How to Mix and Master with EQ – 10 Equalizer Modes – Part Eight - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Eight – High Cut and Low Cut EQ

In my last Post I mentioned that some beginners get confused by terminology when they come across settings like high and low pass filters and EQ's. It is logical, since it is a strange naming of things, but once we understand that pass quite literally means letting a range of the spectrum pass through, we can start to see the reason for using these settings. So, why would there be a different EQ mode for high and low Cut EQ's? Well, technically we could get by with just using one or the other, since they are often synonymous with each other. A high cut EQ can work essentially the same as a low pass EQ and the same with a low cut and a high pass. A high cut EQ will remove the audio signal above the target setting, and a low cut EQ will remove the audio below the target setting. One could argue that this seems more logical than a “pass” EQ. Not everyone may catch on to the logic of a pass filter as soon as the obvious terminology of a cut EQ. But, does this mean that they are essentially the same thing, and if so, why would they be called one instead of the other? The truth is that one EQ mode can “pass” for another (pun definitely intended). Cutting lows below a certain point is the same as allowing all audio above that point to pass. But, the factors that surround pass and cut filters can be different. Typically, a pass filter is a preset shape, and only the pass Frequency may be changed. With a cut EQ, it is possible that the same Frequencies and even same EQ shapes may be chosen as the pass filter. But, sometimes with cut, we may have a different array of frequencies and we may also have the ability to adjust the Gain, depending on the EQ.

The methodology of the cut Frequency can vary, from the amount of decibels per octave that are cut to the type of filtering process used to achieve the goal. As we will see when looking at Shelf EQ's, the selected Frequency is not the only factor determining a pass or cut filter. The shape of the filter tends to serve a reason that some designs call the setting a cut or pass filter.

Although it is true that it can designate the same thing, there is more variation involved in the potential settings of a cut EQ slope and shape, depth, and options for Gain control. Cut EQ can designate that it is offering the user the opportunity to eliminate a Shelf-type reduction of a wide range of Frequencies above or below the threshold, but it also leaves the options open to define how deep the cut is, and whether it is a soft taper or a strong brickwall cut-off. With a pass EQ, the only factor that the user is to consider is the Frequency that serves a cut-off point, and everything beyond that threshold is to be completely gone as best served by the design. So, in its purest form, the cut and pass filters are very similar, but cut tends to share characteristics with the Shelf EQ and pass EQ, where there is some room for flexibility in shape, Gain, slope, and depth, but the bottom line is the goal to cut Frequencies to a deep setting, with an understanding that some designs allow for more flexibility, and still others may have a set cut-off filter and a separate Shelf option.

How to Mix and Master with EQ – 10 Equalizer Modes – Part Eight - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Eight – High Cut and Low Cut EQ

In my last Post I mentioned that some beginners get confused by terminology when they come across settings like high and low pass filters and EQ's. It is logical, since it is a strange naming of things, but once we understand that pass quite literally means letting a range of the spectrum pass through, we can start to see the reason for using these settings. So, why would there be a different EQ mode for high and low Cut EQ's? Well, technically we could get by with just using one or the other, since they are often synonymous with each other. A high cut EQ can work essentially the same as a low pass EQ and the same with a low cut and a high pass. A high cut EQ will remove the audio signal above the target setting, and a low cut EQ will remove the audio below the target setting. One could argue that this seems more logical than a “pass” EQ. Not everyone may catch on to the logic of a pass filter as soon as the obvious terminology of a cut EQ. But, does this mean that they are essentially the same thing, and if so, why would they be called one instead of the other?
The truth is that one EQ mode can “pass” for another (pun definitely intended). Cutting lows below a certain point is the same as allowing all audio above that point to pass. But, the factors that surround pass and cut filters can be different. Typically, a pass filter is a preset shape, and only the pass Frequency may be changed. With a cut EQ, it is possible that the same Frequencies and even same EQ shapes may be chosen as the pass filter. But, sometimes with cut, we may have a different array of frequencies and we may also have the ability to adjust the Gain, depending on the EQ.

The methodology of the cut Frequency can vary, from the amount of decibels per octave that are cut to the type of filtering process used to achieve the goal. As we will see when looking at Shelf EQ's, the selected Frequency is not the only factor determining a pass or cut filter. The shape of the filter tends to serve a reason that some designs call the setting a cut or pass filter. Although it is true that it can designate the same thing, there is more variation involved in the potential settings of a cut EQ slope and shape, depth, and options for Gain control. Cut EQ can designate that it is offering the user the opportunity to eliminate a Shelf-type reduction of a wide range of Frequencies above or below the threshold, but it also leaves the options open to define how deep the cut is, and whether it is a soft taper or a strong brickwall cut-off. With a pass EQ, the only factor that the user is to consider is the Frequency that serves a cut-off point, and everything beyond that threshold is to be completely gone as best served by the design. So, in its purest form, the cut and pass filters are very similar, but cut tends to share characteristics with the Shelf EQ and pass EQ, where there is some room for flexibility in shape, Gain, slope, and depth, but the bottom line is the goal to cut Frequencies to a deep setting, with an understanding that some designs allow for more flexibility, and still others may have a set cut-off filter and a separate Shelf option.

How to Mix and Master with EQ – 10 Equalizer Modes – Part Seven - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Seven – High Pass and Low Pass EQ

Many people start recording their own music and learning the basics in mixing because they have an idea for a song, and others get involved because they have played an instrument for some time and want to record themselves in the context of a song with other instruments. Still others join a band, and once they sound decent they want to document their efforts, and some like to sing and write lyrics and try their hand at making their own tunes, either with MIDI or samples. Whatever road that gets them there, if we are talking about the self-taught beginning recordist, one thing that typically mystifies the early learner is the high pass/low pass filter or Equalizer.

They might have an easy grasp on what an Equalizer is, and what makes for different Frequencies, Spectrum, Gain, among other vocabulary. But, high and low pass may not automatically make sense. Especially if they learn about “pass” at the same time as they learn about “cut” they may be even more thrown for an answer.
The truly simple explanation for high and low pass EQ is to take it for face value. A high pass Equalizer allows everything above a certain Frequency to “pass,” meaning that all of the signal above that setting will remain and will not be removed. For example, a high pass EQ set to 100Hz means that everything from 101Hz and up will remain. This also means that everything below 100Hz will be removed.

The same concept applies to low pass EQ. In this case, the low signal spectrum is going to be allowed to pass. So, in the same situation, if a low pass EQ was set to 100Hz, we would no longer see any audio above 101Hz, thus we would only hear low Frequencies.

