EQualizing 101

Robbikal Adlim Saturday, March 16, 2013

Basic EQ Theory

To understand EQ is to understand limits. It is in it's essence an understanding 
 that allows the whole (the song) to sound bigger by making the elements 
(the tracks) sound smaller, more narrow, and dare I say it in the world of 
phattness, thinner. This is because the audio bandwidth is itself limited. There is 
only so much space you have and if you fill it up with frequencies that overlap 
and conflict, you will not be able to hear the music through the sound. Stated 
positively, if you carve out a distinct sonic space for your instruments, you will 
hear each more clearly. That is the basic point and essential understanding that 
goes into developing a mix. Always remember, it is not how things sound in 
isolation that matters, it's how well they sound in the mix.

The Audio Bandwidth=20Hz to 20kHz

Like it or not, this is all you have to work with as you put your song together. Every element has to "fit" into this sonic space. Note the above example coming straight out of Cubase with no processing. Its got an awesome low bass synth track from Atmosphere. Look at that 30hz bump! Lets solo it and look in another display from Waves (below).
As you see there is low frequency energy extending way below what we can hear. This energy will rob the song of audible bass and make speakers work very hard for something that has no benefit. So lets fix it by applying a "bass rolloff"

With Waves Linear phase Bass EQ we'll apply a rather steep resonant rolloff where the bass will peak where I want it around 70 Hz and then get out of the way quick.

As you see the result is dramatically conveyed in the screen. I've removed the bass you can't hear and also cut a little bit of the "mud frequencies" around 250Hz.

There is only one problem. It does not sound as good as it did. It is not as deep, 
or powerful.

Mr. Newb, who has finally recovered from his near-lobotomy shouts out. 
"You should have left it, Tweek, it sounded better before, you've turned a great 
bass into a wimply thang." Perhaps so, perhaps not. I still have to add a kick, 
more deep synths, a ton of drums and percussion and some vinyl brass hits. 
The point is that I now have control of the bass and i can move that peak from 
75hz down to 60Hz anytime I want. I can add a kick that extends lower and 
peaks at 50HZ and you'll feel it. The bass patch no longer controls the song and 
where things have to go. Also we must keep in mind that 50Hz is a very "boomy" 
frequency that will make many speakers distort and ruin the rest of the track. 
While 50Hz sounds great on my Mackie 824's, I can guarantee you it does not so 
so tight on other speakers.

The Theory of Masking

Tweak reaches into his box of manuals he always carries and pulls out a very scary looking Alien mask. You think the lobotomy thing was bad, now you are in for it. The Pros in the back start pointing to their watches and emit a sullen groan, "here he goes again"
The masked Tweak turns towards the pros. "Alright you guys, get out!"
"But T-t-t-tweak, we were just wondering how long this is going to go, c'mon man!"
"I said, get OUT!"
The pros start shifting around and start looking at each other. I mean is he kidding or what!

When one masks anything you can't tell what it really is and its the same with
 audio. When you have 2 or more parts sharing the same sonic space you will only hear the 
loudest, the other sounds will weaken to the point where you can't really tell what they are. 
Some examples: A Bass that masks the kick will make a great kick sound like its not there. 
A full spectrum distorted guitar will make words incomprehensible. A bad vocal track will mask 
a great sounding instrumental mix. 2 guitars using a similar tone will make a jangly mess and you 
can't tell what either is playing.

The keyboard player starts scowling at the guitarist, who has just ripped off his shirt and put his amp on volume 9. So the keyboard player puts his amp up to 10. Your vocalist is getting all peeved because she can't hear herself now so she starts screaming instead of singing and its o-my-god-awful. Now even the drummer can't hear himself so he starts banging on the crash cymbal. Neighbors complain, police arrive and you find out you are going to jail for some unpaid traffic ticket. That is masking at work.

