As the name suggests, Parametric Equalizer helps to edit different parameters of an audio spectrum. It has three main parameters: gain (amplitude), center frequency and bandwidth (inverse of ‘Q’). Unlike Graphic equalizer, it has variable center frequency. This feature allows the user to alter any specific frequency thus making the equalization process very customized. This equalizer is capable of very fine adjustments; hence it is widely used in the market.

 

History of parametric equalizers

 

1950’s saw the growth of equalizers as an audio production tool. Until 1970’s if any kind of Equalizer existed it had fixed center 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 arbitrary selection of frequency and gain in three overlapping audio bands. The following year (1972) George Massenberg, who was still a teenager, wrote a paper to AES in Los Angeles concerning parametric EQ and it’s use in music production. That year saw the rise of parametric equalizer in the live music scene and studio. The rest is history.

 

Parameters explained

 

  • Center Frequency

 

The parametric equalizer allows the user to select any particular frequency. This variable frequency is called the Center Frequency. This is a pretty fascinating feature because it makes the process of equalization very precise. Until the birth of parametric equalizers, mix engineers used to deal with fixed center frequencies, which did not allow for precise equalization.

 

  • Gain (Amplitude)

 

A parametric equalizer cut or boost any frequency by +/- 6dB or +/- 12dB. The control that allows for this is the ‘gain or amplitude knob’

In simple words once we have chosen a center frequency in order to cut or boost it we need some sort of control. This control is offered by the Gain function.

 

  • Bandwidth

Bandwidth is the frequency range between -3dB points located on either side of the center frequency.

Simply put, when a particular frequency is altered, other frequencies that are above and below it also get affected. This range of frequencies around the center frequency is known as the ‘bandwidth’.

Bandwidth has an inverse relationship to ‘Q’. Higher the ‘Q’ narrower is the bandwidth and lower the ’Q’ wider is the bandwidth.

 

PS: Wider bandwidths tend to sound more natural than narrower bandwidth’s.

 

Interesting Applications

 

Other than mixing and making tonal changes to instruments these are some other application of parametric equalizers.

 

  • Feedback Cancellation

Shrieking sounds are heard in live music venues, because of the microphone picking up sounds from the speaker.  To prevent this, 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.

 

Additional Resources & Source Texts

 

http://www.yamahaproaudio.com/global/en/training_support/selftraining/pa_guide_beginner/equlizer/

http://www.mediacollege.com/audio/eq/parametric.html

http://www.soundonsound.com/techniques/whats-frequency

https://intelligentsoundengineering.wordpress.com/2016/02/22/a-short-history-of-graphic-and-parametric-equalization/