Editing Audio crossover (section)

====Active====
[[File:ThreeWayActiveCrossoverDiagram.png |thumb |right |450px |Implementation schematic of a three-way active crossover network for use with a stereo three-way loudspeaker system.]]

An active crossover contains active components in its filters, such as transistors and operational amplifiers.<ref name="AshleyKaminsky1971" /><ref name="Caldwell2013" /><ref name="Linkwitz1978" /> In recent years, the most commonly used active device is an [[operational amplifier]]. In contrast to passive crossovers, which operate after the power amplifier's output at high [[Electric current |current]] and in some cases high [[voltage]], active crossovers are operated at levels that are suited to power amplifier inputs. On the other hand, all circuits with [[gain (electronics)|gain]] introduce [[noise]], and such noise has a deleterious effect when introduced prior to the signal being amplified by the power amplifiers.

Active crossovers always require the use of power amplifiers for each output band. Thus a 2-way active crossover needs two amplifiers—one for the [[woofer]] and one for the [[tweeter]]. This means that a loudspeaker system that is based on active crossovers will often cost more than a passive-crossover-based system. Despite the cost and complication disadvantages, active crossovers provide the following advantages over passive ones:

[[File:Active Crossover.svg|thumb|right|300px|Typical usage of an active crossover, though a passive crossover can be positioned similarly before the amplifiers.]]

*a frequency response independent of the dynamic changes in a driver's electrical characteristics (e.g. from heating of the voice coil)
*typically, the possibility of an easy way to vary or fine-tune each frequency band to the specific drivers used. Examples would be crossover slope, filter type (e.g., [[Bessel filter |Bessel]], Butterworth, Linkwitz-Riley, etc.), relative levels, etc.
*better isolation of each driver from the signals being handled by other drivers, thus reducing [[intermodulation]] distortion and overdriving
*the power amplifiers are directly connected to the speaker drivers, thereby maximizing amplifier damping control of the speaker voice coil, reducing consequences of dynamic changes in driver electrical characteristics, all of which are likely to improve the transient response of the system
*reduction in power amplifier output requirement. With no energy being lost in passive components, amplifier requirements are reduced considerably (up to 1/2 in some cases), reducing costs, and potentially increasing quality.