The “pass” EQ is designed to isolate only what is needed and to remove everything that is causing trouble at a fixed point. Because it can make a very strong statement and a very obvious change to the signal, the “pass” point is usually not set, but is usually given several fixed Frequency options. These are usually chosen at points that are known to have typical audio issues. One point might be set to remove low end rumble, and another may be set to reduce grounding noise or audio interference hum. Another setting may be set below our usual hearing level just to clear any noise that is not intended just in case it is there. Higher Frequency high pass filters, like those above 80Hz, sometimes as high as 150Hz or even 200Hz help to clarify a signal that does not rely heavily on low Frequency content. This could be anything from a mid-to-upper piano part or vocal, a guitar or cymbal, and numerous other items. A pass filter can be used on an effect channel like reverb or time-based effects like delay or chorus or flange, to separate out residual effects from their original signal, making the dimension of a song more intricate.

The low pass EQ can be used to get rid of buzz or hum sitting on top of a clean bass guitar line, or change a slap and tap string artifact to sound more like a purposeful tonal performance. High pass can be used to remove all upper Frequencies and hiss and noise that is recorded as part of a low Frequency signal that is not desired. It could also be used on effect tracks to change the way an effect sounds on content that otherwise has a lot of high Frequencies, but it can also be used at the highest Frequency option supplied on a low pass filter to create a special effect from a track that normally has more spectrum in the sound, like making a voice sound like it is coming from a telephone or an older recording device.

It is very rare that a pass EQ will be completely variable, meaning that it is usually provided with a few fixed Frequency options that make for a usable utility for removing trouble above or below a certain point, but this is usually not given complete flexibility. It is also not as common for there to be only a single fixed pass Frequency, since there can be different spectral issues that come up on a regular enough basis that call for using pass filtering options.

How to Mix and Master with EQ – 10 Equalizer Modes – Part Six - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Six – Fixed “Q” width versus Variable “Q” width EQ

What EQ Mode is right for the job? Should you use an Equalizer that has fixed Frequency positions or one that is freely selectable? Should you use an EQ that can switch between various types of filters, or has a limited, but well chosen, set of precise settings? Do you want to work within a system of choices that always works well but also helps you to place your signature on your sound, or do you want complete flexibility to make independent choices at every turn, with the potential that many different types of music have an excellent result with an indistinguishable trademark in your artistic choices?

There is no single correct answer to these questions. It is just as justifiable to mix and master with an artistic touch that is complimentary and well-suited to each mix that also gives a nod to your personal style as it is to work with absolute precision and surgical care, letting nothing but the artist's best efforts shine through, never showing favor to one adjustment over another from song to song, album to album. These choices are central to the equipment that will serve us best. Equalizers that have a Fixed “Q” width are not necessarily as limiting to a person's options as one might think. A Fixed “Q” Equalizer may also have Fixed Frequencies, or the Frequencies may be fully adjustable from one range to another. There are no set rules from one EQ type to the next as to whether they must have an adjustable “Q” width. Not only does it make a difference if the “Q” can be adjusted or not, but for a Fixed EQ, we will make decisions based on just how wide the “Q” is set. Typically, “Q” has little significance when an EQ has multiple settings in its high and low Shelf settings. A Shelf setting typically will reach all the way to the end of the Spectrum.

Normally, when an EQ has a Fixed “Q” width, the “Q” is wide enough to affect the full width between one point and the next, with a smooth curve depth, meaning that the top of the mountain is rounded off to keep Gain adjustments smooth. At its deepest or steepest Gain, it will narrow steadily but still remain a smoother transition than if it were adjustable to a narrower “Q”. In very rare exceptions, an EQ may be marked at a wider “Q” than others.

An example is the NSEQ-2, which has a very wide interpretation of “Q” width. Even though it is marked at standard options, it is extremely smooth, and wide. Even at its narrowest setting, which is incredibly useful for mixing and mastering, it is not as sharp and narrow as an EQ like the Sontec, or even more the Amek 9098. We tend to think of a Variable “Q” as being the most flexible, and in most ways this is true. If the Frequency and the “Q” width are both Variable, then we can assume that any Frequency within the marked range can be broadly the center point that is adjusted, or can be sharply targeted for pinpoint removal. With Variable “Q” width, you have a bit more to learn about your EQ and its range of personality.

You may not find yourself using the exact same settings as often and for as many similar routines, so I always recommend taking time to learn the sound of your equipment, whether real or virtual. Load up sounds, songs, or tracks as “test” tracks that you are familiar with. Before you use an EQ that has tons of freely selectable positions, test it out with a lot of care. How does the sound change from wider “Q” to narrow “Q”? Does it sounds very similar or does it go from very smooth to extremely precise. Some EQ's increase a great deal in Gain the more narrow the “Q” selected. You may be used to using something at a medium “Q” at 5dB for boosting vocals or scooping guitars, and then you run into a place where there is unwanted resonance on a similar

Frequency; not an artistic decision but a corrective issue that needs attention. That 5dB is likely to narrow at the start of the slope in a similar fashion to the medium “Q” you are used to, but as it often sharpens to a point at higher Gain settings, it reaches much more signal increase or decrease, and you may be removing more than anticipated. It is not as easy to design the perfect Variable “Q” width EQ as one might think. The sonic results of one exact shape to the next is amazingly different. Narrow “Q” is good to have in some form, since it is hard to reduce serious trouble areas without a good sharp point that goes into deep Gain. This is not an easy task in analog or digital form. I can speak to this, as I was personally not satisfied with any result, analog or other, for extreme surgical EQ, so I set out to design my own. I created my Mastering Suite Equalizer that uses my own process that I created specifically for addressing surgical EQ for mastering music at 44.1kHz. The Amek 9098 is an extremely close second to having some of the most incredible EQ shapes, including very sharp narrow “Q” that works well, especially for tricky mixing but also in some Mastering scenarios. A fairly close third would have to be the Sontec and then the GML, which are both good enough to be desert island EQ's.

In any case, when you reach for a narrow “Q” width, listen for what else is getting removed from the signal and not just the part that needs to go. Also, listen for any resonance or strange artifacts coming from sympathetic Frequencies. My final recommendation to you when using an EQ that has Variable “Q” width is to make use of the settings that sit between typical “Q” widths. Namely, you have EQ's that contain typical fixed “Q” and you have EQ's that contain wider than normal “Q” width, and you have Variable “Q” that can supply the narrow band needed to tricky audio surgery. But, those settings somewhere in between the widest setting and regular setting are not found as often in standard tracking, mixing, and bus EQ's, as is the case with that range between mid “Q” and narrowest. Listen to these settings and become familiar with them, and train your ears to send a signal to your mind, so as to remember what affect these settings have on the audio signal. These settings will have their moments to come in handy.

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How to Mix and Master with EQ – 10 Equalizer Modes – Part Five - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Five – Clean or Colorful EQ

This may seem like a strange choice for a topic on EQ modes. Deciding on a Mode to work with regarding EQ is a decision of how the sound is being adjusted, what affect it will have in the entire range of Frequencies, whether the slope is steep or narrow, gradual or sharp, among many other factors. The design of the EQ itself is a major factor in how the EQ reacts, and though there are many EQ's that share similar design and feature sets, the actual sonic results can be very different based solely on whether it leans more towards a clean or colorful electronic design. When these devices are emulated, their software equivalents will follow similar results.

