Extra Features; Active Vs. Passive Crossovers - Rockford Fosgate AF/4HD Installation Manual

EXTRA FEATURES

Cascading from output to input to create 24dB per Octave slope.
ACTIVE - VS - PASSIVE CROSSOVERS
All crossovers are frequency divider networks. Both active and passive crossovers
audio frequencies before they arrive at the speakers, and pass to each speaker only the desired
frequencies. An active crossover is an electronic "black box" (i.e. the AF/4HD) containing
circuitry for frequency separation, and requires an electrical power supply. Passive crossovers
go between the amplifier and the speaker, using bulky indicators and capacitors. Passive
crossover components for low frequencies are particularly large and heavy. By contrast, active
crossovers separate frequencies with the same high and low pass filter functions as passive
crossovers, but since they are made with integrated circuits, they are much smaller and lighter.
Passive crossovers are usually much cheaper to use, since an additional amplifier isn't needed.
However, there are a number of disadvantages to passive crossovers.
.
.
.
All these disadvantages are reduced or eliminated with the use of an active crossover/amplifier
system.
FREQUENCY CONTROL: The response of a passive crossover depends strongly on the
characteristics of the particular speaker.
CROSSOVER SLOPE: Single component passive crossovers (1 cap or 1 inductor) only
provide 6dB per octave rolloff. 12dB per octave passive crossover require more design
time and expense.
FREQUENCY CHANGING: Components for a wide variety of passive crossover frequen-
cies are difficult to stock and inconvenient to change.
11
separate the