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What is Equalization/ EQ?
The actual proportional balance of frequencies in relation to each other at a given time is called “the Equalizationâ€.
The act of changing the loudness of the frequencies in relation to each other is called “Equalizationâ€. It is a procedure where we use an instrument called an Equalizer, it enables us to locate and adjust the volume level of any frequency at any point in the frequency range without any great affect on neighboring frequencies creating changes in the timbre of musical instruments and sounds. buy soma online
Why the need for Equalization?
Sound recordings are not perfect as they have distortions in the frequency balances caused by the reproduction process, the acoustics of the listening room and the nature of our hearing. We use sound-Equalization to restore the balance of the frequencies of the sound-reproduction to that of the original source.
Dr. Charles Paul Boner is credited with the first real steps in the development of technology for Equalization purposes back in the fifties and sixties. Dr. Boner would measure the frequency response of a sound system in a particular location by sweeping through the frequency spectrum and writing down the result for each frequency emerging from the system. He would then calculate with a slide rule the broad band filters necessary to reshape the systems response, to boost and cut particular frequencies to bring about an even frequency response. He used inductors, capacitors and resistors soldered together to create bands of equalization. Once he was contented with the broadband EQ he would do the same thing with narrow band filters to notch out feedback frequencies. It could take up to a week to complete the process. Dr. Boner trained Don Davis in this process. Don asked an electrical engineer at Altec to help him design a better, faster way to complete the process. He was aware that EQ differences of less than 1/3-octave were not heard as tonal differences by the human ear. He asked the engineer to build a set of factory built filters set at 1/3-octave intervals to match the response of the hand build broadband filters. They were granted a patent on the system sold by Altec as Acousta-Voicing. Don realized that he could shorten the time required to equalize further if he could look at all the frequencies at once. He asked HP if it was possible to design an instrument at 1/3-octave intervals that could analyze the sound in “real time†thus avoiding the need for sweeping the frequency range. HP took his inquiry as an order and called him some time later to say the instrument was ready and cost 20,000 dollars. Altec, whom he worked for, refused to pay so he had to mortgage his house to pay for the instrument. Altec bought the instrument from Don two years later after seeing the improvement it made to the equalization process. Altec and HP then formed a partnership to develop a 2,000-dollar version. With a market created, other firms began producing instruments for equalization (Equalizers) and frequency analysis. (1999 Rayburn)
Equalizer:
An Equalizer is an electronic processor designed to deliberately alter the tonal quality of audio passing through a number of filter circuits. The instrument applies gain to audio signals within a specific frequency range – positive gain (boost) and negative gain (cut).
High-pass & Low-pass Filters:
A high-pass filter (low-cut filter) progressively reduces the level of any audio frequencies below a user-specified ‘cutoff’ frequency. A low-pass filter (high-cut filter) reduces the level of frequencies above the ‘cutoff’ point. The definition of the cutoff point of a filter is the point at which there is 3dB of gain reduction. The increase in gain reduction occurs smoothly, only becoming more regular well below the cutoff point.
Shelving Filters:
A shelving filter is designed to apply an equal gain change to all frequencies beyond a user-selected shelving frequency, rather than applying a progressive gain change beyond a cutoff point like High and Low-pass filters do. These filters have a control for selecting the shelving frequency and one for selecting the amount of cut or boost to be applied.
Peaking Filters (Bell EQ):
To affect a frequency band that isn’t at either extreme of the frequency spectrum, a peaking filter is required. This type of filter allows you to selectively emphasize (boost) or attenuate (cut) a limited band of the audio spectrum. At least two controls are required, one to set the applied gain and one to specify the center-frequency of the band to be treated. More advanced equalizers have a third control called Resonance, Bandwidth or Q which alters the width of the band of frequencies to be affected by the filter.
Semi-parametric Equalizer:
When High and Low shelving filters are combined with a variable frequency peaking filter to control the tonal characteristics of the mid-frequencies the configuration is know as a semi-parametric Equalizer. (Peaking filter bandwidth set by the designer.)
Picture of a Semi-parametric Equalizer
Parametric Equalizer:
Parametric Equalizers can consist of dedicated High and Low shelving filters but will have at least one variable peaking filter to control the tonal characteristics of the mid frequencies with the user in control of the bandwidth (Resonance). In the digital domain there are up to five bands of fully parametric EQ.
Picture of a Parametric Equalizer
Graphic Equalizer:
The graphic Equalizer consist of a bank of sliders for boosting and cutting different frequencies of sound ranging from 20Hz to 20kHz which is the range of human hearing.
Picture of a Graphic Equalizer
All Equalizers introduce their own tonal characteristics during the recording and playback processes and sound engineers seek out particular instruments because of this. In the future designers of EQ in mixing consoles and outboard units will start paying more attention to the sound of the EQ rather than the technical aspects. Manufactures have started dropping the standard Low, Mid and High labels introducing more artistic expressions like ‘bottom’, ‘sheen’ and ‘glow’. This leads to more focus on the sound the equaliser produces. The Equaliser once seen as electronic equipment is now seen as an electronic musical instrument.
The Crucial Role of the Quality of the Music in our Lives - 1984 The Anstendig Institute
Sound-Equalization in Relation To the Way We Perceive Sound - 1984 The Anstendig Institute
The Massing of Overtones in Sound Reproduction - 1983 The Anstendig Institute
EQ - How and When to use it - SOS 1995 Mellor
Equalizer History & Why One is Better Than Another - 1999 Rayburn
Equalizers Explained - SOS 2001 White & Senior
Using Equalization - SOS 2001 White & Senior
