it’s a good idea to protect them. Loudspeakers are
subject to thermal damage from sustained overpowering
and mechanical damage from large transient voltages.
Special fuses can be used to protect your loudspeakers in
both cases.
Depending on the application, you may
want to use a
PIP
™ module to protect
your loudspeakers (for PIP-compatible
amps only). When properly confi gured, all
PIP modules with signal-driven compres-
sion can provide loudspeaker protection.
For more information on available PIP
modules with signal-driven compression,
contact your Crown dealer or check the
current selection of PIP modules at www.
PIPs for Speaker Protection
