How does an Audio Equalizer work? An In-depth Guide

Most people are intimidated by audio mixer faders. This is an equalizer to control the frequency spectrum of an audio track. The role of audio equalizers began with hardware.

Early mixers with treble and bass equalizer knobs. They evolved to have multiple knobs for each band in a spectrum.

This revolutionized production studios in the early 1970s, leading to multi-band mixer boards with multiple faders.

This was the beginning of the end of knobs. The invention of such mixer boards revolutionized the quality of songs produced. It also demonstrated the power of post-production editing.

Before equalizers, the recorded sounds were always dependent on pre-recording sessions. Engineers were always under pressure to record flawlessly because post-production could only do so much.

The advent of mixers threw this out the window, allowing mixing engineers to do amazing things with audio tracks.

An audio equalizer works by adjusting the frequency bands of an audio track. Filters can manipulate these frequency bands to modulate the audio track.

Knowing that an audio equalizer works with frequencies isn’t enough. You must consider how it compares to other equalizers and its internal components.

In this article, I will explain what an equalizer is and how to avoid it. Let’s begin.

What is a leveler?

An equalizer is a piece of software or hardware that alters the frequency spectrum of an instrument.

Equalizers have helped mixing engineers make precise changes in the frequency spectrum.

Equalizers can work their way up the frequency spectrum from 20 Hz to 20 kHz.

Equalizers are used to clean up the low end of a high-pitched vocal and the high end of a bass guitar.

The equalizer’s ability to dramatically improve track quality revolutionized the music industry.

This improved side chaining, a technique for balancing two instruments that share the same frequency range.

Using an equalizer is underrated. You can easily and precisely remove low-frequency background noises from a track without affecting the actual vocal performance recorded in the track.

This precise ability to change makes equalization an important technique for a beginner music producer to learn.

Equalizers are mostly used to shape vocal performances. They are vital in making the song work with the background instruments. See our article on equalizing vocals.

Vocals are vital in music production. Even though the beat has more frequency weight, vocals are equalized more to fit between the instruments.

Cleaning up the vocals’ low end with an equalizer allows other instruments in the same spectrum to shine. Equalizer filters add dimension to a song’s elements.

Equalizers also help music producers eliminate low-frequency rumble that can be harmful to speakers and listeners.

Every vocal or instrument in a song has a frequency range. They start disrupting the song when they go out of range. Interference and phase issues cause distortion in the song.

A typical male voice ranges from 85Hz to 6 kHz. A female voice starts at 300Hz and goes up to 11 kHz.

Because male vocals have a lower end, you would need to use different techniques. The same goes for instruments.

Knowing where each instrument belongs in a frequency spectrum will help you as a music producer.

This is one of the reasons why experienced producers can change an instrument by ear.

Experience sets a music producer’s value rather than how many hits he has. Equalization is one of those areas in music production where a novice would feel lost.

Equalization is a complex process that requires years to master.

Equalization has evolved from faders and hardware in the last decade. We have software equalizers that can show every nuance of a song.

Software equalizers show the modulated instrument visually.

Hardware vs. digital equalizer

Equalization began with hardware. After dominating music studios in the 1970s, it migrated into all hardware sound systems.

By the end of the 1980s, the hardware was also in mixer boards, causing a huge shift in the industry’s mixing and mastering practices.

Equalizers are still used in recording studios for live musical recordings.

Using a hardware equalizer allows you to adjust and manipulate a group of frequency bands rather than a single frequency.

Hardware instruments add warmth and texture to a track that software instruments cannot.

Hardware instruments are easier to use than software instruments because they have fewer options and functions.

Most hardware equalizers have three to four knobs. The low end is usually controlled by a knob around 200-400Hz.

The next knob should be for the mid-range frequencies (800-1kHz) and another for the higher frequencies (11-15kHz). Some advanced hardware has 6–7 knobs that control different bandwidths.

