Most speakers will have multiple drivers. A driver is sometimes called a transducer, which is a device that turns one type of energy into another – in this case, electrical energy to sound energy. In a loudspeaker, it is often the case that we might want multiple drivers – one to handle low-end, one to handle the mid-range, and one to handle the treble. This latter driver is often called a tweeter. To get the benefit of this arrangement, we need to split the signal into different frequency components. The circuit that does this is called a crossover.