Rockford Fosgate 250M manual Speaker Impedance, Using Passive Crossovers

INSTALLATION

10.Perform a final check of the completed system wiring to ensure that all connections are accurate. Check all power and ground connections for frayed wires and loose connections which could cause problems.

NOTE: Follow the diagrams for proper signal polarity.

!CAUTION: These amplifiers are not recommended for impedance loads below 2Ω.

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.

L

C

6dB/Octave Low-Pass

6dB/Octave High-Pass

Freq.

Speaker Impedance

Hertz

2 OHMS

4 OHMS

8 OHMS

L

C

L

C

L

C

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

L = Low-Pass (Inductor)

C = High-Pass (Capacitor)

For more information, see your Authorized Rockford

Fosgate Dealer.

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