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How did the legendary engineers of the past use it? 



At The Recording Session Vault, it is an important component of our mission to promote an understanding through education about how the great music of the past was created. While part of our mission is to write biographies of the people behind the music, feature articles about the great studios, and also to examine the technologies and to spotlight the companies that created them that have been so crucial to the development of popular music, it is also important to understand how the process of creating music actually worked, as well. With this educational series, we will explore the following two topics: how the process of recording worked and how and why the technologies that were so important to that process were utilized. Without further ado, the first series of articles will focus on the types of processors that were used to record, mix and master the great music of the past. There are three types of processors: spectral processors (equalization units); timing processors (reverb and delay units) and amplitude (or dynamics) processors (compressors, gates and limiters). This article will discuss spectral processing, or as we more commonly refer to it— equalization. Most of us have heard of equalization, so when discussing the world of professional music recording, it is an easier and more familiar place for us to begin this series of articles.

Understanding Equalization


Equalizers or EQs as they are commonly called are spectral processors. In other words, it is a processor which deals with the range of frequencies that make up the sounds of the music that you are listening to. Most people who have excellent hearing, can hear frequencies between 20Hz and 20KHz (or, 20,000Hz). Some animals, like dogs and cats can hear more frequencies with more accuracy than we can as human beings. As we all know from our science classes, sound is made up of waves— well, each wave is a frequency. To put it simply, the shorter the wave the higher the frequency, and conversely, the longer the wave, the lower the frequency. An example of how this plays out in our everyday reality is when you are listening to a thunderstorm and the roll of a powerful thunderclap seems to shake your house. It shakes your house because lower frequency waves are longer and therefore more powerful— but, though they pack a punch, they are also less defined. If you are sitting in a theater, for example, that has excellent acoustics, it is the mid-range (500Hz to 10KHz) frequencies that give you the definition of what you are hearing transpire on the stage.These frequencies allow us to understand the speakers and what they may or may not be trying to convey in their performance. Higher frequencies (10KHz to 20KHz) clarify the definition of what we are hearing, enabling us to better understand the sense of emotion that we might not otherwise gain from listening to a performance. So, in effect, what equalization allows us to do, as engineers, is to be able to tailor those frequencies— to add or to take away punch, definition or clarity to or from an instrument or a voice.

How does it work?


There are two different types of equalization units, and filters that are typically applied by engineers to shape and sculpt the sounds of an instrument or a voice. In this section, we will examine the following types of equalization units and filters, plus, I will give you examples of each type of unit that have been used extensively by the great engineers of the past. And, also look in our articles section of the website for the history of the development and use of these units. Plus, if you are interested in one of these units, I will provide a link for each one of these amazing pieces of gear for you to check out, as well. Keep in mind that most of the equalization units that have been used by the great engineers of the past, often include elements from each of the categories listed below for discussion. For example, a unit may contain parametric equalization functionality, but also provide both Low-Pass and High-Pass Filters, too. The first great equalization units that were developed by the early 1960s, such as the Pultec EQP-1A, from Pulse Techniques were referred to as program equalization units and could either boost or cut a wide range of frequencies in either the low end of the spectrum, or the high end of it and used vacuum tube-based technology. Popular program units include those made by Pulse Techniques and Manley Labs. Many of the great equalization units that were used in the past feature both vacuum tube and solid state technologies and actually came from some of the fabulous early large-format consoles that were developed in the early to mid-1970s.


  • Parametric Equalization Units

  • Graphic Equalization Units

  • High-Pass Filters

  • Low-Pass Filters

  • Notch Filters

Parametric EQ.png

Pictured above is the parametric equalizer that I was using to work on a music file in GarageBand.  

Parametric Equalization Units


Perhaps the most common type of equalization unit used by the great engineers of the past were parametric equalization units. With a parametric equalization unit, an engineer could select a specific frequency within a range of frequencies (referred to as a band of frequencies) and could either boost or cut that frequency. At first, most parametric equalization units dealt with two bands of frequencies— both high and low frequencies that were divided into two distinct ranges. By the mid-1970s, three-band equalization units had become much more common and featured of course, the ability to cut or boost frequencies in the low, mid, or high-frequency bands. These units used knobs with detents to cut or boost frequencies— one knob would select a frequency, while another knob would either boost or cut it. There are also, of course, four-band parametric equalization units which split the extremely large range of frequencies in the mid-range into two separate bands (an upper and a lower-mid-range band). Like most processing units in the world of music recording, these units were very easy to use, although some of them are quite small in their footprint and some today can be found as 500-series units. Popular parametric units include those made by AMS Neve, Trident, SSL, API, Focusrite and GML. Most of these units also include Hi-Pass and Low-Pass Filters, as well, in their functionality. 

Graphic Equalization Units


Though not as common, but perhaps even easier to use, are graphic equalization units. These units would contain a wide spectrum of frequencies from the low-frequency to the high-frequency end of the spectrum and an engineer would use sliders to select a specific frequency and then slide it down to cut a frequency or up to boost it. They do not offer the wide range of flexibility that the parametric units do, plus, they do not contain High or Low-Pass filters. However, for someone who is stepping into engineering for the very first time, these units do offer two advantages— ease of use and quite often, they are also inexpensive to purchase. Popular graphic equalization units have been made by both API and DBX.

