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Not All EQs Are Made Equal: 9 EQ Types Explained

Jul 01, 2024

In an oversaturated market, the difference between EQs can often be minimal, but your signals will benefit from knowing where the real distinctions lie.

Not All EQs Are Made Equal: 9 EQ Types Explained

As a music producer or mixing engineer, you’ve probably got a go-to parametric EQ. That might be the one that comes with your DAW, or it might be something like Waves F6 that boasts some extra bells and whistles. Advanced parametric EQ features might include dynamic functionality with internal or external sidechain controls, mid/side functionality or global mix control.

Sonically, though, the basic digital EQ curves in any given parametric EQ all sound pretty much the same. So why is there so much choice when it comes to equalizers? The answer is that analog-style EQs, and the hardware they are modeled on, each have their own quirks and tonal qualities that give them a distinctive character.

In this article, we’ll be uncovering nine types of equalizer, what sets them apart from one another, and when each of them might be the most suitable for your needs.

1. Early Equalizers

While us creatives mostly think of EQ as being a music production tool, the foundations of the process are actually found in radio broadcasting. In the 1920s, radio engineers used electrical-mechanical devices to adjust the level of specific frequency bands. The Radio Corporation of America (RCA) developed one of the first widely used equalizers, the RCA 8B. No prizes for guessing how many bands of equalization it had!

Another innovative piece of equalization equipment was the Abbey Road RS56, a completely passive device that was the first fully parametric EQ in the world. It was designed to be deployed after recording and production, but before the record hit the radio airwaves – a process that we would now describe as mastering.

Although they were designed with mastering in mind, engineers quickly worked out that RS56s were more versatile and usable than the EQs found on consoles at that time. The downside was that they were also bulky, expensive and inaccessible. There were only two RS56 units ever made.

If you’re not lucky enough to own one of those legendary mastering units, you can opt for the Waves emulation of the same device. Having been developed alongside Abbey Road themselves, this plugin gives you a flavor of the smooth and transparent sound of the original RS56.

2. The Pultec EQP-1A

Like the RS56, the Pultec EQP-1 and its many variations were based on passive EQ circuits which gave them a smooth and musical sound. While the circuit was passive, much of the tone and character of the Pultecs could be attributed to the amplifier that was necessary to boost the signal back to its original level.

Thanks to the valve-based amplifier, engineers found that merely running a signal through a Pultec added a certain amount of pleasant distortion, before they’d even applied any equalization. Engineers also found that the manual advised against simultaneously cutting and boosting the low end, but doing so actually improved the clarity and impact of kicks and basses. This technique is now cemented in the sound engineering history books as “The Pultec Trick”.

One downside with most of the Pultec devices was that they were mono, meaning you’d need two if you wanted to process a stereo signal. Once again, this isn’t a cheap solution, but the Waves PuigTec EQs is a wallet-friendly alternative. Not only do you get a meticulously modeled plugin of the Pultec EQP-1A (with added stereo functionality), you also get the MEQ-5 midrange equalizer.

3. Advanced Passive EQs

The equalizers we’ve discussed thus far have all been passive, and relatively limited in terms of their controls, but the Chandler Curve Bender and Manley Massive Passive buck that trend. Although both devices were passive, they added more capability than could be found on their predecessors.

For starters, both EQs offered identical controls for the left and right channel, making them stereo. They also introduced the ability to change the shape of certain bands between bell and shelving filters, as well as independent high and low pass filters for even further control over your signal.

4. The British Legends of Equalization

You might have heard the term “British EQ” bandied around in the past, but what exactly does that mean? British EQ refers to any equalization device designed to resemble classic British-made EQs from the likes of Neve, SSL and others.

Waves Scheps 73 EQ plugins

From Neve’s 1073 and 1081 to SSL’s E and G-Series EQs, the range, breadth and heritage of British EQs is vast. Despite being relatively limited in its feature set, the 1073 is widely regarded as having the most desirable sound of just about any preamp and EQ in history. On the other side of the coin, something like the SSL G-Equalizer gives you a much smoother and more transparent sound than a 1073, and with much greater control.