A good example of how the electronic signal path affects how the same Mode settings are affected is the Millennia Media NSEQ-2 Twin Topology EQ. It allows the user to switch between the highest quality high voltage vacuum tube signal path or the highest quality op-amp solid state signal path that the electronics world has to offer. Using the exact same settings, the way that the Millennia Media NSEQ-2 renders the shape of the exact same setting in Solid State Mode is different than that of its identical setting in Vacuum Tube Mode. One will have a sharper result where the other will be slightly rounder. Both would be considered very precise, but that isn't the only result. Both options are extremely clean, but the subtle harmonic content that is additive, and therefore measurable, has a definite final affect on the audio signal. In my opinion, the brilliant design seems to defy gravity and logic, in that there doesn't seem to be a single setting that doesn't improve the sound. But, it always seems to add something that is pleasant sounding and beneficial to the signal, yet it is so definitively “high end” sounding that you can use it for any mastering project in any music category and never feel that there was a better option. I feel this way about a few other EQ's based on their own merits, but the NSEQ-2 definitely serves as the perfect example since it is the ideal in both solid state and vacuum tube Modes!

Cleaner EQ's may follow a minimalist signal path with few capacitors, no transformers, and minimal wiring. The GML and Sontec are the most famous and ideal versions of this type of EQ. They have plenty of settings to choose from, and they can etch out the narrow troublesome tones or smooth out an entire range of Frequencies, but they do so with very little interference to any tonal aspect of the original signal. They are very clean, but they do not lack musicality. They measure very low in distortion and the timing elements are very accurate, yet still there is something sweetening and polishing about their behavior. Even though they are designed for clarity and preciseness, even the manufacturers can describe the character as one device in their line and another as being more precise as another, or bolder in character and robust. Even in the “clean” camp there is a great deal of variety. Program Equalizers are famous for using oversized transformers, hand-crafted inductors, multiple vacuum tubes, and larger-than-life power supplies.

All of the items in their path are known to have a pleasant additive affect in the signal path, and yet they can be used on the most delicate of Program Material with absolute clarity and precision. It seems that even when there is a small measure of harmonic content and intentional heftiness in the signal chain, we can grab the subtle dynamic character of the source and somehow every detail can shine forth. Somehow, despite very low distortion, an incredibly low noise floor, precise timing elements and lack of phase shift, and an impressive flat Frequency response, we can hear the polish and silk and find it always a pleasant addition. Sometimes the benefits of clarity and color are intertwined and serve no reason or measurement for the reason they perform the way that they do.

We can remove nearly all of this character and find the most perfectly clear and clean Mode EQ in digital form, with no aliasing, no distortion, no harmonic character, and a perfect precision. For the most part, this digital EQ might be capable of matching the exact same setting as a Sontec or GML or Pultec, and it will simply not sound good. Should we use it for mastering instead of the analog choice, even if there is some chance that there is some variation of imperfection that we are unable to measure? It is my opinion that we should always rely on our ears for the final verdict, and if this leads our choices to a preference over a measurement, then we can look at character as a choice in “Clean” and “Colorful” Modes regardless of the design.

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How to Mix and Master with EQ – 10 Equalizer Modes – Part Four - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Four – Linear Phase and Minimal Phase EQ

The usefulness and creative options of an EQ include the ability to separate how one track stands against another and blending multiple sounds together. It defines whether there is a sonic issue that needs correcting, or whether you wish to breath new life into dull source material.

We attach descriptions like “sweetening” and “silky” or “tight” and “punchy” when describing how an EQ affects the signal. When dealing with phase and EQ, considerations move beyond flexibility and layout, and into a scientific realm that some may not wish to concern themselves with. In audio, just like any other discipline, we find that the tools we choose to work with can free us, limit us, or even define our creative decisions. Therefore, we may think of a Mode as simply being determined by the shape of an EQ or the way that it is designed to handle a range of Frequencies or filtering, but Linear Phase and Minimal Phase act as Mode options for the same purposes. Minimal Phase EQ is designed to provide a high quality filtering process that is capable of sounding pure and natural while doing very little to change the timing or cohesiveness of the timing elements of the Program Material.

Phase issues can be the cause of many side effects, but it has become an increasingly small concern with professional gear. In software, phase cohesion takes the role not just of filtering and electronics, but in how sound is handled algorithmically. Therefore, the distinction between Minimal and Linear Phase can involve how an EQ handles actual processing, Gain structure, aliasing and sample rate, edge Frequency filtering, and numerous other issues. Where Minimal Phase can provide natural and precise response, it can also lead to an increase in subtle coloration to the signal the more extreme, and numerous, the filtering options employed.

With Linear Phase EQ, an extremely high fidelity process is used to keep the phase cohesion nearly perfect. The trade off can become more in favor of using less Gain and avoiding audible side effects, and in some cases, trading a bit of artistic musicality for the price of absolute unwavering and pristine timing elements. The choice to favor linearity over proven filtering options with Minimal Phase can lead to ringing and unusual overtones if extreme changes to Gain are attempted, so the choice to use Linear Phase should truly remain hand in hand with making very small, surgical and strategic changes to sound sources. With Minimal Phase, or Minimum Phase as it is sometimes referred to, we have a trade off that finds a balance between the amount of phase a filter allows for, and how well it can provide the shape, slope, and Gain desired. In order to create truly Linear Phase, it has to be possible o adjust all timing elements to the longest potential timing change, which requires a great amount of processing. But, it also places crucial elemental changes to filtering and even can affect the amount of accuracy in actual Frequency and Gain that occur. The most important affect that Phase has on the audio signal is in the sharpness and speed of higher Frequencies, or transients. It is possible for small elements of coloration to occur with any Phase from any EQ that is not purely Linear.

It is my personal opinion that an EQ that claims to be low in timing or Phase shift is generally preferable to Linear Phase, but many Mastering Engineers will disagree. I personally believe that if you listen for the changes that are made, it is much less prevalent to any overt changes in timing to use a Minimal Phase EQ in small amounts than it is to potentially change some of the slope shape and filtering and ripple effects of Linear Phase, at the benefit of near-perfect timing. Whether you are mixing or mastering, the choice of EQ can include specific features like filter type, Gain range, or Frequency settings, and now we can see how the choice of phase cohesiveness can also determine the right choice.

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How to Mix and Master with EQ – 10 Equalizer Modes – Part Three - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Three – Fixed versus Variable Frequency Modes

When analyzing the difference between Fixed and Variable EQ Frequencies, we once again visit the importance in the design and construction of the analog EQ and its purpose. Fixed Frequencies are common in classic Program Equalizers and in Console EQ's. Although they can be the option of any EQ design, these are the most commonly found in these categories, because they were designed with a specific purpose to focus on specific Frequencies that are the most commonly needed for specific individual vocals and instruments.

