However, if you want to operate an "active" system, you need an amplifier in your aftermarket amplifier, which you can recognize by the frequency control on the side of your amplifier. Nowadays, all conventional amplifiers on the market have a built-in crossover. In an active sound system, each speaker (tweeter, woofer) has its own amplifier channel. This significantly increases the available power, the dynamic range (from the quietest to the loudest sound) and the control over the sound of the system across the entire audio spectrum. Almost all amplifiers have built-in high and low pass filters that can act as crossovers in a component system. The correct setting of the frequency ranges requires experience, and we will be happy to help you with this! In an exemplary active 2-way loudspeaker system with subwoofer in a car, the original audio signal could be crossed over as follows: The low frequencies (e.g. 80 Hz and below) go to the subwoofer. The woofers in the doors receive frequencies between 80 and 3,000 Hz. All frequencies above 3,000 Hz are handled by the tweeters. Bear in mind that the crossovers listed here are only an example and do not apply to every car or speaker system. The best crossover for one vehicle may not be the best for another. It all depends on the speakers used and the acoustic characteristics of the car.