Parametric Equalizer

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

History of Parametric Equalizers

The 1950's saw the growth of equalizers as an audio production tool. Until the 1970s, if any equalizer existed, it had fixed center frequencies. Graphic equalizers were famous until then, 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 frequency selection and gain in three overlapping audio bands. The following year (1972), George Massenberg, 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 parametric equalizers in the live music scene and studio. The rest is history.  

Parameters Explained

• Center Frequency: The parametric equalizer allows users to select any particular frequency. This variable frequency is called the Center Frequency. This is a fascinating feature because it makes the equalization process 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 cuts or boosts any frequency by +/- 6dB or +/- 12 dB. 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. The Gain function offers this control.  

• Bandwidth: Bandwidth is the frequency range between -3 dB points on either side of the center frequency. Simply put, other frequencies above and below are also affected when a particular frequency is altered. This range of frequencies around the center frequency is known as the 'bandwidth.' Bandwidth has an inverse relationship to 'Q.' The higher the 'Q' narrower the bandwidth, the lower the' Q,' the wider the bandwidth. PS: Wider bandwidths tend to sound more natural than lower bandwidths.

Interesting Applications

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

• Feedback Cancellation: Shrieking sounds are heard in live music venues because the microphone picks up sounds from the speaker. To prevent this, a parametric equalizer can cut specific frequencies, solving the problem.  

• Tuning Studio Monitors: Any sort of speaker has peaks and dips at specific frequencies. For home studio applications, one requires speakers with flat responses. 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 sounds, piano pedals, etc., making the recordings sound cleaner.  

Additional Resources & Source Texts

• Parametric Equalizers
• What's The Frequency?
• A Short History of Graphic and Parametric Equalization