The filtering process is specifically chosen in the design of the EQ and can help the user work in a consistent and intentional manner that can define their creative signature, but some find deliberate, predetermined limiting and prefer freely adjustable Frequency selection, as is most commonly found in Mastering EQ's. Variable Frequency Modes can not only provide the ability to get more specific and surgical in our tracking, mixing and mastering processes, but it can also be used dynamically as a song effect. Control and automation of changes in Frequency moves can become a musical element in composition, sound design, and mixdowns that cross the boundary of the art of mixing into the art of actual song creation. This brings EQ into a new category, not just for an engineer's task of tracking, mixing, or mastering, but also at the writing stage.

Using EQ as a filter to change the smooth transition of musical content to swell or pass from one Frequency to the next in smooth transition can act like a sonic ocean wave sweeping by, telling our ears that sound is gliding upwards or downwards, creating an actual musical response instead of making corrective changes.

This determining factor draws a strong line between Fixed and Variable Frequencies, showing how there is more to EQ than just quality and preferred uses. Now, we see that creative choices can cross the barrier between utility into the actual writing of music. Next, lets take a look at Linear Phase and Minimal Phase EQ's.

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How to Mix and Master with EQ – 10 Equalizer Modes – Part Two - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Two – Boost and Cut EQ

When outlining EQ Modes, we can see that the design of the hardware EQ involves different electronics in the signal path to provide the range of Modes and functionality. I state this because the way in which we interact with EQ in tracking, mixing, mastering, includes Modes that are fixed and selectable, and Modes that are directly affected by the device's construction. In the format of EQ's, we find that different era's and design philosophies provide a different reasoning for the Modes that are provided.

Since I wish for this discussion on Modes to deepen your appreciation, understanding, and decision-making of the 5 EQ types mentioned in the first Post series, I wish to start this series by looking at Boost and Cut Modes in various EQ's. It may seem that Boost and Cut should always mean the same thing and should always be provided as a single option. Since the terms “Boost” and “Cut” may appear obvious and self-explanatory, you may be wondering why I would start with something so seemingly surface. I would reply that the presentation of Boost and Cut is more telling of the use of an EQ than we might assume.

Some designs, including early Program Equalizers, may provide separate controls for Boost and Cut. Many users may not be aware of this, or give it much thought. Since it has become a central part of the mixing process to use digital tools that emulate their analog counterparts, it becomes equally relevant how Boost and Cut are presented, both inside and outside the digital realm. When Boost and Cut are separated out independently, they may also provide different Frequency options for Boost than are provided for Cut, and they may also provide a slightly different Band shape. If both controls are simultaneously usable, this provides a flexibility that we would not tend to consider on our own. You may be able to reshape the Frequencies around a certain range by overlapping the shape of Boost on top of the shape of Cut, thus bending and molding the waveform to lean towards a musical response that brings multiple instrument qualities together, or reduces a wider palette while accentuating and focusing specific narrower instrumentation.

The flexibility in this design is intentional, and though it may seem that separating out Boost and Cut is an antiquated way of handling EQ tasks, it may actually open up more possibilities than our standard Boost and Cut expectations. Normally, we will find Boost and Cut as a single Gain controller in analog and digital form. The Frequency choice, shape, slope, will have its control, along with a separate control for Boost and Gain. Inside the digital domain, we may have tools that go beyond the traditional barriers of analog EQ's, giving us ways to bend, shape, and mold Frequencies and Gain that are far more flexible than what we have seen in the past. Along with these freedoms comes new responsibilities to make the best choices that favor the audio impact over the visualizations provided. Next, I will discuss Fixed versus Variable Frequency EQ Modes.

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How to Mix and Master with EQ – 10 Equalizer Modes – Part One - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part One – Introduction

I have outlined 5 specific types of Equalizers in my previous Posts. There are different ways to categorize EQ's and these are not the only types that one could separate to classify or define, but I believe that I've provided a viewpoint of categorization that helps us to look at EQ's in the manner that we need to utilize them and this viewpoint serves us best. Now, I would like to share with you what I would outline as 10 EQ modes that you will come across. Again, this can help in selecting the tools for the job that you will need the most and to know what to use at a given time. The term “mode” is used in a broad context for this series of articles to make the idea the most beneficial to you.
These 10 EQ Modes are the following:
1. Boost and Cut
2. Fixed versus Variable Frequency
3. Linear Phase versus Minimal Phase EQ
4. Clean or Colorful
5. Fixed “Q” width versus Variable “Q” width
6. High Pass, Low Pass
7. High Cut, Low Cut
8. Band or Bell Shape
9. Shelf
10. Graphic or Parametric

In Part Two of this series, I will discuss Boost and Cut EQ Modes.

How to Mix and Master with EQ – 5 Types of Equalizers – Part Five - CDSoundMaster.com

Audio Recording with Equalizers – 5 Types of Equalizers – Part Five – The Outboard Equalizer

The final type of EQ I want to define is the Outboard Equalizer. In the same way that I have singled out a Console EQ or a Mastering EQ, the Outboard Equalizer can have many overlapping qualities shared with other EQ's. Most modern Equalizers would be considered Outboard EQ's. It has a technical meaning but also an assumed meaning in purpose. The Outboard EQ is simply a hardware device that is not hardwired into the rest of an integrated system. It is designed to offer its sound capability whenever the user wishes to implement it, and it is intended to be left out of the signal chain until it is needed, so the Outboard EQ is designed to sit in an outboard rack awaiting its use.

The Outboard EQ is designed to provide use beyond what is typical of the average in-line EQ or Console EQ, and each Outboard EQ brings its own qualities and characteristics. Some Outboard EQ's are designed to fill a specific gap that is not covered elsewhere. This can be an economic gap, where the user needs something that sounds nicer than their low-to-mid line Console, but is still more cost effective than a $6000 Mastering EQ, and others might consider that Mastering EQ the perfect choice as an Outboard EQ. Other Outboard EQ's might be a graphic Equalizer, designed to control specific set Frequencies without further adjustment options. Other designs could even be Console EQ's from consoles that are different than the one installed in the studio. For instance, a person may have stereo pairs of Outboard EQ's specially racked that give them 1960's German Equalizers that come from a German console, while their studio uses a British in-line Console. They can patch the Outboard EQ to get a different musical flavor from a Console that would be too costly to install the entire hardware.

