The birth of a Parametric EQ


1950’s saw the growth of equalizers as an audio production tool. Until 1970’s if any kind of Equalizer existed it had fixed centre frequencies. Graphic equalizers were pretty famous until that point but people wanted to break out of this fixed frequency constraint. In 1971, Daniel Flickinger invented a tunable equalizer called ‘ Sweepable EQ’. As the name suggested, this equalizer could make an arbitrary selection of frequency and gain in three overlapping audio bands. The following year (1972) George Massenburg, who was still a teenager, wrote a paper to AES in Los Angeles concerning parametric EQ and its use in music production. That year saw the rise of a parametric equalizer in the live music scene and studio. The rest is history.


What is a Parametric Equalizer


Parametric equalizers are multi-band variable equalizers which allow users to control the three primary parameters: amplitude, centre frequency and bandwidth. The amplitude of each band can be controlled, and the centre frequency can be shifted, and bandwidth (which is inversely related to “Q”) can be widened or narrowed. Parametric equalizers are capable of making much more precise adjustments to sound than other equalizers. They are commonly used in sound recording and live sound reinforcement. Parametric equalizers are also available as standalone outboard gear units.


Variable Frequency Selection Control


On a parametric equalizer, the frequency selection control is always continuously variable over the over a wide band of frequencies. In addition to having a selectable frequency and variable amplitude, the parametric equalizer offers variable Q. This allows the engineer to select the width of the bell-shaped curve for boosting or attenuating. For convenience, the width is usually in terms of octaves. However, some manufacturers design it as Q.

Q values commonly range from a wide ban of four octaves down to a narrow band of half an octave. These may be continuously variable or switch selectable between the two bandwidth extremes. Therefore, a parametric equalizer allows the engineer to select the amount of boost or cut, the centre frequency of the equalization curve, and the Q, or bandwidth of the curve. A typical outboard of parametric equalizer has two channels or four bands full parametric equalization. Each band can be switched on and off individually. In addition, most of the parametric equalizers possess a bandpass filter.


Useful applications


Some of the useful applications of the parametric equalizer are :

– Feedback cancellation – Shrieking sounds are heard in live music venues, because of the microphone picking up sounds from the speaker.  To prevent this, the parametric equalizer can cut certain frequencies hence solving the problem

– Tuning studio monitors – Any sort of speaker has peaks and dips at certain frequencies. For home studio applications one requires speakers with flat response. Parametric equalizers can also flatten out these peaks and dips.

– Eliminating unwanted noises – Producers often use Parametric equalizers to cancel out noises like guitar pick sound, piano pedal etc. making the recordings sound cleaner.


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