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Equalization

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.

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Equalization

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  1. Equalization Changing the curve

  2. 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

  3. 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

  4. Example FFT Insert Sound File Here

  5. Frequency “Bands” • “Band” refers to a group or range of frequencies • The FM broadcast band ranges from 87.5 MHz to 108.0 MHz • “Bandwidth” defines the size of the range • the bandwidth of human hearing is approximately 20 kHz

  6. What we hear Impact, rumble, deep bass, “size” Fundamentals of most instruments Presence, sharpness “sizzle” crispness Clarity ->Air 20 Hz 100 Hz 200 Hz 500 Hz 1 kHz 3 kHz 8 kHz 10 kHz 20 kHz Low Frequencies Low “Mids” High “Mids” High Frequencies

  7. 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 “nth order” where n represents 6 dB per octave attenuation • 1st order = -6dB per octave slope • 2nd order = -12dB per octave slope • Types of filters • High pass (low cut) • Low pass • Band pass • Notch • Active Filters can amplify or attenuate

  8. 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 http://www.harmony-central.com/Effects/Articles/Equalization/

  9. “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 http://www.harmony-central.com/Effects/Articles/Equalization/

  10. Types of Equalizer

  11. Graphic EQ • 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

  12. 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

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