Equalization, or EQ as it is more commonly called, is a form of audio processing which is used to adjust the volume of a frequency or range of frequencies within the sound, it does this by cutting out unwanted frequencies and boosting others. It is incredibly useful as it helps to balance out sounds so that they work well with one another in a song. The history of EQ begins in the 1930’s when the first instance of it appeared being used in audio receivers and phonograph playback. It was during this time that John Volkman invented an external EQ, this allowed people to select certain frequencies and boost or cut them. EQ’s really rose to popularity in the 1950’s and 1960’s, mostly due to the invention of the Langevin EQ-251A, this was an early EQ which featured slide controls and which is now considered the precursor to graphic EQ as we know it today. The first actual graphic EQ was released by Art Davis. This EQ featured six bands which allowed for 8dB of boosting or cutting, zero insertion loss and had faders with 17 switches. After the release of this model Davis then moved to Altec where he invented the Model 9062A which was a seven band EQ. In 1958 Wayne Rudmose wrote a paper titled ‘Equalization of Sound Systems’ wherein he proposed that PA systems should be tested for frequency response, from this the equipment that allowed us to tune a PA system was created. It was also during this period of time that Rock ‘N’ Roll was becoming popular which meant that the music being played through these systems was become louder and more dynamic. In 1967 the Acousta-Voice system was released, this model was the first 1/3 octave passive notch filter and from this technology a 1/3 octave cut and boost graphic EQ were invented. Graphic EQ was popular and proving useful in a studio environment but the large faders required took up a lot of space so engineers wanted a smaller device which could be built directly into the channel strip of an analog mixing desk. In the early 1970’s Daniel Flickinger created a sweepable EQ which enabled mixing engineers to adjust the frequency and gain in three bands with fixed width. Then in 1972 George Massenburg added onto this by using the same idea but adding a device which let engineers adjust the frequency, gain and bandwidth which he named the Parametric EQ.

Intelligentsoundengineering (2017) A short history of graphic and parametric equalization, Intelligent sound engineering. Available at: https://intelligentsoundengineering.wordpress.com/2016/02/22/a-short-history-of-graphic-and-parametric-equalization/ (Accessed: 08 May 2023)

*N. (2022) View from the bench: Tracing the EQ path, AudioTechnology. Available at: https://www.audiotechnology.com/tutorials/view-from-the-bench-tracing-the-eq-path (Accessed: 08 May 2023)