EQ Overview and Introduction

In the next series of blog posts, I’m going to go through EQ, or equalization. I will talk about why we use it, and when and how to use it. I think EQ is easier to understand than compression (my last series of blog posts), but when I see EQs added by young producers and engineers, I realize they are just as lost using EQ as a compressor. Partly, this is because they don’t understand frequencies.

In this blog I am going to start with an overview. I think to understand EQ and use it properly, one must understand frequencies, our ear’s perception to frequencies, the frequency spectrum (or range), and frequency specifics of individual instruments.

To start with, the ear hears 20 Hz to 20,000 Hz (or 20 kHz). This is, of course, ideal, but starts to become less (mostly on the high end), soon after we’re born. If you’re serious about a career in music, it would serve you well to NOT listen to loud sources for very long. Personally, I wear ear protection when using my leaf blower and shop vac!

If you think about an acoustic piano, the lowest note is A0, 27.50 Hz, and the highest note is C8, 4186 Hz. I bring this up because I think it helps us equate pitch with frequency. Next chance you get, go play specific notes on a piano (acoustic or digital), and then consult a chart as to the frequency of that note. For instance “middle” C is 262 Hz. A440 (the A just above middle C) is 440 Hz.

Do you know what an octave is? An octave, at least on a piano, is from, say, middle C up or down to the next C. This happens to be 8 white keys, thus octave. Using octaves, the frequency either doubles (up an octave) or halves (down an octave). So middle C (C4), 262 Hz, up an octave goes to C5, 523 Hz. (Technically, C4 is 261.63 and C5 is 523.25 Hz.) The A above middle C, A4 is 440 Hz. Up an octave is 880, down an octave is 220. Down another octave is 110, then 55, then 27.50, the lowest note on the piano. All instruments, of course, can go up or down octaves at a time.

The lowest note on a guitar is E2, 82 Hz. Guess what a bass guitar’s lowest note is? One octave down, 41 Hz. This is important. For one reason, when EQing either of these instruments, I know there is no useable information below those frequencies, so I will use a high pass filter set just below those frequencies. This helps to clean up the sound of these instruments, make them less muddy.

The frequency spectrum (20 Hz – 20 kHz) is broken into ten octaves:

1. 20 – 40
2. 40 – 80
3. 80 – 160
4. 160 – 320
5. 320 – 640
6. 640 – 1280
7. 1280 – 2560
8. 2560 = 5120
9. 5120 – 10, 240
10. 10,240 – 20, 480

So, the lowest note on a bass guitar, 41 Hz is in octave 2; lowest guitar string is octave 3; middle C on piano is octave 4; A440 is in octave 5. Where do vocals sit? Fullness, for example, is 140 – 440, octave 3 to 5.

A different and more effective way to think about the frequency range is to break it up into five broader ranges:

1. 20 – 100         Bass (Sub Bass)
2. 100 – 500       Mid Bass (Upper Bass)
3. 500 – 2 kHz   Mid Range
4. 2 k – 8 kHz    Upper Mid Range
5. 8 k – 20 kHz  High (Treble)

Bass:                           Depth, Power, Thump

Upper Bass:              Warmth, Body, Fullness

Mid Range:               Bang, Nasality, Horn-like, Fullness of high notes

Upper Mid Range:  Presence, Edge, Punch, Brightness, Definition, Excitement

Treble:                        Brilliance, Sizzle, Treble, Crispness, Airiness, Breathiness

As example, electric guitar has too much “edge,” cut in the upper mid region. Vocal sounds a little nasal, cut in mid range area. The overall track needs more power and punch, boost bass region.

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To go deeper, the human ear (and mind) hears and perceives sound differently at different frequencies and levels of loudness. Generally speaking, we are more sensitive to mid range and upper mid range frequencies. The ear is less sensitive to low frequencies at lower volumes, and slightly less sensitive to higher frequencies compared to mid range frequencies at the same volume. Being more sensitive means we hear it easier and more readily.

Another way to say this is at low listening volume, mid range frequencies sound more prominent, while the low and high frequency ranges seem to fall into the background. Conversely, at high listening volumes, the lows and highs sound more prominent, while the mid range seems comparatively softer. Confusing? Yes. But extremely important to understand.

To illustrate – Let’s say you’re working on the EQ of a mix, and as you listen back at low levels, you think the lows and highs could use a boost. So you boost them, and it sounds great. The next day you listen back at a high volume, and notice the lows and highs are too loud, so you cut them back down some. Sound familiar? This is the Equal Loudness Contour effect.

There are two different charts one could consult to dig deeper into this important, albeit nerdy and technical subject – Fletcher-Munson Curves and Equal Loudness Contour. There are many articles available online regarding these two subjects, so I will not get into them. BUT, it is extremely important to realize how important these affect your work as an audio professional!

