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10
INSTALLA
TION
USING PASSIVE CROSSOVERS
A passive crossover is a circuit that uses capacitors and/or coils and is placed on speaker leads
between the amplifier and speaker. The crossover delegates a specific range of frequencies to the
speaker for optimum driver performance. A crossover network can perform one of three functions:
High-Pass (capacitors), Low-Pass (inductors or coils) and Bandpass (combination of capacitor and
coil).
The most commonly used passive crossover networks are 6dB/octave systems. These are easy to
construct and require one component per filter. Placing this filter in series with the circuit will
reduce power to the speaker by 6dB/octave above or below the crossover point depending on
whether it is a high-pass or low-pass filter. More complex systems such as 12dB/octave or
18dB/octave can cause impedance problems if not professionally designed.
Passive crossovers are directly dependent upon the speaker's impedance and component value for
accuracy. When passive crossover components are used in multiple speaker systems, the crossover's
effect on the overall impedance should be taken into consideration along with the speaker's
impedance when determining amplifier loads.
CAUTION: These amplifiers are not recommended for impedance loads below 2Ω
stereo and 4Ω bridged (mono).
80 4.1mH 1000mF 8.2mH 500mF 16mH 250mF
100 3.1mH 800mF 6.2mH 400mF 12mH 200mF
130 2.4mH 600mF 4.7mH 300mF 10mH 150mF
200 1.6mH 400mF 3.3mH 200mF 6.8mH 100mF
260 1.2mH 300mF 2.4mH 150mF 4.7mH 75mF
400 .8mH 200mF 1.6mH 100mF 3.3mH 50mF
600 .5mH 136mF 1.0mH 68mF 2.0mH 33mF
800 .41mH 100mF .82mH 50mF 1.6mH 26mF
1000 .31mH 78mF .62mH 39mF 1.2mH 20mF
1200 .25mH 66mF .51mH 33mF 1.0mH 16mF
1800 .16mH 44mF .33mH 22mF .68mH 10mF
4000 .08mH 20mF .16mH 10mF .33mH 5mF
6000 51mH 14mF .10mH 6.8mF .20mH 3.3mF
9000 34mH 9.5mF 68mH 4.7mF .15mH 2.2mF
12000 25mH 6.6mF 51mH 3.3mF 100mH 1.6mF
Freq.
Hertz
Speaker Impedance
2 OHMS
8 OHMS
4 OHMS
L L
L
C C
C
6dB/Octave Low-Pass
6dB/Octave High-Pass
L
C
L = Low-Pass (Inductor)
C = High-Pass (Capacitor)
For more information, see your
Authorized Rockford Fosgate Dealer.
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