Although each sound engineer intends to record the instruments as clearly as possible and attain a stronger impact (or to use as high-quality samples as possible), his frequency response may be limited at the time in which mixing is achieved. This can happen due to the different monitoring system of the recording studio, the different signal paths, the influence of the sound engineer who recorded, or the musicians. Therefore, when mixing, you may have to “improve” the frequency response of the recorded items. We’ll help you to become the next Sir or Madam-Mix-A lot!

The tool used for this is the audio equalizer, either parametric, graphics, etc. – yet the end result is the same. I personally consider it as the most important and at the same time the most difficult signal processor to use, conceptually as well as its direct applicability.

What is the purpose of equalizing?

  • Make a tool to sound more clearly
  • Enable a tool to sound “bigger”, to have a stronger impact
  • And most importantly, help to combine the elements of the mix, by frequency scrolling of a niche for each of them.

Audio frequency range

Before entering the equalization details, a bracket must be made to observe the main areas in which it can be operated with the equalizer. We will divide the audio spectrum into 6 zones: each with a different impact:

  • Sub-bass: Frequency range between 16 and 60 Hz, including sounds that are not heard in their own way, but they also feel like vibrations (thunder, for example, has a considerably sub-low content); even if they are not constant (maybe only the big drum has a sensible content), they give a sense of power to a mix, but make the mix to be dark and unintelligible, if abusively used.
  • Low: Between 60 and 250Hz, they contain the fundamental instruments of the rhythm (big drum, bass, piano in the lower register: sometimes guitar and so on); equalizing this area can change the toning balance of the mix, making it thinner or fuller; in excess, will make a mix of “constantly bubbling.”
  • Low-mid: the area between 250 and 2000Hz, containing the harmonic first of most of the musical instruments, and may give the sound of “phone” if they are too immersed in the mix (not surprising, considering that 250-2000Hz is close exactly the frequency response of fixed telephony); a strong boost between 500-1000Hz will give a trumpet of instruments, while in the immediately higher octave, it will make them metallic-thin; Using these frequencies excessively will lead to tiring sound. Where’s the caffeine here?
  • High-end: the area between 2 and 4kHz, important for human speech intelligibility, which can be greatly reduced by an excessive boost on overlapping instruments; it’s also a tiring frequency if it’s too strong; by using a small boost around 3000Hz per voice, and a small cut over the overlapping instruments, you can get a much clearer voice, without having to raise your level.
  • High – presence: between 4 and 6kHz are frequencies that are generally responsible for clarity and definition of voices and instruments; a boost in this area may give the impression of approaching listener music, thus a cut in this area will make the element in the mix appear more distant.
  • High – brightness: the frequency range of 6 to 16kHz affects the brilliance, clarity and “air” sensation of the instruments; an overly powerful boost can become disturbing and greatly increase the level of vocal sophistication.

Considering that the “creative” versions of the equalizations as presented above, I will further attack the method by which you use the equalizer to help combine the elements of a mix.

As a starting point, the first consideration should be given to the following concept: the bigger the mixer, less room remains for the other instruments, which have to be smaller to leave it to unfold. Thus, in a loaded mix of instruments, you will be unable to make any of them very large, which would be perfectly possible in a closed arrangement with few tools.

To help mix things better, you can try to follow the next steps – I do not guarantee it will work, and certainly not the only functional method, but it can serve as a guide:

Start with the rhythmic section – drums and bass. The bass should be clear and distinct when overlapped over the drums, without eclipsing them. All rhythmic elements should be heard distinctly, try the following:

  • Make sure you do not have two boosts on the same frequency on any of the elements; if there are, move them one way in one direction to each other, enough to achieve separation without losing their effect (desirable, I think).
  • If a tool has a cut at a certain frequency, you can try a boost on a tool that occupies roughly the same area (big drum/bass guitar, for example).

Add the most important element of the mix (voice in general) and repeat the steps above.

Enter the rest of the items, taking care not to “step over” over the rhythm and voice section.

The idea is that each instrument should be clearly heard, and the best method is to have each place in the frequency band.

After you have worked the instruments frequently to avoid intersecting, it is perfectly possible that they will sound very bad once they are put in solo; it’s not a problem, just the context counts as it sounds.

Several “rules” of equalization:

  • If an element does not sound distinct enough, try cutting at the frequency around 250Hz.
  • If it sounds nasal, you can try to reduce it from the frequency range of roughly 500Hz.
  • Apply a frequency cut if you want something to sound better, or blend more cohesively with the rest of the elements.
  • Apply a boost if you want to sound interesting or differently.
  • You have no boost if that frequency does not exist from the start (7-16kHz on the bass guitar, for example, or 40Hz per voice).

The equalization concept was first applied for correcting the frequency response of telephone lines using passive circuits before the invention of electronic amplification. Initially, equalization was used to “compensate” the unequal frequency response in the audio band of an electrical system by applying a filter having the opposite frequency response, thus restoring the fidelity of the transmission. An ideal frequency response would be linear, ie the audio chain through which sound passes from its recording until its playback does not affect the sound spectrum. Hence the term “equalization.”

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