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 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 unable 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 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.
Nebula (N3 and N4 Commercial) Program Libraries