Editing Audio crossover (section)

====Passive====
[[File:Passive Crossover.svg|thumb|right|300px|A passive crossover circuit is often mounted in a [[speaker enclosure]] to split up the amplified signal into a lower-frequency signal range and a higher-frequency signal range.]]

A '''passive crossover''' splits up an audio signal after it is amplified by a single [[power amplifier]], so that the amplified signal can be sent to two or more driver types, each of which cover different frequency ranges. These crossover are made entirely of passive components and circuitry; the term "passive" means that no additional power source is needed for the circuitry. A passive crossover just needs to be connected by wiring to the power amplifier signal. Passive crossovers are usually arranged in a [[Cauer topology]] to achieve a [[Butterworth filter]] effect. Passive filters use [[resistor]]s combined with reactive components such as [[capacitor]]s and [[inductor]]s. Very high-performance passive crossovers are likely to be more expensive than active crossovers since individual components capable of good performance at the high currents and voltages at which speaker systems are driven are hard to make. 

Inexpensive [[consumer electronics]] products, such as budget-priced [[Home theater in a box]] packages and low-cost [[boom box]]es, may use lower quality passive crossovers, often utilizing lower-order filter networks with fewer components. Expensive [[hi-fi]] speaker systems and receivers may use higher quality passive crossovers, to obtain improved sound quality and lower distortion. The same price/quality approach is often used with sound reinforcement system equipment and musical instrument amplifiers and speaker cabinets; a low-priced [[stage monitor]], [[PA speaker]] or bass amplifier speaker cabinet will typically use lower quality, lower priced passive crossovers, whereas high-priced, high-quality cabinets typically will use better quality crossovers. Passive crossovers may use capacitors made from [[polypropylene]], metalized [[polyester]] foil, paper and [[electrolytic]] capacitors technology. Inductors may have air cores, powdered metal cores, [[ferrite core]]s, or laminated [[silicon]] steel cores, and most are wound with enameled [[copper]] wire. 

Some passive networks include devices such as [[Fuse (electrical)|fuses]], PTC devices, bulbs or [[circuit breaker]]s to protect the loudspeaker drivers from accidental overpowering (e.g., from sudden surges or spikes). Modern passive crossovers increasingly incorporate equalization networks (e.g., [[Zobel network]]s) that compensate for the changes in impedance with frequency inherent in virtually all loudspeakers. The issue is complex, as part of the change in impedance is due to acoustic loading changes across a driver's passband.

Two disadvantages of passive networks are that they may be bulky and cause power loss. They are not only frequency specific, but also [[Electrical impedance |impedance]] specific (i.e. their response varies with the electrical load that they are connected to). This prevents their interchangeability with speaker systems of different impedances. Ideal crossover filters, including impedance compensation and equalization networks, can be very difficult to design, as the components interact in complex ways. Crossover design expert [[Siegfried Linkwitz]] said of them that "the only excuse for passive crossovers is their low cost. Their behavior changes with the signal level-dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal."<ref name="LinkwitzCrossovers" /> Alternatively, passive components can be utilized to construct filter circuits before the amplifier. This implementation is called a passive line-level crossover.