How did the legendary engineers of the past use dynamics processors?
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 my 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 topics: how the process of recording worked and how and why the technologies that were so important to that process were utilized. Plus, we will also discuss the products that engineers used to record the great popular music that we have come to love and to cherish. 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 dynamics processors. If there is a singular component that is important to understand about this particular part of the process of recording music, it is how the great engineers of the past used compression.
Understanding Dynamics Processing
Compressors, gates and limiters are all dynamics processors and each functions in a similar manner. In fact, compression is actually quite easy to understand, but for those who have never worked in the world of professional audio, it is not a timing process (though timing is a component of it— more on that in a moment), it is a dynamic one. In other words, dynamics processors such as compressors, gates and limiters impact the amplitude or volume of a signal. Compression is used to lower the loud areas of a signal and to raise the quiet areas of a signal. It simply takes the quiet areas and makes them louder and the loud areas and makes them softer. Limiters are simply brickwall compressors. A limiter keeps high volume signals from becoming too dangerous for either your speakers or monitoring systems. Most of the time, we can think of limiters as being the final step in a chain, for example before a signal is broadcast. Gates work in the opposite direction— keeping quiet signals from being heard until they reach a certain level of loudness. Can compression be used as an effect? Compression can be used as an effect or it can be a process. Originally, compressors were simply referred to as broadcast, or peak limiters or even as leveling amplifiers. The concept was that these processing units allowed for the ability to control excessive volumes in a manner that sounded both smooth and natural. Early limiters by 1958, therefore, found their way into mastering houses, such as the Fairchild 660 and later, the 670 (which was a stereo version of the 660) where these units were used to prevent dangerous volumes from becoming a problem as discs were being cut to make early vinyl masters for producing records. Later, in 1963, compressors would be used for peak leveling on vocal and instrument tracks as the process of multitrack recording evolved with such units as the Teletronix LA-2A. In 1967, with the development of such units as the UREI 1176, leveling amplifiers became much more capable of shaping signals through the process of peak limiting. By 1969, with the introduction of such units as the 2254 by Rupert Neve, the modern compressor as we think of these units today with multiple shaping functions (input, threshold, ratio, attack, release and make-up gain) started making their appearance in the early 1970s in the great Neve consoles of the era— a trend that has continued in magnificent analog consoles which continue to be developed by such famed brands as AMS-Neve, API, SSL and even Audient has introduced a buss compressor into both their flagship and smaller-format consoles. In the late 1970s and early 1980s, rack-mount compressor units, and by the 1990s, 500-series module units started becoming popular with both studios and professional engineers who carried them, at the time, from studio to studio in their own gear racks. Today, dynamics processors still come in both rack-mount and 500-series module units, but the use of software plugins which feature emulations of many of the greatest hardware units of all-time are incredibly popular and much less expensive than their hardware counterparts.
Other Dynamics Processors
How do compressors work?
Perhaps, next to microphone preamps, compressors have become the most indispensable tool for professional recording studio engineers. Compressors allow for signals to be recorded in a manner that is smooth and natural, while preserving the dynamics of a performance in such a way that it allows for more volume to be captured in a track. In fact, most of the people who listen to music, but have never seen a recording studio before know what equalization is to a large extent, but very few people (even some engineers, do not have a full grasp of the use of compression). It’s truly the magic that occurs in a music recording environment, at least from the standpoint of having a special piece of gear that can be found in no other audio environment. For just a moment, imagine a singer who opens a song with a soft whisper, but by the time they reach the chorus of a song, they are virtually screaming into the microphone. Each one of us has heard a song just like the one that I just described— maybe it is our favorite song of all-time. But, you might ask, how does the singer sound so smooth to my ears while performing a song that is so dynamic that it can move so quickly from a whisper to a thunderous chorus? The answer is compression. What you are listening to is a compressor at work. Where else in a song are you hearing compression? The answer should not be too surprising. You are hearing it everywhere— it’s on every track. From the thunderous drums, to the softest acoustic guitar tracks, you are listening to compression at work in just about every single song in the history of popular music from the late 1950s moving forward to today. Instruments that are commonly compressed in a song include vocals, bass guitar, electric guitar and the drums. Engineers commonly compress these tracks while recording (though it is often subtle), and then add more compression during the mixing process where in a digital audio workstation or at an analog console they can compress, for example each of the drum tracks in a drum kit individually and then also compress the entire drum kit as a unit— this is referred to as compressing a submix (or a smaller group of instruments in a mix-- nowadays, engineers often refer to these as stems). Plus, to pull the tracks in a song together and to provide more punch for the dynamics of it— all of the tracks are often compressed and then quite often a limiter is placed on top of the mix of the song that you are hearing. If compression is used so often and it is so important to the development of a song in popular music, how does a typical unit work?
