Crossovers are active or passive components that govern which frequencies pass to the various drivers in a speaker system. In a speaker cabinet, the woofer, tweeter and midrange all receive different ranges. Active crossovers however send signals from a certain frequency up or down from that point, depending on speaker size and bass capabilities. Wiring multiple speakers to these devices correctly ensures everything sounds as it should, while protecting the various drivers in the system.
When you look at an average speaker, you will typically notice two components, known as drivers. A two-way speaker will have a small tweeter and a larger woofer or midwoofer. These drivers cannot play the same frequencies, so a passive crossover distributes the right frequencies to the right drivers, using a series of capacitors, coils and resistors. For example, a woofer might play from 20 to 3,000 hertz, with the tweeter playing from 3,000 to 22,000 hertz. The crossover slope is the degree to which the upper midrange frequency and lower tweeter frequency roll off, creating a seamless blend between the two. This roll-off is necessary in preventing a harsh peak of the crossover frequency, which in the case of 3,000 hertz would be perceived by most listeners as a harsh sound.
Active Crossovers are electronic devices, receiving full-range signals from a preamplifier via RCA or digital cables. The crossover then distributes filtered frequencies to various speakers or speaker drivers in a system. For example, in a car audio system, you may want your subwoofer to play from 20 to 100 Hertz, with your other speakers playing from 100 to 20,000 hertz. By inserting the active crossover between the head unit and the individual amplifiers in the system, you can adjust which speakers receive what frequencies by changing jumpers or moving switches. Active crossovers are preferred by audiophiles, often removing the passive crossovers in a given speaker system and powering each driver independently with an active setup.
Passive Crossover Wiring
Assuming the crossover component values are appropriate for the drivers in the speaker system, wiring to each is pretty straightforward. On most passive crossover boards will be printing, denoting the input wiring from the terminal cup and the individual woofer and tweeter outputs. Input wires are usually labeled "IN+" and "IN-." Woofer and tweeter outputs are normally shown as "W+," "W-," "T+" and "T-," respectively. Strip 1/2 inch from the flying ends of all the input and output wires. Crimp on a set of female spade connectors that match the size of the terminal cup and driver input terminals. Slide the right wires onto the matching terminals, then screw each component to the speaker cabinet. Connect speaker wire from the amplifier to the input posts on the outside of the terminal cup to complete the wiring.
Plug a pair of RCA cables from the preamplifier into the "IN" terminals on the crossover. Each output has a high-pass or low-pass section per output. High-pass terminals operate from a certain frequency and up, commonly used for smaller speakers like mid-ranges and tweeters. By comparison, low-pass filters are normally for subwoofers. Bandpass outputs operate between a set of frequencies, commonly utilized for mid-bass speakers that operate between the subwoofer and midrange. Plug a set of RCA cables from each output to the appropriate amplifier in the system designated to drive the individual speakers. Plug the active crossover into an outlet to turn the unit on. Connect speaker wire as needed from each amplifier to the individual speakers of drivers in the setup. Adjust any knobs or sliders as needed to attenuate signal to one or more amplifiers, as governed by your subjective desires.
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