How to Set Up Active Crossovers

by Kevin Krause
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Crossovers are an integral part of any high-end audio system. They filter the audio signal by frequency and direct it to the best amp and speaker in the system for maximum audio clarity. While passive crossovers are installed between the speaker and amp, and may lead to volume loss and be hard to adjust, active crossovers filter the line signal from the stereo, allowing for a better-quality sound and ease of adjustment. A typical application for a three-way active crossover is in a car audio system, but they can also be found in professional public announcement rigs and home theater systems.

Step 1

Mount the active crossover in a location between your stereo head unit and your system's amplifiers. If you do not plan to adjust it much after initial install, keeping the crossover behind the dash panels is a good option. If you wish to have easier access to the crossover's controls, install the unit near your amplifiers under a seat or in your trunk.

Step 2

Connect the audio signal from the stereo unit to the audio inputs of the active crossover. Connect the outputs for each crossover band to the appropriate amplifier, i.e. route the low signal to the subwoofer amps, the high signal to the tweeters, etc.

Step 3

Make all necessary electrical connections. The crossover runs on 12-volt DC power and will need a power connection to the car's battery. You also must run a ground line-to the car's chassis. You will also want to run a connection to an ignition switched electrical signal so that the crossover does not drain the battery when the car is off. Consult the literature included with your crossover for complete wiring instructions.

Step 4

Set the crossover's lowpass filter at 80 Hz. This will allow only frequencies below 80 Hz, such as bass and kick drum, to pass through. This filter setting is used for the output routed to your subwoofer amps.

Step 5

Set the highpass filter's crossover point at 3,000 Hz. This will let high-frequency sounds such as cymbals and acoustic harmonics pass to your tweeters.

Step 6

Set the bandpass filter for your system's midrange speakers and amplifiers to cut off frequencies below 80 Hz and above 3,000 Hz.

Step 7

Play music typical to what you would listen to through your system and adjust the crossover filters to taste to match your speakers and amplifiers. As you move the filter range of one filter, you will need to adjust the others to compensate. If you were to change your lowpass to 90 Hz, the bandpass will need to be changed to have a low cutoff point of 90 Hz rather than 80--though some overlap is OK and may even be beneficial depending on your system.

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