Other Outboard EQ's include items like Mastering EQ's and Program Equalizers already designed. It is equally notable that some of these EQ's actually started as a prototype for use as a recording or mixing console and gradually became more beneficial as separate EQ devices. So, their very existence helped to define this new EQ category. An Outboard EQ can help a studio diversify its offerings to clients, and it can raise a studio's profile when displaying its “equipment list.” Some Outboard EQ's become popular for their qualities for vocals, and others may act as special filter devices for guitars and bass. The possibilities are endless for the Outboard EQ, and the bottom line tends to be quality, flexibility, and offering something that is either different from the installed Console, or that offers something unusual that the user would not need multiple channels of. The Outboard EQ offers the small studio and independent producer access to excellent devices that they could not afford in larger quantity, and offers flexibility to the larger format studio.

Formats like the API 500 Series provides a perfect scenario for this type of add-on adaptability, where a single power supply range can be used to swap out modules of various devices. This was originally developed to provide the user of an API Console the ability to add a variety of API devices to patch into their API Console. This could act as a sidecar, or it could be a portable version of their favorite API channels. The usefulness of this power supply was slowly recognized by other 3rd party manufacturers, and by formatting their own independent designs to the power supply requirements and card size, they could supply their EQ's to studios using this outboard power source. Since they can be swapped out, this becomes cost effective and provides a great amount of flexibility to the user, and further widens the expanse of external analog hardware choices.

How to Mix and Master with EQ – 5 Types of Equalizers – Part Four - CDSoundMaster.com

Audio Recording with Equalizers – 5 Types of Equalizers – Part Four – The Console Equalizer

The next EQ that I want to describe is the Console EQ. We have a much wider range of diversity in quality and features in the Console EQ than the other categories I describe. Some Console EQ's are just as high a quality as any Mastering EQ, but there is still something that defines them as a Console EQ. The primary purpose of the Console Equalizer is to provide Frequency adjustments within a single channel of a multi-channel mixing system.

By design, the Console has multiple channels connected side by side, each one carries its own separate audio path. Most Console's are designed to handle Mono audio channels, but some offer the ability to run stereo pairs for each channel. Console's come in as few as 4 channels mixed to 1, but typically you will find that a professional Console from any era will be a minimum of 4 channels to two channels. The most common Consoles are 12x2, 16x2, 24x2, 32x2, 48x2, and 64x2. Modular Console designs offer any number of channels above 64 that a facility might need. There are in-line Consoles that can switch the audio path to and from a recording device, and there are others that are twice as wide with just as many “mix” channels as there are recording channels. These designs also include a variable number of “Bus” groups, meaning that channels can be sent to a sub-group before the final stereo output, which may look like a 24x4x2 configuration or similar. There are also fully configured surround processing Consoles that have a multi-channel output in addition to the stereo output, so that a music mix can be automated at the same time as a film-track mix output.

So, where does the Console EQ fit into all of this? The Console EQ is used in the signal path of the individual channels. A device plugs into a single channel, usually signified as a line input, direct inject or direct input, or a microphone input. These three possible levels use their own connection type and their own impedence and draw their unique amount of source current. These devices are sent from the channel input through gain level adjustment and channel fader control. In between the input and output is the EQ circuit. This allows the user to make adjustments to whatever the device is plugged in. If the device has a low rumble, the Console EQ can provide a low cut filter or a high pass filter. The user may want to “print to tape” certain shaped Frequency adjustments that they consider a part of the source sound, boosting or cutting problem areas or enhancing the original signal to suit the needs of the track as it is recorded. The Console EQ can serve a purpose going to a recording device and it can serve a second purpose when mixing. You may wish to prepare the track for using the recording channel the best way, merely cleaning up the signal, and then make some creative mix decisions after the track is recorded.

The Console provides something unique from other EQ's in the fact that it is in the signal path of the original input item as it is being prepared to be recorded. In one sense, the Console EQ is merely in a convenient location to apply the same potential kind of EQ as any other category EQ, but the truth is that the fact that it is within a signal path that is designed to provide amplification to the original source signal means that this can be used as a part of the creative element in recording. You can combine the quality of how clean the input signal is or you can gently saturate the signal to add some effect to the signal as it is recorded and Equalized. The other defining character of the Console EQ is its use after it has been recorded.

The EQ can now be patched from the recording device into the same position of the channel that was used to record. The EQ can be used going to the recording device and from the same device once recorded, so it can serve two purposes using a different combination of the same Frequency bands. The Console EQ is provided for convenience, meaning it is ideal for a wide range of uses and does not need to be patched from an external source for use. It is designed to provide the Frequency adjustments that are most commonly needed. Indeed, a great Console EQ can do everything that most high end EQ's can do, with the addition of always existing within the context of full gain and volume level control. Typically, the Console Equalizer has fixed Frequency positions, and may have fixed or smooth gain levels. Some Console EQ's have fewer choices in how high the Frequency range can select, since it may be focused towards individual levels of a voice or instrument, where a Mastering EQ may have unlimited control of highs. But, many Console's have full shelf control in this area. Some Console EQ's are not as high a quality, largely because the quality of the EQ is factored into the overall production cost of the Console. In the late 1980's the market for budget consoles first began to emerge. There were smaller format and inexpensive Console's before this point, but there were very few options of any substantial quality below the $1000 mark. The channels were limited, the EQ's were sub-standard, and the usefulness of the overall signal path was only good enough for demo use. Inexpensive live mixers had very little power and few channels and generally sounded terrible at the sub-$1000 price point. Truly, a decent mixer started at $5000.

In the 1990's, production quality and manufacturing led to some of the first high quality designs for 16 channels of good sounding signal and EQ under $1000. Ten years later, these same features are found in comparable devices at 1/w the price and twice as many channels. The modern audio interface does not come with its own analog EQ signal path, but contains a better average sound quality than devices that used to cost ten times more. The modern concept of the Console is maintained more in the form of the DAW than in analog form, but most professional recording facilities still contain at least one high end room with a real analog Console. The highest quality Console EQ's are not only distinguished by their design, cost-per-channel, and efficiency, but are also recognized by the designers themselves.

Many Console EQ's gain a status of their own because they were designed for the mixing process by people who have become famous for their ability to understand the artistic process, the goals of the producers, musicians, and engineers. Because of this, along with their quality, has made many classic Console EQ's something that many world-class Mastering Facilities use. Whenever this is the case, they are usually found in stereo pairs of original Console channels, and not an entire Console. This is for its use, space, cost, but also because the channels can be used in a direct signal patch and this shortens the signal traditionally feeding the channel to a group or master out, which has more electronics in the chain and can very slightly degrade the signal. Other facilities go so far as to only contain the EQ portion of a channel, making the signal slightly cleaner, but perhaps missing some of the musicality desired from the channel.

How to Mix and Master with EQ – 5 Types of Equalizers – Part Three - CDSoundMaster.com

Audio Recording with Equalizers – 5 Types of Equalizers – Part Three – The Mastering Equalizer

Mastering has become one of the most misunderstood and complex aspects of music production. It is primarily about simplifying everything that has come before this stage, but because it is a skill that has such crucial consequences, it is a profession and skill that is set apart from recording and mixing in many ways. Therefore, this description of what makes a great Mastering EQ, I will first give a brief overview of Mastering as a process.