I went a little more in depth than normal in this post, but I hope it helps you to understand what is involved when learning to become an successful producer or audio engineer.

Peace –

And, HEY! Make it a GREAT day!!

Tim

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Compression Dos & Don’ts

To wrap things up regarding compressors, I will offer 3 Dos and Don’ts as my final word for now. These are things to always keep in mind when working with compressors. Some may have been previously stated in an earlier blog post.

DO          Avoid using extreme settings to begin with, if you are just trying to control the dynamics.

DON’T   Add compression to every channel by default. Start off with minimal compression, and carefully choose where to add compressors.

DO         Experiment with different types of compressors – hardware and software. There can be differences in how they sound. Compressors can and do sometimes sound different from one another.

DON’T  Forget to bypass the compressor occasionally while setting to check the results.

DO         Remember to balance the output gain so the level doesn’t change when engaged and bypassed. This way you can accurately compare before and after. Also, typically compression is added AFTER the mix has been balanced. So you don’t want to alter levels with either compression or EQ.

DON’T  Be afraid to experiment. Some of the greatest sounds in the history of recorded music came from misused and abused compressors.

Compressors – What is the Knee and What does it do?

As you get better with compressors, you will start playing with other knobs and features. One of these is the knee. The knee refers to when and how the ratio starts to change when the compressor starts to take effect. A ‘hard knee’ means the compression becomes immediately active as soon as the input signal hits the threshold. A ‘soft knee’ means the compression becomes audible more gradually. A ‘soft knee’ also means that gentle compression starts happening further below the threshold. Another way to say this is it starts acting before the signal actuall reaches the threshold setting.

Both hard- and soft-knee compression have their uses; two examples: if you want to squash a signal’s transients quickly, you’ll want hard knee compression. If you want to use a compressor to gently glue a mix together by tightening up transients, you’ll want a soft-knee compressor.

Lastly, if you have a compressor, like the Dyn3 Compressor/limiter which comes free with Pro Tools, look at the picture of the knee. It actually looks like a human knee!

As always – I hope this helps!

And…. HEY! Make it a great day!

Tim

Compressors 103 – Going deeper

Today I’m going to go a little deeper into how compressors work. But first, I want you to do an experiment. This experiment will allow you to SEE what a compressor does. When I did this, things started to become a lot clearer for me. We have to listen differently when it comes to compressors. We are not listening for frequency, we are listening to dynamic changes (amplitude, loudness).

For this experiment it would be better to use a bass track. The reason for this is one, we ALWAYS use a compressor on a bass track and two, the reasons to use a compressor on a bass track is because we want to control the initial attack of a note and lengthen the sustain of the notes, as they fade out quickly. Try to use a track that has a regular-type bass line, not one that is super busy.

1. Find a bass track (or create one using a VI).  If a virtual instrument is used, use one that emulates a real bass guitar, not something like a synth bass. What is needed is a sound whose initial attack is strong (loud) and whose note decays after the initial onset of the note, like a real bass. Also, the track will need to be printed. For this test to work we need an audio clip, not a MIDI clip.
2. Put a compressor on the bass audio track.
3. Set the ratio to something higher, i.e. 6:1. Set a fast attack, i.e. 3 ms; fast release, i.e. 18 ms.
4. Lower the threshold until the meter shows roughly 8 dB of gain reduction. Then add some makeup gain. Set this to the amount being reduced. If the gain reduction meter shows 8 dB of reduction, set makeup gain to 8 dB. This way the volume remains the same.

What you should start to notice is that the initial attack of the notes (when the player first strikes the notes) no longer punches. Now the dynamics are a little flatter, smoothed out. The second thing you should notice is that the notes are more sustained. You will no longer hear the decay, but a nice solid note that holds out for it’s full duration of note value (i.e. quarter note, half note, etc.)

NOW, print the track again with the compressor engaged. What you should have are two printed bass tracks. One without compression and one with compression. Look at the differences between the two. The first track has a pronounced attack with high amplitude and fast decay. The second, the initial punch is now all or mostly reduced and the sustain of the note stays strong longer. Below is a picture of what this should look like. 

I have done exactly that here. I used an Instrument track with Trillian Bass module – played a bass line – printed it – ran compressor with 6:1, 3 ms attack, 18 ms release, 8 dB gain reduction, and 8 dB make up gain. I think this helps to drive home what a compressors job is. In this example my goal with the compressor was to lessen the attack and give it more sustain. If you want to see what the compressor does even more obvious than this, use the fastest attack possible, with 8:1 ratio, with a lower threshold for more gain reduction (10 dB).

I hope this helps – it did for me! Next time I will start to go into specific parts of a compressor, i.e. threshold, knee, attack, release, etc.

As always – HEY! Make it a great day!
Tim