Posted on 17. Mar, 2016 by Daniel Duskin (Record Producer, Mixing & Mastering Engineer) in EQ, Mastering, Mixing
Yesterday I discussed the differences between additive and subtractive EQ in a mix or master. You can read that article here.
Today I will discuss what kinds of EQ’s to use for each type of processing for professional results. If you are unsure which to use, you might want to check out yesterdays article first.
Choosing The Best Tool For Frequency Reduction
When it comes to subtractive EQ, the goal is to reduce or remove a problematic frequency range. Because frequency reduction is a destructive process, it can be valuable to use tools that remove no more than what you are trying to remove without added distortion.
There are at least three types of EQ filters that can help make sure you aren’t reducing or removing any more than what you are trying to reduce or remove.
1. Notch Filter
The first kind of EQ is simply a narrow bandwidth—or a narrow Q—filter type. By using a parametric equalizer with a bandwidth—or “Q”—option, you will have the option to narrow the range that you are cutting, resulting in what is often called a “notch filter”. With this type of filter you can remove the unwanted tonality while preserving far more of everything else. Generally speaking, subtractive EQ often sounds best (and solves mix problems more effectively) when it has a fairly narrow bandwidth (or Q).
2. Digital EQ
The second kind of EQ is digital equalization. In the modern age digital EQ’s are even more common than analog, but it’s still important to take note of these differences. A well designed digital EQ should add less artifacts than analog equalization. While the added artifacts of analog EQ can sound pleasing, when the goal is reducing a frequency range you will need something more surgical than colorful.
3. Linear Phase
The third type of EQ filter that I would like to mention is the linear phase EQ filter. A well designed linear phase EQ shouldn’t add any significant comb-filtering, resonant peaks, or other audible distortion while reducing frequency ranges, making it ideal for subtractive EQ filtering and notching.
Choosing The Best Tool For Frequency Boosting
When boosting frequency ranges (additive EQ), it’s usually more acceptable to color the sound, because the goal is usually to add and enhance. Since non-linear phase EQ’s can add resonant peaks (with extreme settings), these peak resonances can contribute as part of the color you are imparting on that channel. This is often ideal while boosting.
There are at least four kinds of EQ filters that can be useful tools for frequency boosting, and each one has a very specific sound.
1. Digital EQ – or Transparent Analog EQ
When in doubt, this is the safest option. It’s a no-risk solution to your frequency boosting needs, and often sounds the best as well. In the plugin world, EQ’s that fall into this category include virtually every stock EQ channel strip that’s part of every DAW software. A fantastic plugin alternative to your stock channel strip would be the Sonnox (formerly Sony) Oxford EQ.
When in doubt, the digital EQ that came stock with your DAW is probably the best option.
2. Analog EQ – or Modeled Analog Plug-In
Analog equalization, or even modeled analog EQ plugins are common favorites for frequency boosting—and for a good reason. Classic analog EQ has a sound—a color—that we love, which can be oh so very sweet for boosting. Keep in mind that they all sound different, so you might want to try a few.
3. Harmonic Excitation
This technique was all the rage for a short while in the late 70′s and early 80′s, after companies like Aphex introduced their Aural Exciter. A few years later the pendulum swung the other way, and these devices were quickly ridiculed. If used on sounds that can handle a little added bite, and if properly used with care, these processors can do wonders—in a good way. I’ll try to write an article on the benefits of these processors, how they are misunderstood, and how they’ve been misused.
Harmonic excitation can quickly sound harsh and unpleasant, so these tools should be used with caution. Yet, when in the right hands, they can sound fantastic!
Harmonic excitation often works wonders on kick drum, toms, and bass guitar. On the other hand, applying harmonic excitation to vocals, acoustic guitar, or cymbals (especially cymbals) can be the quickest path to an extremely unpleasant scratchy musical destruction.
4. Dynamic Excitation
This is the latest technique in frequency excitation that gained popularity in the last 10 years. Instead of statically boosting a frequency range by any given amount, dynamic exciters boost these frequencies by varied amounts based on the input signal. This can be a phenomenal option for increasing clarity to an otherwise dull recording.
It can perceptively sound as if the boost is almost coming from the source instrument itself, instead of simply boosting a frequency range in post—this experience can actually be rather stunning.
With that said, I wouldn’t say that dynamic excitation sounds better than normal range boosting with a good EQ—I would rather say that dynamic excitation can sound best when nothing else does the trick.
Summing Up — Best Practices
If you need to cut a frequency range:
Digital EQ’s are best, Linear Phase is even better, and start by keeping your bandwidth—or “Q”—settings very narrow (notch filter).
If you need to boost a frequency range:
Start with your stock DAW channel strip EQ. If you want more color, reach for analog—or modeled analog. If you need something more drastic, you can experiment with harmonic or dynamic excitation, but proceed with caution.
Finally — In Closing:
If you try something else and it sounds better, do that! Just do me the favor and post your findings in the comment section below