When dealing with recording, we might be concerned with elements like learning the different types of microphones that there are and when to use them, what the best preamps are, how to tune instruments, how to set your levels for recording and for headphone balance. If we were looking at the elements involved in the mixing process, we might talk about the purpose of the sections of the analog mixing console or what a DAW is and how to use it. We might cover how to set levels and bus groups and how to effectively use channel EQ's the best way.

With Mastering, the first thing that we should assume is that the Recording and Mixing stages of the process are complete. Once everyone is happy with how the recording process has gone, they can work towards getting a proper balance of tracks, adding whatever effects and fine-tuning may be involved in providing the final result they envisioned, hopefully even exceeding their expectations. Once this final mixdown process is complete, the recording will normally be a stereo Master, or Pre-Master, depending on who you ask and what stages are expected. Now, we enter the Mastering stage of the process. In Mastering, there is nothing that can improve upon an absolute perfect Mastering Session. In my opinion, the ideal, absolute perfect Mastering Session involves a single listen through, under ideal conditions, of the entire Program Material, at which point there is quite literally nothing that the Mastering Engineer thinks should change, other than the spacing and ordering of song tracks, and any personalization of track information like tracking codes, artist and writer and label information, etc. In an absolutely perfect world, the best Mastering Session would last about an hour longer than a listen through of the album, and nothing would change.

This would re-enforce the artistic and engineering decisions made from recording to mixing down, with everyone having done such a remarkable job, even down to tuning their instruments, that there is nothing to change or enhance; not even the balance of levels from one song to the next. In this amazing, and almost non-existent imaginary event, it truly does not matter what equipment the Mastering Engineer owns in regards to their EQ or other Outboard analog gear. The only elements crucial would be their brain, ears, room qualities, position, speakers, amplifiers, and cables. The ability to listen, concentrate, and process what is heard would be the elements that matter the most. As you may have already guessed, Mastering usually involves more than listening and inputting some relevant file data. Usually, the mere process of the mixing sessions alone are partly what leads to the need for a great Mastering Equalizer. In our “perfect world” scenario, the balance from one song to the next would have to come not just from good sounding, individual song mixes, but a balance that makes so much sense from one to the next, that these translate to a consistent perceived volume level throughout the entire project. This is not common in almost any group of songs that are born out of a studio recording environment. Even if every musician stood in exactly the same position for every song, and every microphone remained at the same distance, and every dial remained the same, and everyone was remarkable at maintaining a consistent performance and energy, and the range of musical material had a perfectly arranged flow from one song into the next, the likelihood that every element would be brought together with absolute perfection to such an extent that there was nothing to benefit from any further adjustments at the Mastering stage is unbelievably slim. This does occur every rare once in a while, but inevitably there are going to be some tracks on an album that hold the other performances or mixes to a higher standard, and this alone can leave the Mastering Engineer some work to do their best to raise lesser tracks to the audio fidelity of the album's best tracks.

No matter what the actual scenario involves, there are certain qualities that a Mastering Engineer requires from their Mastering EQ's that are unique compared to any other EQ. Once again, there is always some overlap. Since the standards are very high when it comes to an ideal Mastering EQ, one can assume that a Mastering EQ is also going to perform amazingly well for Bus groups and Mix EQ challenges. In fact, it is nearly impossible for a great Mastering EQ to fail at other tasks, but not every Bus or Mix EQ is going to be perfect for Mastering. The Mastering EQ is going to be a stereo EQ or a well-matched and calibrated pair of Mono EQ's. The quality of the EQ needs to be capable of maintaining the integrity of the original recording without removing any volume, timing, phase, stereo imaging, noise, or headroom.

It will favor clarity over musicality or positive coloration in character, but the perfect Mastering EQ has the ability to add a very subtle musicality even while remaining incredibly clean. Typically, we might be looking to add something with character at earlier stages in recording, making an artistic statement in the writing of the music itself and in translating it to a working mix. A recording may be slow and fluid, or sharp, fast, and articulate. The sound maybe rich and ambient, or may change pace and instrumentation. These musical qualities may nod towards different Mastering EQ's. Some Mastering EQ's are designed for precise response by minimizing the amount of electronics in the signal path and synchronizing how each Frequency is adjusted, where other Mastering EQ's use extremely high quality electronics that add color, but in a precise manner that works well with sound adjustment. Transformers, Op-Amps, Tubes, Capacitors, and even wires and cables all add some measure of personality into the sound process, and high quality parts can remain clean and transparent enough for any audio task while allowing the user to decide which of these characteristics will make a good match for a song or album. Mastering EQ's need to have enough variation to work on a wide range of tasks, but vary in their approach.

With Program Equalizers like Pultecs, there are several separate bands that each perform a task, focusing mostly on fixed Frequencies and broad strokes, with some adjustment of actual “Q” widths. Other EQ's like the Sontec, GML, and Millennia Media Mastering EQ's provide overlapping ranges of Frequencies with variable “Q” width, some with the ability to repeat gain settings with detented positions and some with freely moving positions. The GML and Sontec are known for their excellent clarity and flexibility, with multiple options of width and Frequency. The Millennia Media NSEQ-2 is famous for its flexibility, but also for its amazing coloration, its wide interpretation of “Q” width, and its dual topology, providing the highest quality high voltage tube path and separate op-amp solid state option all in one unit. It is designed to work in 2dB steps, and although it can be set to small increments, the device is designed for wide “Q” and large steps that amazingly do not harm the signal.

Musical choices are just as important with a device and its diverse range as its ability to precisely and accurately make adjustments. Mastering EQ's generally offer the ability to do high pass, low pass, high and low cut, narrow, medium, and wide bandwidth bell-shaped EQ, and high and low shelf EQ. The exact shape of each part of the EQ is individual to the Mastering EQ design, but generally leans towards precise response over stylistic options. One thing that many are not aware of, is how non-linear some of these designs actually are. One of the most wonderful capabilities of the Nebula Pro Plugin, and our CDSoundMaster Nebula Pro Program Libraries, is the perfect reproduction of these analog settings. No longer is it difficult to reset the same settings over and over again. But, also within this capability, we can see just how non-linear these “precise” devices actually are. There are very few EQ's that offer a precise actual change in gain from one step to the next. It may look and sound like an even step, but when we see the results, we realize there are many changes occurring that are contrary to the settings marked on the front of the device. We have always made the best decisions as Engineers, though, by following our ears in these matters. A great Mastering EQ sounds great because it sounds correct to our ears. We certainly know we are in the vicinity of accuracy with them, but we have used them for over 50 years without any visual representation of what is actually occurring.

