Mixing and EQ

Overview & Objectives

Introduce the concept of equalization and its historical evolution.
Compare different types of EQ tools (parametric, graphic, dynamic, shelving, etc.).
Explain the audio frequency spectrum and how EQ interacts with it.
Demonstrate practical techniques for tone shaping, problem solving, and creative sound design.
Highlight EQ’s role in mixing, mastering, live performance, and sound design.

Historical Context

Analog beginnings: Early equalizers were built into analogue consoles for radio and film work.
Graphic EQ: Introduced in the 1950s with multiple fixed bands controlled by sliders.
Parametric EQ: Invented in the 1970s, offering variable frequency, bandwidth (Q), and gain.
Digital EQ: Modern DAWs include visual interfaces, dynamic automation, and linear-phase processing.

Equalization uses

Tone Shaping.
Fixing frequency problems.
Balancing instruments in a mix.
Enhancing clarity and presence.
Removing unwanted noise.
Creating special effects.

Tone Shaping: EQ is often used to shape the tonal characteristics of a sound source. You can boost or cut specific frequency ranges to make an instrument or voice sound warmer, brighter, or more natural.
Fixing Frequency Problems: Sometimes, audio recordings or live sound environments can have unwanted resonances, hums, or noise in certain frequency ranges. EQ can be used to reduce or eliminate these issues.
Balancing Instruments: In a mix, different instruments and vocals can clash in terms of frequency content. EQ helps in carving out space for each instrument and making sure they don’t step on each other’s sonic territory.
Enhancing Clarity: By boosting the high frequencies (treble) of a signal, you can increase clarity and presence, making it easier for the listener to hear details in the sound.
Removing Unwanted Noise: EQ can be used to roll off low frequencies that might contain rumble or wind noise. High-pass filters are a common tool for this purpose.
Creating Special Effects: Extreme EQ settings can be used creatively to achieve special effects like a telephone voice (narrow bandpass), a radio broadcast sound (filtered high frequencies), or a vintage vinyl record effect (boosting certain frequency ranges while cutting others).

Correcting room acoustics.
Preventing feedback in live sound.
Matching the sound of different sources.
Finalizing audio mixes (mastering).
Sound design for media.
DJ mixing.
Optimizing live performance sound.

Room Correction: In audio production, it’s important to ensure that the playback environment doesn’t color the sound. Room correction EQ systems can analyze the room’s acoustics and apply EQ to compensate for any uneven frequency response caused by the room itself.
Feedback Control: In live sound reinforcement, EQ can be used to prevent feedback by notching out frequencies that are prone to feedback in a particular room or setup.
Matched EQ: You can use EQ to match the tonal characteristics of two different audio sources, like matching the sound of two guitar amplifiers or blending two different microphone recordings of the same instrument.
Mastering: In the final stages of audio production, mastering engineers use EQ to fine-tune the overall tonal balance of a mix and prepare it for distribution.
Sound Design: Sound designers for film, video games, and other media use EQ to shape and manipulate audio elements to create specific atmospheres, textures, and moods.
DJ Mixing: DJs use EQ on their mixers to blend songs smoothly by adjusting the bass, midrange, and treble frequencies of two tracks to match.
Live Performance: Musicians and bands often use EQ on their instruments and vocal channels to optimize their sound in a live setting, adapting to the acoustics of the venue.

Types of Equalizers

Parametric EQ – Continuously variable frequency, gain, and bandwidth.
Graphic EQ – Fixed frequency bands with sliders for broad adjustments.
Dynamic EQ – EQ that responds to signal level for automated boosts/cuts.
Shelving EQs – High- and low-shelf filters boost or cut all frequencies above or below a cutoff.
Filter Types – High-pass, low-pass, band-pass, notch, and bell curves (peaking filters).

Audio Frequency Spectrum

Sub/Low (20 Hz – 250 Hz) – Weight and power; sub-bass and bass.
Low Mids (250 Hz – 500 Hz) – Fullness of rhythm instruments and warmth of voice.
Mids (500 Hz – 2 kHz) – Core harmonic content; presence and punch.
High Mids (2 kHz – 4 kHz) – Clarity and definition; attack and articulation.
Highs (4 kHz – 20 kHz) – Air and sparkle; cymbals, string brilliance, vocal breathiness.

