Equalization Changing the curve

What is an EQ? An Equalizer –Is generally a frequency-specific amplifier –Is made up of filters (passive or active) –Is one of the most powerful tools an engineer has

A bit more about frequency Most sounds are made up of a spectrum of frequencies (i.e. not one single frequency) The lowest frequency in the spectrum is called the fundamental. This is usually the perceived pitch Other frequencies are called overtones. These can be classified as harmonics or partials Joe Fourier: “any complex periodic wave can be synthesized from sine waves of different frequencies, amplitudes, and time relationships” Source: Master Handbook of Acoustics; F.Alton Everest

Example FFT Insert Sound File Here

Frequency “Bands” “Band” refers to a group or range of frequencies –The FM broadcast band ranges from 87.5 MHz to MHz “Bandwidth” defines the size of the range –the bandwidth of human hearing is approximately 20 kHz

What we hear 20 Hz100 Hz200 Hz1 kHz3 kHz8 kHz10 kHz20 kHz500 Hz Fundamentals of most instruments Presence, sharpness Clarity ->Air “sizzle” crispness Impact, rumble, deep bass, “size” Low FrequenciesLow “Mids”High “Mids”High Frequencies

Basic Filter Concepts A basic filter generally does not amplify Attenuate – “to weaken” – Webster’s II New Riverside Dictionary Pass band – range of frequencies the filter will not attenuate Stop band – range of frequencies that will be attenuated by the filter Corner or Cutoff frequency – essentially the border between the pass band and stop band. Attenuation is -3dB at this frequency Are measured by “n th order” where n represents 6 dB per octave attenuation –1 st order = -6dB per octave slope –2 nd order = -12dB per octave slope Types of filters –High pass (low cut) –Low pass –Band pass –Notch Active Filters can amplify or attenuate

Shelving Filters A shelving filter can boost or cut –A low shelf will boost or cut all frequencies below the cutoff frequency –A high shelf will boost or cut all frequencies above the cutoff frequency Bass and Treble controls on most consumer stereo equipment are shelving filters

“Peak-and-dip” filter Amplifies or attenuates a band centered on a particular frequency Q – the bandwidth of the frequencies being effected –Higher Q value means narrower band

Types of Equalizer

A number of “peak-and-dip” filters with fixed Q and center frequency Generally used in live sound situations to “tune” the room and control feedback Commonly have up to 30 filters (bands) with a 1/3- octave bandwidth Graphic EQ

Parametric EQ Allows you to control the frequency and bandwidth (Q) of the filter Most powerful type of EQ for tone shaping Usually only a few bands