In addition to controllling bass and treble, it has the ability to raise and lower the level of a given frequency. A parametric equalizer is useful in pulling certain frequencies above the noise in a tape.
An equalizer with one or more "bands"; each having a control for frequency, bandwidth, and level. With such an equalizer, one can zero in on a specific frequency or range of frequencies and then cut or boost as desired. Some parametric equalizers on mixers and some outboard gear only provides control over the frequency and level, but not the bandwidth. These are called semi-parametric equalizers. see graphic equalizer
A type of audio equalizer having several "parameters" for control of various filters that can be applied to audio signals. Parametric equalizers are most widely used in situations where very fine control over the audio signal is desired, and provide control over gain, Q (Quality factor, a measure of a resonant system), and frequency.
Keywords:  subwoofer
a must for every subwoofer