The choice between a hardware and software equalizer is always debatable, but the benefits of software equalizers are clear.

The manipulation abilities of software equalizers make up for the lack of warmth and tonal harmony offered by hardware equalizers.

Software equalizers first appeared in audio production software around 1998 and advanced rapidly over the next decade.

As software equalizers evolved, so did their functions and modulations.

These new equalizer modulations revolutionized studio and software equalizer use.

Side chaining in the equalizer made a huge difference in how songs’ low end was optimized.

The thumping bass effect in songs is created by side chaining equalizers.

Modulation, like filters in software equalizers, allows for advanced instrument and vocal manipulation.

These filters in audio production software allow you to create a choir from a single vocal.

and equalization, introduced in software equalizers, has a huge impact on how songs are manipulated in audio production.

This is a huge change from previous equalization methods. Less hardware equalizer = more software equalizer.

Before software instruments and equalizers, hardware equalizers didn’t work well with compressors.

Compression was always routed via separate analog hardware. Software equalizers eliminated this.

Software equalizers made sure the compressors worked. There are even software equalizers with compression.

Techniques for both compression and equalization were introduced to the industry as multiband techniques. Software companies gathered them.

Multiband compression and equalization helped ease the transition from analog to digital software. The software instruments regained their warmth.

Compression and equalization allowed for more harmony in the tracks.

How to use an EQ?

Beginners should get their hands dirty and experiment with the software to learn about equalizers and the frequency spectrum.

You can follow some guidelines to reduce errors when doing your first equalization project.

Let’s look at some tips for getting started in equalization without too much difficulty.

With vocals, avoid drastic changes and instead focus on the low-end roll-off. The equalizer’s audio visualizer shows the vocal’s frequencies.

Simply put, roll off reduces everything below the vocal’s start point. Male vocals begin at 110Hz, female vocals at 280Hz.

It all depends on the singer. Starting with a roll off, find the sheen and high gain frequencies. Our detailed guide on how to equalize a vocal can be found here.

In piano, the frequency spectrum spreads from one end to the other, adding to the complexity. This is where people may feel intimidated.

The golden rule in equalization is to start with trial and error.

Make a small change and test it. If not, go back to the original and retry. The song’s feel is solely determined by the tonic relevance.

Equalization can drastically alter tonic relevance. A producer would lose all the intricate details and the heavy mid-region if they cut the piano’s frequencies from 700-1400Hz.

This is one of the reasons why when using equalizers for the instrument, you must be very careful with the changes you make.

To get the piano’s richness, roll off the low end like the vocals and boost the high frequencies by about 8 kHz.

Strings are a totally different animal than vocals and piano. This is one of the reasons why mastering the equalizer on each element of the track takes years.

Excessive frequency boost for string instruments results in harsh middle notes, destroying songs or creating annoying hissing sounds.

When recording a string instrument, such as a guitar, the resonance and instrument taps are recorded.

Unwanted frequency boosting causes an unpleasant sound. For strings, always roll off the low end and work your way up to the mids to find excessive resonance.

Find a resonance in the song’s audio spectrum and gently push it down with a bell curve. Using a subtractive approach, you lower the unnecessary high frequencies, allowing the important ones to shine through.

Drums are also a different story. In any song, the lower end of the drum spectrum is heavier than the higher end.

Using an equalizer should be used to optimize the low end of the drums.

Any addition or subtraction should be done mostly at the bottom. The drum usually has a high-end cut and a low-end boost.

Unlike other instruments and vocals. For bass, it’s more like drums, where you boost the low end and roll off the high end.

Why use graphic equalizers?

Graphic equalizers outperform software or hardware equalizers with just knobs. Graphic equalizers will help you understand the software’s frequency work.

Analog software and hardware equalizers cannot do this. Graphic equalizers allow you to see which frequencies you are boosting.

You will be able to identify the track’s flaws. Using a graphic equalizer allows any music producer to equalize properly.