If you are looking at a typical compressor, you will find the following controls and functions. The following will represent what each control does and the function that each will provide for you as an engineer. It should be noted that most, but not every compressor will have the same functions. The first common control is referred to as an input, which is the function that allows you to be able to control the amount of a signal that is coming into the compressor. The next four functions are crucial to understand because each one of them will spell out how the unit will function as a compressor. These crucial functions are ratio, threshold, attack and release. The ratio function simply allows you to set the level of compression usually based on a set of ratios— 2:1,3:1,4:1 or 10:1 are often seen. What do these represent? A ratio of 3:1 means that for every 3 decibels of a signal, only 1 is allowed to pass through. This is a common ratio for compressing vocals, so it can even give a highly dynamic performance a sense of smoothness. The threshold function lets you set when the compression process begins— common settings include: 0, -10, -20, -30 or even -50. This is the decibel level at which the process of compression begins. The next two functions work in tandem— attack and release. The attack function allows you to select how quickly you want the process of compression to begin working. The release function simply does the opposite, it allows you to select when you want to stop or halt the process of compression. The other controls you may have on a compressor have to do with what you hear coming out of the unit— make-up gain and or a dry/wet function. The make-up gain allows you to be able to boost the volume of the compressed signal. The dry/wet signal allows you to select the amount of a signal that has been compressed to be heard— less or more, in other words you can hear no compression at all (or bypass it), or just the compression. Also, most compressors will allow you to monitor either the signal coming into the unit or how much of the signal is being reduced by the process of compression.
Also, there are different types of compressors and each type does work differently. The most common types are VCA, diode-bridge, FET and optical units, though there are certainly others. Without getting into electrical engineering speak, let’s consider what each of these three common types of compressor are used for in either the recording and or mixing process. Each type of compressor is named after the element within it that allows for the process of compression to occur. To put it simply, each element within each compressor will allow the unit to function in a different manner— particularly in how each will react to a source. Both VCA and diode bridge units can react either quickly or slowly to a source and are extremely flexible, plus, tend to impart a character to the sound coming out of them. For example, an API (VCA) compressor will not sound like a Neve (diode-bridge) compressor. The VCA tends to be punchy and authoritative, while the diode-bridge tends to be very rich in its character. Optical units often have tube elements in their circuitry and are therefore very warm and slower reacting to a source. So, if you are thinking along these lines— a VCA compressor is often great on extremely dynamic sources, like drum tracks, for example, while diode-bridge compressors tend to shine on groups of material or even overall mixes. FET compressors tend to react very quickly to source material and though they may have the smooth appearance of an opto compressor, these units can be used to crush source material— making them great for taming extremely loud sources such as electric guitars. Opto compressors, however, tend to be perfect at applying warmth and character to slower developing but dynamic sources such as vocals, bass guitars or even acoustic instruments (depending on the nature of the song). In other words, the legendary engineers of the past and the great engineers of today tend to select compressor units based on both the sources and the nature of the songs that they are working on.
Pictured above is the software plugin compressor that I was using to work on a music file in GarageBand.
How do limiters work?
