13.3 Equalization Theory and Practice

Equalization is a powerful tool in mixing, shaping the frequency content of audio signals. It allows you to enhance or reduce specific frequency ranges, creating space for each element in the mix. Understanding EQ types, parameters, and techniques is crucial for achieving clarity and balance.

Effective EQ use involves both subtractive and additive approaches. Subtractive EQ removes unwanted frequencies, creating space for other elements. Additive EQ enhances desired frequencies, helping instruments cut through the mix. Mastering these techniques is essential for crafting professional-sounding mixes.

EQ Types

Parametric and Shelving EQs

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• Parametric EQ allows precise control over a specific frequency range
  • Adjustable parameters include center frequency, gain, and bandwidth (Q)
  • Useful for surgical EQ adjustments (removing unwanted resonances or feedback)
• Shelving EQ affects all frequencies above or below a set frequency
  • High shelf boosts or cuts high frequencies (cymbals, airiness)
  • Low shelf boosts or cuts low frequencies (bass, kick drum)

Filters

• High-pass filter (HPF) removes low frequencies below a set cutoff point
  • Helps clean up muddy or boomy low end (rumble, plosives)
  • Commonly used on vocals, guitars, and overhead mics
• Low-pass filter (LPF) removes high frequencies above a set cutoff point
  • Reduces harshness or sibilance (de-essing vocals)
  • Creates a darker, warmer sound (vintage effect)
• Notch filtering precisely removes a narrow frequency range
  • Eliminates specific problem frequencies (electrical hum at 60Hz)
  • Requires careful adjustment to avoid affecting surrounding frequencies

EQ Parameters

Q Factor and Resonance

• Q factor determines the width of the frequency range affected by an EQ band
  • Higher Q values create a narrower, more focused boost or cut
  • Lower Q values affect a wider range of frequencies
• Resonance occurs when an EQ band is boosted with a high Q value
  • Creates a peak or spike in the frequency response
  • Overuse can lead to an unnatural, ringy sound

Frequency Spectrum

• The frequency spectrum refers to the range of audible frequencies (20Hz-20kHz)
  • Low frequencies (20-250Hz) contain bass and sub-bass information
  • Mid frequencies (250Hz-4kHz) are crucial for instrument balance and vocal clarity
  • High frequencies (4kHz-20kHz) provide air, sparkle, and definition
• Understanding the frequency spectrum is essential for effective EQ decisions
  • Knowing which frequencies to boost or cut for each instrument
  • Identifying and resolving frequency masking or clashing between tracks

EQ Techniques

Subtractive EQ

• Subtractive EQ involves cutting or reducing unwanted frequencies
  • Removes muddy, boxy, or harsh elements from a sound
  • Creates space in the mix for other instruments to sit properly
• Common subtractive EQ targets:
  • Low-mid mud (200-500Hz) in guitars, vocals, and busses
  • Harsh upper-mids (2-4kHz) in vocals, guitars, and cymbals
  • Rumble or boominess (20-100Hz) in most instruments

Additive EQ

• Additive EQ involves boosting or enhancing desired frequencies
  • Brings out pleasant or characteristic elements of a sound
  • Can help instruments cut through a dense mix
• Common additive EQ targets:
  • Low-end weight (60-120Hz) in kick drums, bass, and sub-bass
  • Presence and clarity (1-6kHz) in vocals, snares, and leads
  • Air and sparkle (8-20kHz) in vocals, cymbals, and master bus
• Additive EQ should be used sparingly to avoid overcrowding the frequency spectrum
  • Subtractive EQ is often preferred for creating mix clarity and headroom