The graphic equalizer’s intuitive nature will immerse the user in the experience rather than separate them from it. Other analog and analog-based software equalizers cannot do this.

Immersion allows you to learn a song by heart.

Visualizing the song will help you recall previous experiences with audio equalization, allowing you to gain more experience.

Multiband compression and equalization are best done with a graphic equalizer. An analog equalizer will not have any references when using frequency bands.

Using a graphic equalizer, you can see which bands are being compressed and which are being boosted.

Thanks to software innovation, this is a step up from previous music production techniques.

Working with a graphic software equalizer also allows for precision that is not possible with analog equalizers.

The ability to fine-tune which frequencies to boost and how much boost to apply makes the software equalizer more appealing.

Producers still prefer analog equalizers for sound harmonization and warmth. It will be difficult for analog equalizers to make a comeback in an age of graphic equalizers.

Equalizer filters

Filters are part of an equalizer’s structure. They aid in track additive and subtractive equalization. Each filter is designed to only affect the targeted frequency.

This is the main analog vs digital equalizer difference. A digital equalizer offers more value for money. Filters can also be saved as presets in a software equalizer, speeding up the mixing and mastering process.

It is possible to assign these presets to a specific track or even a small frequency spectrum, eliminating the need to duplicate the process in software.

If you record a lot of the same artist, you can save their preset and avoid the tedious process of equalizing everything from scratch.

Examine each of the following filters.

Low pass

From right to left, a low-pass filter sweeps frequencies It cleans up the high end of a spectrum. The low pass can be used to clean up unwanted high end. This ensures the track is free of harsh high-end sounds that harm the track.

A high cut filter is a low pass filter. It shaves the top and moves left to right. The low pass filter is useful for instruments with excessive white noise in the high frequency range.

When using a low pass, make sure the total gain in dB is less than 6. Anything higher will boost the master volume, possibly causing clipping.

High pass

Left-to-right frequency sweeping with a high-pass filter It cleans up the low end of a spectrum. The high pass filter can be used to clean up unwanted low end. This removes unnecessary bass heavy low-end sounds from the track.

Also known as a low cut filter, So it moves from left to right. The high pass filter can be used on instruments with too much bass rumble.

With a high pass filter, make sure the total gain is less than 6 dB or you’ll end up boosting the master volume. The song may clip as a result.

Bell Curve

The bell curve is not like the high pass or low pass filters. A bell curve has both high and low pass filters, so it has a high boost in the middle. This filter can boost a specific frequency or a range of frequencies.

Bell curves are great when working with complex instruments and unsure which frequencies to boost. It analyzes frequencies better than a high pass or low pass filter alone.

The bell curve also helps when scanning the frequency spectrum for resonant frequencies. These resonant frequencies cause harsh sounds that degrade the track.

Using a steep bell curve and lowering the gain will help you find these resonant frequencies. The songs get better as you get better at finding the resonant frequencies.

When using a bell curve, make sure the total gain dB is less than 6 to avoid clipping.

So how do you clear the sound with equalizer?

Clearing the sound involves sweeping it from right to left or vice versa. Many music producers use this technique to cut sounds from a song. A low pass or high pass filter can help.

Which equalizer setting for bass?

When EQing for bass, always boost frequencies between 110-180Hz and lower frequencies between 400-600Hz. This allows for a balanced mid-range and low-end with dominant bass.

Which equalizer is best?

The best equalizers on the market today are digital equalizers that display a visual representation of all frequencies in an audio spectrum. This allows the mixing engineer to make more precise changes and manipulations.

How to properly equalize

A reference track is required for proper equalization. Always compare your changes. This method helps you develop a musical ear.

Less is more also applies to equalization.


It takes time to master audio equalization. There is no better way to learn than to do it yourself. It takes practice to identify and correct errors.

To make an audio equalizer work wonders in your project, you need patience and focus on each track.

Making mistakes and learning from them helps you improve as a mixing engineer or music producer.