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How Do Subwoofers Work?


    • A subwoofer, also known as a loudspeaker, is capable of reproducing base and frequencies ranging from 10Hz to 150Hz. Developed in the 1960s as an add-on speaker to enhance and strengthen the bass response in audio equipment; subwoofers grew in popularity around the 1970s. As audio technologies evolved and changed, producers (especially during the 1980s) were able to add additional low frequency content to recordings. These changes were previously restricted during the era of the record and boom after the advent of the cassette recorder and compact disc.


    • Subwoofers are constructed by mounting an 8-to-21-inch diameter woofer in an enforced enclosure. Multiple woofers can be used, and the enclosure can be made of wood or plastic. The subwoofer enclosure includes such design technologies as the bass reflex (a port is included in the enclosure), infinite baffle, horn-loaded and bandpass. Each will vary in efficiency and size and bass power. Passive subwoofers differ slightly, powering the subwoofer driver and enclosure by an external amplifier. Active subwoofers house the amplifier internally.

    Amplification and Equalization

    • Most active subwoofers use an internal amplifier built into the cabinet. However, some rely on equalization to boost or reduce output at determined frequencies. These systems are constructed to monitor the subwoofer's in-room response using a calibrated microphone. The microphone reading allows the automatic equalizer to improve the low frequency performance of the subwoofer. For optimum sound, the amplification will create a complementary combination of subwoofer, subwoofer location and room response. Equalization is essentially a user-adjusted control that corrects performance issues.

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