It’s interesting to note that compressors came from limiters originally. But, in today’s world of professional music recording, the vast majority of compressors can still function as limiters, but most of the devices that are classified as limiters cannot function as compressors. As was noted above, compressors have the ability to smoothen signals, allow for the boosting of the volume of your tracks in a safe manner for your equipment and preserve the dynamics of a performance. Limiters are much more one-dimensional. In fact, in today’s market, limiters are almost exclusively used for speaker or monitor protection from signal overload. Very few pure limiters are used in the world of professional music recording, but they are still used in both broadcast and live performance applications. While most limiters prior to the 1980s and the age of digital were also analog units, there are very few pure analog limiters available today. The vast majority of the limiters that you will find today are digital units, or come as a software plugin. Since limiters are essentially brickwall compressors, these units work in exactly the same manner. Though limiters are not usually used often in music recording or mixing, there are units which are used in mastering which is the final process of a recording prior to it being released to the public, but even these units function more like a traditional compressor and are used in a similar manner.
Pictured above is the peak limiter that I was using to work on a music file in GarageBand.
Pictured above is the noise gate that I was using to work on a music file in GarageBand.
How do gates work?
Gates are the opposite of a compressor, in that the job of a gate is to close off undesirable signals and to open and allow desirable signals to pass through. Most of the time, a gate is also referred to as a noise gate and this is because the term describes exactly why these devices are used. With the advent of digital audio workstations and software plugins, very few manufacturers now make noise gates that can be purchased in the professional audio realm. It is also worth noting that sometimes gates are referred to as expanders— primarily because they do work in the opposite direction of a compressor. Though I will describe uses for a noise gate in another section of this article, it should be noted that the use of gates has diminished over time quite a bit. Gates have to be triggered to work properly to seal off a sound source. A gate can be triggered by volume or by a prescribed frequency. A gate could be used for example, to diminish background noise that a microphone might pick up and then when the source is played, it could be triggered to open so that you cleanly hear the source without the extraneous noise. Most digital audio workstation software programs contain gates as a part of their package of plugins. A gate might be useful for example, if you have a speaker at a podium and you wish to eliminate noise from the microphone until the person steps up to deliver their speech. The vast majority of the time, gates are used in the mixing process to eliminate sound sources bleeding into the pick-up area of a microphone— for example, where a number of microphones are placed together in a small area, such as a drum kit. Eliminating this undesirable noise can lead to cleaner signals to mix. Gates can also be used to expand certain sounds or even frequency ranges, so this enables them to also function as an effect, too. In my opinion, it takes a master engineer to use gates during the process of recording, because you do not want to make a mistake that could cost you precious frequencies (particularly in the low-end) if you record using them in a problematic manner. Gates remain important in the world of professional music recording, and the ability to use them wisely may be one of the most overlooked skills in the engineering profession. Of course, as has been mentioned before, excellent microphone technique can be a factor in eliminating the need for the use of gates or other dynamics processors.
Are there other types of dynamics processors?
There are other types of dynamics processors— de-essers and multi-band compressors or limiters. Plus, there are digital compressors, as well. A de-esser is a specialized processor which is normally used just for the task of removing the sibliance from a person’s voice. A heightened sense of awareness should be taken when using a de-esser, in that, you do want to remove the annoying sibilance, (the over-pronunciation, or anunciation of the “s” syllable) but you do not want to remove the other perhaps very valuable components of a vocal. Rather than use a de-esser, it is often better to select a different vocal microphone, or to use a filter on the microphone to negate the problem. In other words, a de-esser can be thought of as a processor of last resort to use. A multiband compressor or limiter allows you to compress or even limit a band of band of frequencies for a signal or a group of signals. This can be very useful if you are working with a submix of drum tracks or an entire mix prior to printing a master for a song. Digital compressors most often come in the form of software plugins.
Pictured above is a de-esser that I was using to work on a music file in GarageBand.
Pictured above is the multiband compressor that I was using to work on a music file in GarageBand.
How did the legendary engineers of the past use dynamics processors?
