How To Use A Compressor On Vocals

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Let me tell you a little secret that most sound engineer will agree on, The best compressor for vocals is a good vocalist! But since we are not talking about vocalists here, I will give you some of what I know about compressing vocals and show you a few of the compressor plugins I work with.

The more I know about compressors the more I do less with them. When we’re beginners, we overdo pretty much everything. I also like to over compress from time to time and use it as an added effect to a vocals track. But it shouldn’t be our default. 

The Hammer

If EQ’s are the sound engineer’s sculpting tool, then compressors are the hammers! Sometimes a good hammer can take a vocal from “ok” to pretty much amazing. Even though I always say don’t over compress anything, the only way to learn what a compressor really does is to over compress things. It’s like putting your hand on the stove to learn that it’s hot and getting to the conclusion you don’t want to do it again. 

What Really Is  A Compressor?

When I was in sound engineering school, I remember my teacher’s (The great Yoram Vazan) first words: “A compressor is only an over glorified volume fader”. This got stuck in my brain and every time I work with a compressor I think about the statement and it helps to remind me of the most basic things about it.

Compressor – How Does It Work?

Don’t worry, I’m not going to give you the whole preach about the basics that bloggers usually do. All we need to know for now is that a compressor receives a signal and run it thru a few parameters when the end result is a dynamically reduced representation of the source. The compressor’s job is to compress the dynamic range of the signal. That means that it controls the channel’s volume based on a few pre-defined rules.

Compressor Features

These are the most basic features you’ll find in most compressors. Some of them will have more, some less but these are the most basic ones:

Input – The level of input gain goes into the compressor.

Output – The level of output gain goes out of the compressor

Attack – Determines how quick the compressor starts compressing since the signal goes above the threshold.

Release – Determines how quick the compressor stops compressing once the signal goes below the threshold.

Ratio – Determines how many compression will be applied to the signal once it goes over the threshold.

Threshold – Determines the specific spot on the level meter that tells the compressor when to start compressing. In some compressors, the Threshold is determined by the input Knob

Types Of Compressors

All of these compressors do practically the same but each in its own unique way. I won’t get too technical on you but I’ll give you the highlights of each type and go over their sound characteristics.

Optical compressors – (Opto Compressor) These basically work with an electrical light element that determines how much of the signal will get compressed. These have a smooth sound, slow compression and natural sounding behavior. The optical compressors usually shine on vocal tracks. With their slow features and a smooth overall sound, they’ll sound good on almost any vocal source. A good example of an optical compressor is the legendary Teletronix LA-2A, which had almost too many virtual plugin versions. Two of my favorite virtual replicas are made by Universal Audio and Waves. Use an Opto compressor if you want your vocals to sound smooth and natural.

FET Compressors – (Field-Effect Transistor) This is a compressor that uses transistors. Its characteristics are the opposite to the Opto compressor. It’s considered to be fast, flexible, colorful and punchy. The FET compressors are used a lot to control drums and any instrument with fast transients. With vocals, the FET compressor allows very accurate results due to its very fast attack and release. The most famous FET compressor is the classic Universal audio 1176 which a lot of plugins today are modeled after. Use this type of compressors if you need your vocal to be 100% dynamically controlled and full of character.

VCA Compressors – (Voltage Controlled Amplifier) This compressor is based on relatively modern technology. As with the FET compressors, it also gives you control over the attack, release and ratio parameters. The VCA is a versatile animal that can tackle pretty much everything. From shaping a snare sound to controlling a very dynamic vocal. The most famous VCA compressor is the mighty SSL G series Console Bus Compressor which is responsible for a lot of timeless recordings. These behave pretty much like FET compressors but to me, they sound a little less aggressive. So I use them when I want something to be very controlled and without too much coloration and harmonic distortion. This is just how I perceive it.

Variable Mu Compressors – These are tube based compressors. We all know tubes are characterized by warm, slow and colorful sound. This is a very old technology that was first introduced in the 50s. These compressors are commonly used for bus compression although it’s been used for pretty much every sound source we can think of. From breathing new life into electric guitars, squashing a vocal or tightening a whole mix. The most famous tube Compressor is the legendary Fairchild 670 which is maybe the most expensive piece of audio gear today. If you want coloration and vibe, this is the way to go. Most of the Fairchild emulations I had the chance to work with, sounded amazing. So it doesn’t really matter which one you use to give your vocals those majestic colors.

