Description

This article is from the Car Audio FAQ, by Ian D. Bjorhovde (ianbjor@mobileaudio.com) with numerous contributions by others.

3.11 Should I get an active or a passive crossover? [JSC, JR]

Active crossovers are more efficient than passive crossovers. A
typical "insertion loss" (power loss due to use) of a passive crossover
is around 0.5dB. Active crossovers have much lower insertion losses,
if they have any loss at all, since the losses can effectively be
negated by adjusting the amplifier gain. Also, with some active
crossovers, you can continuously vary not only the crossover point, but
also the slope. Thus, if you wanted to, with some active crossovers
you could create a high pass filter at 112.3Hz at -18dB/octave, or
other such things.

However, active crossovers have their disadvantages as well. An active
crossover may very well cost more than an equivalent number of passive
crossovers. Also, since the active crossover has separate outputs for
each frequency band that you desire, you will need to have separate
amplifiers for each frequency range. Furthermore, since an active
crossover is by definition a powered device, the use of one will raise
a system's noise floor, while passive crossovers do not insert any
additional noise into a system.

Many people find it advantageous to use both active and passive
crossovers. Often, a separate amp is dedicated to the subwoofers, to
give them as much power as possible. The other amplifier is used to
power the mids and tweeters. In this scheme, an active crossover is
used to send only the sub-bass frequencies to the sub amp, and the
other frequencies to the other amp. The passive crossovers are used to
send the correct frequencies to the individual speakers (e.g., mids and
tweeters).

Thus, if you have extra money to spend on an active crossover and
separate amplifiers, and are willing to deal with the slightly more
complex installation and possible noise problems, an active crossover
is probably the way to go. However, if you are on a budget and can
find a passive crossover with the characteristics you desire, go with a
passive.

Continue to:

• prev: 3.10 What is a crossover? Why would I need one? [JSC]
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• next: 3.12 Should I buy an equalizer? [JSC]