Graphic EQ.png

Pictured above is the graphic equalizer that I was using to work on a music file in GarageBand.

Filters EQ.png

Pictured above are the equalization filters that I was using to work on a music file in GarageBand.

High-Pass Filters


A high-pass filter is exactly what it says it is— a filter that lets only frequencies above a certain range in the frequency spectrum pass through to be heard. In other words, let’s say that you apply a high-pass filter that begins at 60Hz, what this means is that you will hear no frequencies below 60Hz, but you will hear everything above it. While I rarely saw high or low-pass filters applied in a recording session, or on a mix for that matter, they can be useful for getting rid of unwanted noises. Most of the units from AMS Neve, Trident, SSL, API and Focusrite will contain high and low-pass filters.


Low-Pass Filters


Conversely, a low-pass filter is also exactly what it says that it is— a filter that lets only certain frequencies below a certain range in the frequency spectrum pass through to be heard. If you apply a low-pass filter at 16KHz, then you will hear nothing above 16KHz, but you will hear all of the frequencies below it. Again, I rarely saw an engineer while tracking or mixing engage or use either a high or low-pass filter, but they are easy to use and at times, can be useful. But, keep in mind, they are usually used to remove unwanted noises from program material, so if you find yourself using them, maybe re-position your microphone or change the recording environment, so that you do not have to use them. Most of the units from AMS Neve, Trident, SSL, API and Focusrite will contain high and low-pass filters.

Notch Filters


A notch filter is used to remove a singular troublesome frequency. I have never seen an engineer use one during an actual recording session— either while tracking, recording overdubs or mixing. A notch filter works like this— you select a frequency, let’s say 60Hz to get rid of the hum from a device, for example. A notch filter would help you get rid of the hum, however, it will also get rid of every great sound in the spectrum that may be surrounding the troublesome frequency, too. If you have to use a notch filter, you should consider getting rid of the source of the troublesome noise first and then re-record the program material rather than use one. Most digital audio workstations contain a software plugin that can be easily used as a notch filter. 

How was equalization used by the great engineers of the past?


During tracking, or the recording of an album, each of the great engineers that I worked with used equalization sparingly, and almost never recorded it to tape or into a digital audio workstation. Once you record a signal that is problematic, you have it as a problem that will always have to be fixed. Never use equalization to fix a problem. If you have a problem— eliminate it before the recording process. If you find that you are trying to use equalization a lot during the process of recording— consider that you may need to have a better room for recording the material, or that maybe you need to consider the use of a different microphone (or microphone technique) before ever considering the use of equalization. As a tool, the great engineers that I had the fortune of working with used equalization to cut subtle problems from their program material. It was extremely rare for me to see an engineer add a lot of equalization to any track for any reason at any point in the recording process. However, I have seen great engineers use equalization as a tool to create an effect during the mixing process. The best examples of the great engineers of the past using equalization as an effect was in the creation of drum sounds— shaping a kick drum to sound like a heartbeat, giving a snare drum more crack to it, or using it to give toms more punch. Equalization, therefore— can be an excellent engineering tool, especially during the mixing process to sculpt or shape instrumental tracks— but, it was not extensively used in the process of recording them. In other words, having solid or full tracks that were well recorded by the tracking engineer, allowed the mixing engineer to use equalization as more of a tool for creating effects that were desired by the artist and the producer to enhance the quality of the program material. 


I love this quote from the legendary recording studio engineer, Shelly Yakus, who has both mentored so many great engineers of the past and who has recorded and or mixed some of the greatest songs in the history of popular music (The Band, John Lennon, U2, Aretha Franklin, Madonna, Bob Seger, Don Henley, Belinda Carlisle, Stevie Nicks and Tom Petty and the Heartbreakers— and so, many other fabulous artists through his legendary career). He once noted,“Eliminate the things you know are wrong and you will be left with what is right.” Though this quote could well be applied to almost any component of the recording process, I find it extremely useful to think about when considering how the brilliant engineers of the past used the process of equalization, in particular. 


What are some of the great equalization units from the past that are still being used to record great popular music today?


The following represents some of the great equalization units used by the legendary engineers of the past. You can use these links to find out more about each of these amazing equalization units and the great companies, too, which make them.


Pulse TechniquesEQP-1A and MEQ-5 Equalization Units

Manley LabsEnhanced Pultec and Massive Passive Equalization Units

AMS Neve1073® and 1081 Equalization Units

API550A, 550B and 560 Equalization Units

Focusrite (ISA 215 and Red 2— neither of which are still made by the company. However, I do love the Focusrite Red 2 software plugin.

GML 8200 Equalization Unit

Trident— A-Range (Rack-mountable and 500-Series) and 80B Equalization Units

DBX1215, 1231 and 530 Equalization Units

Note: The 1073® is a registered trademark of AMS Neve Limited.

RED 2- EQ.png

Pictured above is one of my favorite software plugins, the Focusrite Red 2 equalization unit. 

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