Audio EqualizersAn audio equalizer is typically found in home and car stereo systems and is used to alter or control the frequency response characteristics of an audio system. An audio equalizer provides more accurate control of tone or frequency than simple bass and treble controls. There are many types of equalizers and the two most common are graphic and parametric.
Graphic EqualizersA graphic equalizer is the simplest type and consists of multiple sliders or controls for boosting or cutting bands or frequencies of sound. For example, a typical five-band graphic equalizer has sliders for five fixed frequencies: 30Hz (low bass), 100Hz (mid-bass), 1kHz (midrange), 10kHz (upper midrange) and 20kHz (treble or high-frequency). The equalizer can boost or cut each frequency within a range of +/- 6dB or perhaps +/- 12dB depending on the model, but each frequency is fixed. A ten-band equalizer has controls for ten fixed frequencies, allowing greater tone control.
Parametric EqualizersA more complex type is the parametric equalizer, which controls more parameters of the sound than a graphic equalizer. A parametric equalizer can control three aspects of each frequency: level (boost or cut), the center or primary frequency and the bandwidth or range of each frequency.
Like the graphic equalizer, each frequency can be increased or decreased by +/- 6dB or +/- 12dB. However, a parametric equalizer can also control the center frequency. For example, if the graphic equalizer has a fixed control at 20Hz, a parametric equalizer can be adjusted to control a center frequency of 15Hz, 25Hz or 30Hz, etc. Each model varies, but the center frequency can be varied to adjust a specific frequency.
A parametric equalizer also controls the bandwidth or range of each control. For example, if the center frequency is 30Hz, the control also affects frequencies as low as 20Hz and as high as 40Hz, although the affect is less at the extremes. A parametric equalizer can vary the bandwidth or range of control by making its affect wider or more narrow depending on needs or personal tastes.
Overall, if you need an audio equalizer, a parametric equalizer allows much more detailed control of the sound and permits finer adjustments.