How To EQ – Mixing and Mastering - CDSoundMaster.com – 12 EQ Issues Part 1

Audio Recording Issues – Introduction Part One

The topic for this series of Posts is about specific audio recording issues that commonly come up in the tracking, mixing, and mastering processes. The Audio Engineer often plays a combination of these roles in the chain, or may specialize in a niche position.

I have addressed an outline of 5 specific types of Equalizers and how they are used in daily tracking, mixing, and mastering. I followed this with covering 10 common EQ modes that we work with under these 5 categories of EQ designs, both in analog and in digital domains.

Now, I would like to break this down into a process of analyzing 12 specific scenarios that we face, with a groundwork provided of EQ types and EQ modes. What situations arise that call for us to be the EQ Artisan, making creative decisions, and when do we run into EQ emergencies that call for an EQ surgeon? Although the situations are ongoing and extremely expansive, I have outlined 12 specific scenarios that I think are interesting to discuss at length. I began this topic throughout my 2013 Blogging year, but as many of you know, it has been an incredibly eventful year for audio recording, including releases and updates that CDSoundMaster has taken part in with Acustica Audio, like the Cooltec EQP-1 Audio Plug-In that we are so proud of, and our independent Nebula Pro libraries that we believe are among the world's finest audio processing options available today. Needless to say, my Blogging has been unsteady, and has shifted topics many times throughout the year as a result.

So, I am going to begin this topic fresh, uninterrupted, and I hope that it serves as an informative tool for you. As I have stated in the past, we use tools in order to leave a creative mark on our work. We define our artistic decisions with the hope that they provide a signature, whether it is a strong artistic statement or the decision to always remain true to the song or music style. Productions are approached in so many different ways, and every choice can have a profound effect on tracking, mixing, and mastering.

Regardless of your approach, you want to be sure to identify key factors in making improvements to your mix. The following is list of scenarios that call for important EQ decision making in tracking, mixes and mastering:

1. Actual notes that are out of balance.

2. Overtones that overstay their welcome

3. It sounds great on its own, but...

4. Nice sound when tracking, but way too much "-----" when blending parts together

5. Multiple mic's setup to track the same instrument and need the right balancing together

6. Two birds, one stone

7. Separation or glue

8. Overlap in the mix causing unwanted frequency bumps

9. Compressing and limiting changed something that needs to be fixed

10. What happened to my stereo field?

11. Comb what?

12. Making it stand out or bringing it all together

These processes come up all the time in music production. Every Audio Engineer has their own approach to address these situations. There are also Producers, Engineers, and others involved in the recording industry that have not run into these issues, or have not been equipped to handle them. Addressing these situations can show the myriad of scenarios to help prepare those that have never run into them, are lost as to how to handle them, and also those that are well-trained, but may be looking to broaden their experience and offer more ways of approaching the same situations. This is also about showing how the mastering process can lend information to the Mixing Engineer, providing ideas about how to better prepare recording sessions for a successful outcome.

How to EQ – 10 Equalizer Modes – Part Eleven - CDSoundMaster.com

Audio Recording with Equalizers – 10 Equalizer Modes – Part Eleven – Graphic or Parametric EQ

The final Equalization modes that I would like to discuss are Graphic and Parametric EQ's. These are two different modes, but since they are the two primary choices of EQ design that the user will choose between, I wish to close in a combined discussion on these modes. There are other EQ's, like Paragraphic among others, but Graphic EQ and Parametric EQ are the two predominant operation modes. You can technically design an analog Graphic EQ and Parametric EQ using the same basic signal path, and therefore with the same sonic integrity and character. However, they provide a noticeably different range of possibilities.

The Graphic EQ is defined by having multiple fixed Frequencies, each with their individual Gain, all available at the same time. We see these everywhere from live sound installations to car stereos and home stereos. Because the Graphic EQ is used so commonly in many scenarios outside of the studio, some people make the mistake of thinking that it is not meant to be used in the studio at all. In some ways, we truly tend to under-use the Graphic EQ. It is largely because the Parametric EQ was such a radical invention at the time it was developed, that it become the norm in most EQ designs. For the Console EQ, Parametric makes perfect sense, because the user can be provided a lot of flexibility in a small linear space, where a Graphic EQ on every channel would take a lot more space. For Outboard Equalizers, we often see the Graphic EQ being used to control the balance of the outputs in a given room, to EQ the speakers themselves, or for monitoring in multiple scenarios. Many live mix Consoles will have a Graphic EQ on the main output, which perpetuates the belief that Graphic EQ is not used in typical tracking, mixing, or mastering.

The reality is that the best sounding Graphic EQ's can be an incredible mixing tool, and although they are almost never used as such, they can be incredible for Mastering as well. In general the Graphic EQ tends to provide each EQ Band at the same precise width, with one Band backed up to the next. Since each band controls its own independent EQ with the same amount of boost and cut Gain, you can sculpt the entire output spectrum with individual control. With a Parametric EQ, you have various individual modes that help shape the output and the Band EQ's can be used in a flexible manner that we will not find in a Graphic EQ, but in the case of the Graphic EQ, we can add and subtract exactly the amount that we wish to for each part of the Spectrum needed. This can work wonders on individual tracks and on the main outputs. The Parametric EQ was originally designed for hand-built mixing consoles that became the world famous GML and Sontec lines of mix and master EQ's.

The Parametric design is believed to originate with these developers. The Parametric EQ was the first design that allowed the user to tune in on the exact Frequency desired, adjust the “Q”, and even select multiple bands for specific tasks, some of which could even overlap other bands. Since the Frequency, width, and Gain are all adjustable, the user can fine tune their EQ needs with a great measure of flexibility. Because we have become so accustomed to having the Parametric design for many years, it is hard to imagine not having this flexibility available to us. In analog form, the Parametric EQ provides us the structure, and the construction of the individual brand of EQ provides the individualized sound character.