EQ Controls

Frequency Selection – Choose the precise frequency band to adjust.
Gain – Boosts or cuts the level of a selected frequency band.
Quality Factor (Q) – Controls bandwidth of the adjustment.
Filter Type – High-pass, low-pass, band-pass, notch, shelving, or bell.

Filter Types & Techniques

High-Pass Filter – Removes low-end rumble.
Low-Pass Filter – Cuts high frequencies.
High/Low Shelf Filters – Boost or cut all frequencies above/below a cutoff.
Bell (Peaking) Filter – Boosts or cuts around a central frequency.
Notch Filter – Removes narrow resonant frequencies.
Band-Pass Filter – Allows only a specific frequency range.

Band	Range	Characteristics
Low (Sub & Bass)	20 Hz – 250 Hz	Adds weight and warmth
Low Mids	250 Hz – 500 Hz	Thickness and body
Mids	500 Hz – 2 kHz	Core harmonic content
High Mids	2 kHz – 4 kHz	Clarity and articulation
Highs	4 kHz – 20 kHz	Air and sparkle

Guess the Range

I’ll play a sound clip, and you guess which frequency range was boosted or cut.
You don’t need to specify exact frequencies, just the general band (e.g., Low, Low Mids, Mids, High Mids, High).

Additional Resources

Frequency Cheatsheet

Reaper Effects Guide

Wrap-Up & Takeaways

EQ is a foundational tool for shaping, balancing, and enhancing audio.
Understanding frequency bands and filter types is essential.
Subtractive EQ should generally precede additive EQ.
Creative EQ techniques can evoke environments and textures.
Practice and critical listening are key to mastering EQ.

Equalization uses

Adjusting sound tone.
Fixing frequency problems.
Balancing instruments in a mix.
Enhancing clarity and presence.
Removing unwanted noise.
Creating special effects.

In audio and sound engineering, “EQ” stands for equalization. Equalization is a fundamental tool used to adjust the balance of frequencies in an audio signal. EQ is used for a variety of purposes in audio production, live sound reinforcement, and music mixing. Here are some common uses of EQ in audio:

Tone Shaping: EQ is often used to shape the tonal characteristics of a sound source. You can boost or cut specific frequency ranges to make an instrument or voice sound warmer, brighter, or more natural.
Fixing Frequency Problems: Sometimes, audio recordings or live sound environments can have unwanted resonances, hums, or noise in certain frequency ranges. EQ can be used to reduce or eliminate these issues.
Balancing Instruments: In a mix, different instruments and vocals can clash in terms of frequency content. EQ helps in carving out space for each instrument and making sure they don’t step on each other’s sonic territory.
Enhancing Clarity: By boosting the high frequencies (treble) of a signal, you can increase clarity and presence, making it easier for the listener to hear details in the sound.
Removing Unwanted Noise: EQ can be used to roll off low frequencies that might contain rumble or wind noise. High-pass filters are a common tool for this purpose.
Creating Special Effects: Extreme EQ settings can be used creatively to achieve special effects like a telephone voice (narrow bandpass), a radio broadcast sound (filtered high frequencies), or a vintage vinyl record effect (boosting certain frequency ranges while cutting others).

Correcting room acoustics.
Preventing feedback in live sound.
Matching the sound of different sources.
Finalizing audio mixes (mastering).
Sound design for media.
DJ mixing.
Optimizing live performance sound.

Room Correction: In audio production, it’s important to ensure that the playback environment doesn’t color the sound. Room correction EQ systems can analyze the room’s acoustics and apply EQ to compensate for any uneven frequency response caused by the room itself.
Feedback Control: In live sound reinforcement, EQ can be used to prevent feedback by notching out frequencies that are prone to feedback in a particular room or setup.
Matched EQ: You can use EQ to match the tonal characteristics of two different audio sources, like matching the sound of two guitar amplifiers or blending two different microphone recordings of the same instrument.
Mastering: In the final stages of audio production, mastering engineers use EQ to fine-tune the overall tonal balance of a mix and prepare it for distribution.
Sound Design: Sound designers for film, video games, and other media use EQ to shape and manipulate audio elements to create specific atmospheres, textures, and moods.
DJ Mixing: DJs use EQ on their mixers to blend songs smoothly by adjusting the bass, midrange, and treble frequencies of two tracks to match.
Live Performance: Musicians and bands often use EQ on their instruments and vocal channels to optimize their sound in a live setting, adapting to the acoustics of the venue.