A component designed to alter the frequency balance of an audio signal; an electronic set of filters used to boost or attenuate certain frequencies. A built-in EQ lets you tailor the sound to your listening tastes and to your vehicle's acoustics. Receivers with built-in EQs will have one or more equalizer "bands" in addition to standard bass and treble controls. These equalizer "bands" usually have fixed center frequencies and bandwidths (although some may be adjustable). More sophisticated built-in EQs offer parametric equalization, which allows you to set the amount (in dB) by which a certain frequency band is boosted or cut, and determine the width and/or center frequency of this band. This gives you extremely precise control of the tonal balance in your vehicle.