Audio Crossovers allow you split the audio signal into high, medium and low frequencies allowing for optimal sound. This is true for home, car and commercial audio systems. Your sound is only as good as each component of your system.
The crossover also helps prevent potentially damaging low-frequency energy from reaching the midrange or tweeter drivers.
Visaton crossover networks are completely assembled units consisting of high quality components. They are mainly used in Visaton speaker kits but can be used with other projects as well. Please refer here for the listing of speaker kits which will give you more information and layouts / circuits of the crossovers.