Now that a novice user can spend a few hundred dollars for a perfect digital archive of the most expensive and historically valuable hardware created for use with sound, they can visualize what is occurring with very little genuine knowledge of what it means. My advice is to remember that the end result is about what sounds right to our ears. No one, including Mastering Engineers, can afford to be so elitist and lofty as to think that absolute scientific perfection is a standard that we have ever had the benefit of ascribing to. That is until the digital age, at which point we immediately started developing software to try to make things sound less accurate, like analog. Why? Because it sounds good and digital is a black hole when it comes to sonic personality. It is my opinion, that the things we embrace about the perfect Mastering EQ also point to their wonderful inaccuracies just as much as their ability to get an amazing, surgical job done.

How to Mix and Master with EQ – 5 Types of Equalizers – Part Two - CDSoundMaster.com

Audio Recording with Equalizers – 5 Types of Equalizers – Part Two – The Mix Equalizer

It will become increasingly apparent that each EQ type has its obvious distinctions, but there is always an overlap when defining categories. In the first Post I described the Program Equalizer, which includes its usefulness for voice, its continued usefulness for entire song mixes, and its enduring qualities that make it just as necessary today as it was in the 1940's. Now, I will share with you some distinctions about the Mix Equalizer. The most obvious determining factor for a Mix EQ is its usefulness for bringing an entire song mix together at the mixdown stage. So, what are these qualities that make for a good Mix EQ? The first one is the assumption that it is a stereo EQ. This can, of course, be two precisely matched Mono EQ's, but most often, when an EQ has been specifically designed to work on full, modern Program Material, it is assumed that it will likely be a stereo device. The next assumption about a great Mix EQ is its accuracy. A Mix EQ is going to be selected for many features and sonic qualities, but its accuracy to reproduce the full range of Frequency spectrum is a deciding factor for use in mixing. This also means that it is able to provide a high quality signal. This doesn't just mean that it can provide Frequencies that are ruler flat, but that it can do so with a very low noise floor and what we would call an extremely high “headroom.”

Headroom is defined as the device's ability to handle incoming volume maximum output, and truly also dynamic material, with enough volume clearance to avoid getting distorted. To describe headroom further, I will go into just a small bit of detail of the difference in digital sound and analog sound. With digital, we essentially have a volume clearance of a maximum of 0dB. This means that we cannot allow the volume of our mixes to exceed a digital reading of 0dB. Anything louder is known to distort. The actual true response of this characteristic happens in the translation from digital to analog. We can actually overcome the “headroom” of digital distortion at maximum volume levels with the quality bit depth. We should always actually consider the bit depth as starting at 0dB and counting downwards to lower and lower volumes, but the truth is that when a device is as high a quality as something like the Nebula Pro plug-in by Acustica Audio, and our CDSoundMaster line of program libraries for their plug-in, and our growing line of independent VST plug-ins that use our own technology along with the Acqua technology developed by Acustica Audio, you have a 64 Bit Depth quality. You can input so much volume into this signal chain that it is virtually impossible to overload the signal, but the analog recreation of the signal within the plug-in includes the actual analog response of a device, which means that you won't be overloading anything digitally, but it is possible to overload the device emulated. But, once it leaves the plug-in, it is translating back into analog, at which point the volume must be reduced beneath 0dB once again in order to clear the digital-to-analog headroom.

With Mix EQ's, this headroom is seen in purely analog terms, which are centered around something different than digital. Where digital has a 0dB ceiling that cannot be crossed, in analog we have a “best case scenario” that we call unity gain. This level is the point at which a device performs at its best, which is a level that is as high above a noise floor as it can be, which means it is as loud as it can get above the noise floor. Unity gain is also defined as how clean the signal can remain before it goes into any measurable distortion. When the signal gets louder, it improves its signal to noise ratio, which is what we want to achieve, but once we increase the volume beyond unity gain, we start to introduce harmonic distortion into the signal. Depending on the device, the Producer, Audio Engineer, or Mix Engineer can develop a palette of creative abilities by learning what the saturation qualities are from their range of equipment, because some devices begin to introduce a pleasant sounding smooth, gradual saturation process that can intentionally enhance Program Material as it passes through the device. Typically, a great Mix EQ is either so clean that it never reaches a point where overloading the device is of concern, or it is intentionally “tunable” to get the exact colorful response that the user wishes to achieve. It is common that a Mix EQ has a fixed setting for volume, meaning that it is designed to run very clean, with a low noise floor and extremely high headroom, so that it simply does not matter what volume you set your audio signal at the EQ's input. In other designs, the signal chain can be selectable, meaning that you may be able to adjust the input or output levels to match the signal you are working with. This usually is introduced in the EQ's design when the manufacturer is also offering the ability to slightly alter the saturation point of the EQ's signal. Another defining quality of the Mix EQ is the type of filtering it provides. What kind of EQ options should we expect to get from a great Mix EQ? One format is the same as the traditional Program Equalizer, but in stereo form, and using the mid-to-late 50's ruler flat response. This design can include a low Shelf and high Shelf eq, which can boost or cut the volume an extremely wide range of Frequencies that start at a certain point and include everything above or below that point. These can often include a selectable range of mid Frequencies and high Frequencies. These Frequencies in the Program Equalizer format will usually be set or fixed, meaning that the device provides specific Frequencies that cannot be changed. But, many of these devices allow you to select how narrow or wide the “Q” width will be on these Frequencies, which can make it musical and flexible, both of which can be a determining factor for how well they work on an entire mixdown.

Other Mix EQ's are designed with greater flexibility at all Frequencies, with the ability to select multiple bands and multiple filter shapes. Flexibility matched to a high quality sound can make it possible to bring elements of a mix together in ways that could not occur when working only on individual tracks. The ability to select Frequencies and shape them into a variety of responses can be very subtle or it can completely transform the mix into something much better than making changes to individual tracks. The Mix EQ is often just as useful as a Bus EQ and a Mastering EQ as it is for final mixdown. Because each of these stages can involve a complex combination of different musical elements being brought together as a unified recording, the Mix EQ should commonly be expected to perform just as comfortably at Bus and Mastering tasks. Even so, there are some identifiers that make for ideal Bus and Mastering EQ's that can differ from the Mix EQ. It should be assumed, overall, that the Mix EQ is synonymous with Bus EQ tasks. This includes maintaining an extremely good signal to noise ratio, a desirable range of clarity, quality, and flexibility in controls. The actual combination of these abilities are extremely diverse, but the end goal is the same: being able to operate on a combination of individual tracks that are being mixed together in such a way that allows the user to bring the tracks together, enhance their combined sonic quality, and or make corrections that are apparent once parts are combined, so that the final outcome is better than if the user were only operating on individual variations of independent tracks.

By having the right Mix EQ for a given scenario, you are able to control the final outcome of your mix with a wide range of options. The tools that you use should not rule over you, but are a determining factor in the creative and technical choices you make. They can help you to define who you wish to be as an Engineer or Artisan. The final result of a mix often becomes the signature of the operator, so a useful combination of quality and quantity make for a healthy set of tools to bring you closer to your goal in excellence. The following is a list of EQ's that CDSoundMaster has created which are excellent for use as Mix EQ's. Some of these are more precise than others, and many have an extremely different set of features from each other, but they all include characteristics that can be excellent for your Mix, Bus, and Mastering tasks.

