AUDIO CROSSOVER

What is a crossover? People can hear sound frequencies from 20-20000Hz. There is no one speaker capable of producing all frequencies throughout this range. Therefore, multiple speakers must be used. Usually, it is damaging for a speaker to produce frequencies lower than what it was designed for. Also, if two speakers produce sound at the same frequencies, then the sound at those frequencies will be louder. For these reasons, some type of circuit is necessary to make sure that each speaker only produces a certain set of frequencies. That circuit is a crossover

Audio crossovers are a class of electronic filters designed specifically for use in audio applications, especially hi-fi. Individual loudspeaker drivers are incapable of covering the entire audio spectrum, from low frequencies to high frequencies, with acceptable volume and lack of distortion by themselves.

Therefore a combination of multiple loudspeakers or drivers, each catering to a different frequency band, is the design pattern for most hi-fi speaker systems. Crossovers serve the purpose of splitting the audio signal into separate frequency bands which can be handled by individual loudspeaker drivers optimized for those bands. An audio crossover may also be constructed mechanically and is commonly found in full-range speakers, portions of whose cones/dust caps/whizzer cones are decoupled at progressively higher frequencies.

 
Reference:
1.http://www.lenardaudio.com/education/06_x-over.html
2.http://en.wikipedia.org/wiki/Audio_crossover
3.http://en.wikipedia.org/wiki/Linkwitz-Riley_filter