Most types of loudspeakers use several transducers. The simplest speaker using multiple transducers is called “2-way speaker”. In this case, the speaker has two drivers, one woofer and one tweeter. There are hardly any drivers on the market that can reproduce the full audible frequency spectrum. Therefore manufacturers use multiple drivers.
A higher-end speaker uses 3 or even more drivers. A 3-way speaker uses one or two woofers along with a midrange speaker and a tweeter. Inside the speaker is a crossover. The crossover is a critical element which is responsible for splitting the audio signal into several components.
Let’s explain the function of the crossover in more detail. The signal that comes from an audio amplifier contains frequency components that cover the whole frequency spectrum which is typically the range between 20 Hz and 20 kHz. Each driver inside the speaker can only reproduce one part of this spectrum. The crossover is a filter that splits the frequency components of the audio signal into several subbands. Each subband signal is conneted to a specific driver inside the speaker which is capable of reproducing this specific frequency range. For example, the low-frequency subband components are connected to the woofer.
The crossover maximizes the power efficiency of the speaker and also protects the drivers.How To Split Frequencies In A Speaker by Robert Neill