Inside the computer, we are presented an increase in visualization options for the Parametric Equalizer, showing the movement of Frequencies, the width options, and allowing us to grab, bend, and stretch positions while seeing the shape on the screen. The Graphic EQ tends to exist in the digital realm as an emulation of the analog device, usually only adding the flexibility of input and output levels and volume visualization. I highly recommend exploring the EQ options in different formats, and always let your ear lead the way. Functionality is crucial, but sound quality is always the ultimate aim.

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

Audio Recording with Equalizers – 10 Equalizer Modes – Part Ten – Shelf EQ

The Shelf EQ is a vital tool in the art of recording, mixing, and mastering music. It is called a Shelf EQ because it does not taper off at the ends, but remains constant like a shelf until the end of the spectrum. If you use a high Shelf EQ that begins at 10kHz, it will continue in a curve until it reaches a certain point and then remains at that level as far as the upper Frequencies continue. If you are working at a sample rate of 44.1kHz, then the high shelf EQ will continue all the way to 22,050Hz, and a low Shelf EQ will continue all the way to a theoretical 0Hz.

In actuality, it takes roughly 10Hz to reach the edge of a digital wave file, and approximately +/-10dB, but this is practically irrelevant to any audible recording. The Shelf EQ will sound and mostly appear perfectly straight beyond its edge, curve, or slope. A Shelf EQ will normally have Fixed Frequency positions to choose from along with +/- Gain options. As an example, you may have a Program Equalizer with 30Hz, 50Hz, and 100Hz Shelf EQ positions with boost and cut Gain, and you may have high Shelf with 6kHz, 8kHz, 10kHz, 12kHz along with boost and cut Gain. All of these options will extend all the way to the extreme high or low spectrum beyond the starting curve or slope, but the Frequency that is designated will mark the position that the EQ goes from flat to adjusted. In some ways, you could look at a Shelf EQ as being a Bell-Shaped EQ where only one side of the EQ has the Bell, and the other side continues at the height of the Bell. Shelf EQ is not always the exact same slope or curve.

There are some rare cases where a “Q” control that would be used in Band mode, doubles as an adjustable edge for the Shelf EQ as well. In this case, the user is able to not only select the Frequency from which the Shelf will begin processing, but also the shape of the edge Frequency that makes the transition from flat to Shelf. In this case, the user can decide whether the transition is extremely gradual or a quick, sharp transition.

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

Audio Recording with Equalizers – 10 Equalizer Modes – Part Nine – Band or Bell-Shaped EQ

The Band or Bell-Shaped EQ is one of the most important and common EQ modes available today. The Band mode denotes a single location on the EQ spectrum. It begins and ends at the intersection of 0dB Gain. The width of the Band EQ is determined by the “Q” width setting. The Band EQ runs at a distance from its first point, which is the lowest Frequency of the Band, to the second point, the highest Frequency of the Band. When adjusting the Band EQ Gain, it selects the very center point of the Band In most cases. The typical Band EQ is symmetrical, so its central point is selected from minimum to maximum boost and cut Gain points. Typically, Gain can be selected from +/-10dB, but we often see as much as +/-12dB and even +/-16-20dB. The wider the range of Gain, the more potential there is for variability in its response. Sharp “Q” width slopes tend to be steeper and more resonant than smooth narrow shapes and much more than wide “Q” width.

Most Band EQ options are called Bell-Shape EQ. As you might guess, this is named for the height and smooth shape at the peak Gain of the Band EQ. This is usually the most visually consistent at moderate “Q” settings. The more narrow the “Q” setting, the sharper the tip will become. Some Band EQ's are sharper in narrow “Q” and some tend to maintain the same Band shape. Most Band EQ's have a lower range of Gain at their wider settings. The Bell-Shape will be extremely gradual and smooth and the peak levels may be as little as half the amount when they are at the narrowest setting.
It is possible, depending on the intention of design, that the Band EQ is not symmetrical when comparing boost Gain and cut Gain. Some Band EQ's are designed to be a perfect mirror image at positive and negative Gain settings. If these EQ's are plotted on a graph so that you can see all settings and Gain at once, it will look like a perfectly symmetrical oval shape. Other Band EQ's are designed to have a rounder, wider, smoother Bell-Shape when given boost Gain and a sharper, narrower, deeper cut Gain. This is seen as making smooth additive changes that are sonically pleasing and making cuts that are more corrective and affect less of the surrounding Frequencies.

Some Band EQ's are not symmetrical from the edges to the peak or central point. These are rare in comparison, but they can give the user a very unusual and unique creative control that otherwise does not exist. These EQ's tend to have a regular initial distance from point to point, but as Gain is increased beyond a few decibels, there is a curve to the center point, much like a hook or claw. This allows the ability to gently boost or cut a center point and then reduce more from the Frequency just above center. As the point sharpens above the center, there is the increasing ability to cut a very narrow amount of corrective EQ.

When using Band EQ's, I recommend testing out various settings. If the Frequencies are fixed, get to know what it sounds like at boost and cut, and at the steepest settings, to learn if it becomes more subtle and narrow as the Gain is increased or if it remains fairly curved and more audible. If your Band EQ is adjustable in “Q” width, test it out on different material to get used to its affect at different widths. There is always more to the affect of an EQ than the visualization of its shape, so listening is the key to becoming familiar with its individual personality. You will find that you lean more towards some settings over others, and this will help you to develop your personal mixing or mastering style.
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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.