Editing Audio crossover (section)

===Classification based on circuit topology===
[[File:Series parallel xover.GIF|thumb|340px|Series and parallel crossover topologies. The HPF and LPF sections for the series crossover are interchanged with respect to the parallel crossover since they appear in shunt with the low- and high-frequency drivers.]]

====Parallel====
Parallel crossovers are by far the most common. Electrically the filters are in parallel and thus the various filter sections do not interact. This makes two-way crossovers easier to design because, in terms of electrical impedance, the sections can be considered separate and because component tolerance variations will be isolated but like all crossovers, the final design relies on the output of the drivers to be complementary acoustically and this, in turn, requires careful matching in amplitude and phase of the underlying crossover. Parallel crossovers also have the advantage of allowing the speaker drivers to be [[Bi-wiring |bi-wired]], a feature whose benefits are hotly disputed.

====Series====
In this topology, the individual filters are connected in series, and a driver or driver combination is connected in parallel with each filter. To understand the signal path in this type of crossover, refer to the "Series Crossover" figure, and consider a high-frequency signal that, during a certain moment, has a positive voltage on the upper Input terminal compared to the lower Input terminal. The low-pass filter presents a high impedance to the signal, and the tweeter presents a low impedance; so the signal passes through the tweeter.  The signal continues to the connection point between the woofer and the high-pass filter. There, the HPF presents a low impedance to the signal, so the signal passes through the HPF, and appears at the lower Input terminal. A low-frequency signal with a similar instantaneous voltage characteristic first passes through the LPF, then the woofer, and appears at the lower Input terminal.

====Derived====
Derived crossovers include active crossovers in which one of the crossover responses is derived from the other through the use of a differential amplifier.<ref name="Chalupa1986" /><ref name="Elliot2017" /> For example, the difference between the input signal and the output of the high-pass section is a low-pass response. Thus, when a differential amplifier is used to extract this difference, its output constitutes the low-pass filter section.  The main advantage of derived filters is that they produce no phase difference between the high-pass and low-pass sections at any frequency.<ref name="Bohn" /> The disadvantages are either:
# that the high-pass and low-pass sections often have different levels of attenuation in their [[stopband]]s, i.e., their slopes are asymmetrical,<ref name="Bohn" /> or
# that the response of one or both sections peaks near the crossover frequency,<ref name="Elliot2017" /><ref name="Crawford1972" /> or both. 

In the case of (1), above, the usual situation is that the derived low-pass response attenuates at a much slower rate than the fixed response. This requires the speaker to which it is directed to continue to respond to signals deep into the stopband where its physical characteristics may not be ideal. In the case of (2), above, both speakers are required to operate at higher volume levels as the signal nears the crossover points. This uses more amplifier power and may drive the speaker cones into nonlinearity.