JBL CS Series subwoofers are
available as a single 4-ohm voice
coil. Depending on the amplifiers
you are using, you may want to use
either one or several subwoofers
in the same enclosure to maximize
the power available from your
amplifiers. To achieve the maximum
amplifier output possible, you should
design a speaker system that
provides the lowest impedance
that your amplifier is rated to drive
safely. When designing a subwoofer
system, consider the following rules:
1. Don’t mix different subwoofer
or enclosure types in the same
system.
2. We recommend that you avoid
connecting separate woofers in
series. The amplifier-damping
factor (the amplifier’s ability to
control the motion of the woofer)
is expressed as a ratio of terminal
impedance (the sum of speaker
impedance, wire resistance
and the D.C. resistance of any
crossover coil connected to
the woofer) to amplifier-output
impedance. Therefore, connecting
separate woofers in series reduces
the damping factor of the amplifier
to a value of less than 1. This will
result in poor transient response.
3. Most amplifiers deliver exactly
the same amount of power
bridged into a 4-ohm load as they
do running a 2-ohm stereo load.
To design a subwoofer system
that maximizes available amplifier
power, keep the following rules
in mind:
1. The total system impedance
of woofers in parallel can be
calculated using the formula:
Impedance =
1
1
+
1
+
1 ...
w
1
w
2
w
3
where w is the nominal
impedance of the woofer.
2. The total system impedance
of woofers in series can be
calculated using the formula:
Impedance = w
1
+ w
2
+ w
3
...
The diagrams at right show parallel
and series speaker connections.
Figure 1. Parallel connection
Figure 2. Series connection
3
POWER CONNECTIONS
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