The Nice EQ VST
The SongTec MEP 250 EX for Nebula Pro
The Mastering Suite for Nebula Pro
The GEQ - The Great Mastering EQ for Nebula Pro
The Tube Trek PE1C for Nebula Pro

How to Mix and Master with EQ – Introduction – 5 Types of Equalizers – Part One - CDSoundMaster.com

Audio Recording with Equalizers – 5 Types of Equalizers – Part One – The Program Equalizer

There are Fixed Band Equalizers and there are Variable “Q” Equalizers. There are EQ's that are optimized for Mixing and there are EQ's that are perfect for Mastering. There are EQ's that we typically use on individual tracks and there are EQ's that we like to save for Bus Mixing and Master Outputs. This first Post is about identifying the main types of EQ's and their purposes. This can help you identify the tools needed for different scenarios, and can help in purchase decisions down the road. The five primary categories of EQ's I will define here are: Program Equalizers, Mix EQ's, Mastering EQ's, Console EQ's, and Outboard EQ's.

The first thing to know about these EQ types is that they can overlap. Many Program Equalizers are used for Mastering and for Mixing, and most Program Equalizers are also Outboard EQ's. Perhaps the mere amount of 'crossover' (pardon the pun) contributes to the confusion that surrounds the deciding factors in the best EQ's to use for a given job. I also consider the corresponding cost affixed to EQ types a confusing factor when deciding on the best EQ's for a given job. Let's go ahead and assign a description to each of these five distinct EQ types, starting with the Program Equaliser. The Program Equalizer is a type of EQ that is most famous for the Pultec-style EQ, like this original vintage Pultec EQP-1 that CDSoundMaster created specifically for Acustica Audio. The Program Equalizer provides a wide range of options and frequencies, and is defined by its usefulness on a wide range of “Program Material.” Program Material is defined as main tracks, or final audio sources, that are used for programming, whether they are pre-recorded audio masters of music content, or a live broadcast program that is output to a radio frequency band, television transmission, or, in our modern world, for an internet stream. Program Material is the final combined output of a professional sound source.

In song or in album form, Program Material is the final song track that has been mixed and mastered, or it is the entire album made of a combination of songs. In Broadcast, the Program Material has traditionally been the primary voice content of the Broadcast, but has included musical performances, events, and a limitless range of Programming. Historically, the Program Equalizer was designed to provide the Audio Engineer immediate access to Frequencies they might need to adjust in order to improve the clarity and professional quality of voice content. Since the sound range attributed to voice content, and the final Frequency output transmission of early Broadcasts was typically around 12kHz Maximum, Frequencies typically were rounded off at around 15kHz, tapering down 5dB every 1000 cycles or so until they reached above 20,000 Hz where they were further reduced. These extremely high Frequencies would not contain material that could be correctly reproduced over the air, and leaving these in the signal could cause a build-up of interference and cause unwanted transmission and reproduction issues. Optimizing the signal for the Frequencies that could be reproduced accurately was the strong point of the Program Equalizer.

The Program Equalizer has been around at least since the late 40's in their current form that we still use today, but it's use has changed over the years. One thing that has distinguished it from other Mastering Equalizers is the fact that it is typically a Mono device. The highest quality Program Equalizers can be matched to each other so that they are useful as a Stereo pair for modern mixing and mastering use. The fact that these EQ's are typically Mono is due to the fact that all early primary recording sources were also Mono. Radio programs were Mono, as were early recordings. In the 1940's through the 1950's, and even part of the 1960's, the audio spectrum was controlled to limit the high Frequencies above 15,000Hz and to tailor the mid and upper Frequencies with a wide range of quickly accessible controls, along with the ability to enhance broad ranges of lower Frequencies while focusing on reducing boominess and muddiness that could affect clarity in Broadcast and recording. Increasing the gain in upper frequencies could remain smooth and articulate because the slope reduced anything above 15kHz that was not going to be transmitted, and would not typically translate to earlier recordings. In the late 1950's and into the 1960's, the quality of Program Equalizers was well known, but its usefulness expanded as the range of capabilities of recording expanded. Stereo recordings led to the need to calibrate two independent Program Equalizers that could operate together, balancing the left and right channels of recordings, but also the ability to control the bass Frequencies in the center of a mixed recording was necessary for controlling needle movement on a record player.

As High Fidelity recordings grew closer to our modern full-range listening experience, many Program Equalizers, along with other recording devices, leaned more and more towards a full-range capability. No longer were there filters intentionally designed to buffer out extended high Frequencies, but rather they were designed to make a ruler flat response. Still, the incredible quality of earlier Program Equalizers were recognized for their detail and this has continued in modern day use, where we find it is possible to simply boost more high Frequencies with early Program Equalizers, since the cut slope that occurs above 15kHz tends to simply reshape high Frequencies into a Bell-Shaped curve instead of a flat Shelf-response. The exact same lines of Program Equalizers, like the classic Pultecs that we still use every day in modern studios, both in their real hardware form and as software equalizers, exist in their original form and more often in the form of the flat response in extended Frequencies. They are used for individual tracks, bus groups, final mixdown, and for mastering. They are ideal for individual vocal tracks, since the original Program Material focused mainly on vocals, but the high quality sound and structure in design of Frequencies is useful on literally any sound source that needs fixing or enhancing. An example of a typical Program Equalizer would include a combination of a Low Cut filter, Low Boost and Cut Frequencies with Gain control, a wide range of Mid Frequencies, with or without a “Q” Width control, High Frequencies, typically using fixed Width and boost and cut Gain, although some only have one grouping for boost or cut, and potentially a High cut filter, and often they alternately contain High and Low Shelf EQ's. I will go into detail about these different type of filter options in a later Post.

As you can see, the history of the Program Equalizer has changed over the years alongside the changes that have occurred with actual Program Material. We have AM and FM Radio, Digital Radio, Internet Broadcasting, Digital Cable and Satellite Television, DVD's, Blu-Rays, and new content formats coming every year. The Program Equalizer seems to hold its own with amazing analog sound through every transformation our technological audio world experiences. The following are some of the Program Equalizers that CDSoundMaster has chosen to provide as VST Equalizers and also as audio software to be used with the Nebula Pro Plug-In:

The Nice EQ VST - Inspired by the NSEQ-2
The Peak EQ VST - Inspired by Summit
The Tube Trek PE1C for Nebula Pro
The GEQ - Great Mastering EQ for Nebula Pro
The SongTec MEP 250 EX for Nebula Pro
The Cooltec EQP-1A3S for Nebula Pro
The Cooltec MEQ-5 for Nebula Pro