If one were to create a list of each of the processors in the racks of the gear of the greatest recording studios in the world, those racks would have more dynamics processors in them than any other type. Compression is fundamental to shaping the sounds of vocals, drums, guitars and mixes, as a whole. Perhaps no other type of processor is more utilized by engineers than compressors. That said, most of the great engineers of the past used compression sparingly. In other words, it was used to smoothen tracks and to preserve the dynamics of a performance. If you have ever listened to the screaming, but poignant vocals of the brilliant Aerosmith frontman, Steven Tyler, and wondered why they appear to be so smooth, but yet so dynamic in their amazing songs, it is the compression applied by truly legendary engineers such as Jack Douglas, Jay Messina, Bob Rock, Mike Fraser and David Thoener and others to their music over the years. The bone crushing electric guitars that you hear in rock music, the smooth electric guitars that you hear in blues, jazz and even the jangle of electric guitars in country music are all made possible through the use of compression. Take the electric guitar tracks of the brilliant Carlos Santana— what you are hearing is subtle compression to make his dynamic performances sound so smooth and so natural (no puns intended).
However, it is the ability of the great engineers of the past to use compressors and gates on the drums which changed the nature of popular music— both how it sounded, and too, its mass appeal. Beginning in the early 1980s and into the late-1990s with legendary engineers such as Jay Messina, David Thoener, Ron Nevison, Bob Clearmountain, Bill Wittman, Bruce Swedien, Michael Verdick, David Leonard, Kevin Beamish, Hugh Padgham, Chris Kimsey, Jim Barbour, Bob Rock, Bill Schnee, Steve Lillywhite, Shelly Yakus, Frank Filipetti, David Devour, Calvin Harris, Tchad Blake, Mick Guzuaski, Chris Porter, Donn Landee, Tom Lord-Algae, Mike Shipley, Phil Castellano, Bill Bottrell, Mike Clink, Don Gehman, Chuck Ainlay, John Guess, Steve Marcantonio and Neil Dorfsman, drum tracks took center stage as did the genres of rock, pop and eventually country music. Each of these engineers were true masters of the trade and it was their work that would dominate the charts in each of those three respective genres from 1980-1995 and even beyond. If you want to hear compression at its best, listen to the music of this era. It was the era in which drum tracks had their greatest variety— from gated reverbs on the snares, to the thunderous toms and the kick drums, which for the first time could emulate a human heartbeat in a ballad. Each of these tracks certainly were well-recorded, and there was use of equalization, reverb and other processesing, but in the 1980s and 1990s, the use of compression brought the drums in pop, rock and at the end of the period, country music to life and drove these genres into the popular music of the future. Compression was not just at the heart of the thunderous drums of the period from 1980-1995, so was the use of compression to give us the dynamic hits of the period. (It is also important to note that sampling became available during this period and that a number of the drum tracks that you were able to hear on the radio were not truly recorded signals in some cases, but digital samples of drum sounds that were triggered to replace the real drum sounds.)
The popular music that lit up the charts from 1980-2000 in rock, pop and country featured compression, not just on most of the instrument and vocal tracks, but also in both the stereo mix and in the form of submixes, as well. (It should be noted that these are now referred to as stems.) To explain, a typical submix would work like this— take all of the drum tracks and using your console, you could route just those tracks to a stereo compressor (using either your aux sends or the bussing matrix) and then return those tracks in stereo to your console on two open channels. It not only served to make drums tracks larger than life, but also smoother and richer. With the advent of stereo compressors that could be used to add both punch and glue to a final mix before printing it to a master format (tape or DAT) at the time, you could also add additional compression and usually, a limiter, as well. This process served to give the music of the period its authoritative punch, while still preserving the dynamics of the brilliant performances of the time. Using compression requires skill and great listening and attention to detail. For example, it is quite easy to give a vocalist a lisp if you misuse the process of compression or de-essing. An inattentive engineer can misuse noise gates and lose critical elements of the performance of a drummer. The inability to use a limiter properly can even result in the damage of your monitoring system. But, the use of dynamics processing in the hands of a legendary engineer can also make a song into a classic hit and preserve the best elements of a performance for the fans of popular music to be able to listen to and to enjoy for many years to come.
What are some of the great dynamics processors of the past which are still used to record the great popular music of today?
The following represents some of the great dynamics processors which were used by the legendary engineers of the past that can still be found in recording studios today. You can use these links to find out more about each of these amazing dynamics processors and the amazing companies, too, which make them.
Pictured above is one of my favorite software plugins, the Focusrite Red 3 compressor unit.