Making the Mix "Sit Right"

Waves Native Platinum Bundle (Macintosh and Windows)
The solution to masking problems usually involve a combination of 4 Possibilities.
1. Fix with panning. By moving things left or right you can cure many masking problems. But not all. You can't move the kick of bass or vocal too far from the center or the whole mix gets lopsided. But you can move rhythm guitars, synths and percussion way off center and it helps.
2. Fix with EQ. Bass removal from your tracks does wonders. At minimum put a low cut (high pass) filter on every track except the kick and bass (which get their own more extensive treatment).
3. Fix by dropping one instrument for part of the mix so both the mask and masked are not playing simultaneously.
4. Removing the track entirely.

Once you get your mix sitting right then you can get to work on fattening it up by adding compression and maybe putting back some of the frequencies you removed with EQ. The difference is now you have control over your mix.

EQ Production Tips

OK, it's time to go out there. Here's a few little production secrets, your reward for coming so far.

1. The Brain, Perception, and the Mystery of the Missing Fundamental  

The "fundamental" is the loudest part of any musical note. Remember that. See, every note made by any instrument contains a fundamental and overtones (other frequencies). We identify pitch by the fundamental, and identify the instrument by its unique series of harmonics (overtones, other frequencies).
How many of us have heard a deep hip hop groove where everyone is nodding their heads then suddenly the producer drops a note. The sheer inertia in our brains keeps us on the beat and we replace the missing beat in our heads. This is a cool effect. And it works on other instruments too. One theory has it that you can almost totally remove the fundamental once it has been established and only keep the overtones. Establish your groove then back it off with automated EQ, giving other stuff a chance to breath. Come around to a short section after the chorus and put it back.

2. Vocal "telephone" effects

One of my favorites for vocals.  Use a parametric EQ and cut away a big chunk of the low and lower mids.  I usually go from zero to 700-900 hz cut away.  I will also roll off the high end sharply.  This just leaves the mids and upper mids.  Squeeze those filters to shrink the bandwidth of what you hear till its tasty.  Best not to boost very much in the upper mids; it gets harsh if you are not careful.  This effect makes vocals more intelligible while it shrinks their sonic space, 
letting other instruments stay on top as well.  You can also get this effect with guitar 
distortion and bit crushing, if used lightly

3. Creating a worldly color. 

Here you put an eq after a reverb and only let a narrow bandwidth through, starting with lower mids and ending with upper mids.  Use in a very subtle way, just a shadow behind the drums or lead vocal.  Use a short "room" reverb.  

 4. Spacey vocal delay

At the last word of a verse or chorus, automate a send to slam the vocal into a digital delay and let it run away with feedback till it self-oscillates. Normally this would overtake and ruin the whole mix.  So put on a limiter and make sure the oscillation can only be heard at a low level, no matter how out of control it gets.  Now after the limiter put that telephone eq or similar on the bus. In the end its sound like an ethereal reverb.   When you are done with the effect automate it to shut off or bypass. 

5. Playing with resonant peaks.

Use a narrow parametric reverb that can sweep the whole audio bandwidth. Extremely narrow "Q" factor. The slope of the eq curve looks like a narrow pin.  Now automate a sweep over some audio material.  You can make effects with your software parametrics that rival analog filters in synthesizers.  Use your automation tools to sweep up and down the audio bandwidth.  Good for trance like basslines.  You can experiment with 2 bands going in opposite directions, perhaps a wide band cut and an narrow band boost.  

6. Bass Roll-off. 

Its a good practice to try a roll off on every track and don't be afraid to push the eq to cut off or roll off everything under 500hz.  If it sounds "wrong" then gradually dial some bass back in till it sounds right.  The idea is to cut away as much as possible.  This will give you a solid low end for your kicks and bass. Tracks that may benefit from a roll off are guitars and cymbals. There may be a gentle bass roll off applied to the whole  mix.  But to minimize the need to do this, get rid of unwanted bass at the track level.  

7. Better definition on Electric Bass

Newbs tend to think if they boost the bass band of a bass it will sound "more like a bass".  However, boosting the bass band easily can overpower the mix and make the bass sound indistinct at the same time.  The way out here is to leave the bass band alone or actually roll some of it off and boost a region 4-5khz by a few db.  By boosting the treble part of the bass it makes the timbre more identifiable
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