Once again, investing in hardware classics like the above might be outside of the realms of many, but there are plugins such as the SSL E-Channel Strip and Scheps 73 that offer that sound and functionality present in the physical versions.

5. Digital Equalization

Plugins are all but essential for anyone wishing to create music today, but that wasn’t always the case. During the 90s, digital and software-based tools were being drip-fed into the market, and one of the most important tools of all was the Waves Q10 Equalizer.

Launched in 1992, the Q10 was not only Waves’ first product, it was the world’s first commercially available third-party audio plugin. This was clearly a huge moment for music technology, but also for equalization too. With 10 bands of EQ which could be set to one of six possible shapes, the Q10 offered unprecedented levels of control and precision compared to EQs that came before it.

Waves Q10 EQ Plugin

In order to keep up with the times, the Q10 has undergone a number of renovations in the past 30 years. As a result, the Q10 holds its appeal as the choice EQ for many music producers and sound engineers around the world.

6. Linear Phase EQ

As demonstrated by the Q10, the evolution of digital signal processing made advanced equalization more accessible to more people, but there were some side effects of the technology. Phase smearing is caused by the inherent latency in traditional minimal phase EQs when equalization is applied.

Linear phase EQs differ in that they are designed to retain the phase relationship in the audio signal across the entire frequency range. While the phase incoherence caused by minimum phase EQs is usually inaudible, there are instances where you may opt to use a linear phase EQ in order to retain the phase relationship. These instances might include during mastering, while applying particularly extreme filtering, or while applying EQ to multi-mic’d sources such as orchestras or bands.

Waves Linear Phase EQ is a transparent and efficient linear phase EQ, designed to let you apply equalization with the peace of mind that your signal’s phase will remain unaltered. The simple interface and five bands of parametric EQ will be familiar to users of other parametric EQs such as Renaissance Equalizer or F6.

7. EQ Emulations

Earlier in the article, we discussed a number of classic analog hardware EQs and highlighted some of their strengths and weaknesses. In almost all of them, you’ll find their tone and character on their strengths list, and cost or practicality on their weaknesses list.

Best EQ emulation plugins to try in your next mix

Thanks to modern modeling technology, we’re able to combine the sonic properties of vintage analog hardware with the practicalities and cost-effectiveness of digital software. We’ve already mentioned some plugin recreations of classic equalizers, but there are plenty more on our website including the API 550 and Kramer HLS Channel.

8. Dynamic EQ

While most equalizers are static in that the processing remains the same no matter the level or frequency of the input signal, there might be circumstances where you want to process the signal according to the contents of the input. In these cases, a dynamic EQ is the answer.

Waves F6 dynamic EQ plugin

Using a dynamic EQ like Waves F6, you can apply traditional parametric equalization as with any other EQ. By using the Threshold, Range, Attack and Release controls, you can also apply that equalization dynamically, and on a per-band basis too. The internal sidechain signal is useful for attenuating particularly loud frequencies or instruments, or the external sidechain is an effective method of creating frequency separation in your mix.

9. Automatic EQ

Just when you thought equalization technology couldn’t get any more advanced, automatic EQ tools join the lineup. Automatic EQs aren’t necessarily a replacement for any of the other types of EQ covered here, but can instead be used alongside them to add further tonal enhancements to your mix.

Waves Online Mastering employs automatic EQ as one part of its processing, and also gives you some control of the overall tone of your master with the Depth and Presence controls. Silk Vocal is a smart EQ and dynamics processor that applies dynamic EQ to your signal according to the frequency content of your vocals. While Silk Vocal doesn’t operate the same way as a traditional EQ, the Low, Mid and High bands give you some level of control over the processing being applied.

Waves Silk Vocal plugin

Which EQ is right for you? As you can see from the options we’ve laid out here, there’s rarely one EQ that can do it all, but having a few types of EQ in your plugin folder means you’ll have access to the necessary tools for any task you’ll ever face while mixing and mastering.

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