How To Use A Compressor On Vocals

What To Do When I First Put A Compressor On The Vocal Track?

I assume that you already know what each and every parameter does, so when I use the known terms you know exactly what I mean. Now, if you’re looking for rules and guidelines in that particular subject, to be honest, there are none. All I can do is tell you what I personally do and look for when I first put a compressor on my vocal channel. So the first thing I look for in a compressor is the initial introducing of the “character” and how it affects the vocal. Every compressor doesn’t matter if it’s a plugin or a hardware compressor, has a “sound”. Especially the ones which are modeled after the old and legendary hardware units. So I’ll try to give you a basic starting point.

1. LA2AWaves LA2A CompressorIf it’s a classic LA2A for example, I first lower the output and increase the input to hit the compression circuit harder to be able to point out the effect for myself. If I like the effect, I keep playing with it until I hit a sweet spot. With the LA2A most of the parameters are controlled by the level of the source going into the circuit so it’s relatively simple, you just play with it until you reach a sweet spot. 

2. 1176 With FET type compressors, such as the 1176 I start with lowering the output again, increasing the ratio to a high enough spot, and the input until it shows compression on the VU meter. Then I play with the attack and release knowing that I’m controlling the dynamic envelope of the vocal. It’s very important to learn what each an every parameter does so you can look for the change in the right places as you’re playing with the compressor.

3. Ratio – With LA2A type compressors you don’t have a separate ratio knob. You change the ratio by simply increasing the input gain into the circuit. With a 1176 type compressors you start with increasing the ratio. 5:1 is good as a starting point. Always look on the gain reduction meter. This whole thing is just pointing out the obvious because a compressor is a simple device, but it’s important to know what you’re doing because it’s so easy to take your beautiful vocal recording and turn it into pure shit, with a bad compression setup.

4. Gain Staging – Remember, gain staging is one of the most critical parameters for getting a good output out of any audio device. Make sure your input signal sits in a good place around the 75% more or less. This will put you in a safe place, far enough from the noise floor and not too close to the algorithm’s level ceiling where it starts digitally distorting, and we all know how a digital distortion sounds.

In the early years, I used to over think every little change on the compressor. Today the whole process of compressing vocals is much more intuitive and done almost subconsciously while I hover with the mouse over the whole plugin to find it’s sweet spot. All this will come in time as you gain more and more experience.

One Channel, 3 Compressors

I usually use more than one compressor on the main vocal channel. To be exact, I use 2 compressors with a limiter at the end of the chain. So the first compressor handles the heavy duty. The second one is there to round the edges and sometimes to add another color to make the vocal sound a little more 3D and harmonically interesting. The last compressor I use on a vocal channel is actually a limiter. I love controlled vocal channels. This still doesn’t say I compress too much. It only helps me to achieve what I hear in my mind without sounding too processed. This is usually followed by tons of meticulously crafted lines of automation all across the channel.

Digital Compressor Plugins

There are those plugin compressors that are not modeled on any hardware device. Some of them are really good and although digital in nature, they are not lacking on mojo. 

These are some of my favorite digital compressor plugins:

Waves C1 Compressor

I absolutely LOVE this compressor, it sounds great, and it has tons of character. There’s something special in how it handles transients. Very snappy and accurate. as far as dynamics go, I can get exactly what I need with only this compressor alone. I like it on side chain applications. For example, compressing a bass guitar channel that’s being triggered by the kick drum.

Waves Renaissance Compressor

Another amazing digital compressor from Waves?? hey, they’re great, what can I say? This one is even better, visually. Its design is pure genius. The gain reduction meter is brilliant, and it shows me exactly what I hear, which is amazing and not that common. It has a few modes, Electro, Warm and Manual. Each one of them makes the compressor sound a little different.

McDSP Compressor Bank CB303

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This is an ol’ trusty dog. It’s a part of a pack of three different compressors that sound so good! I’m proud to tell you I have a lot of mixes based almost entirely on McDSP plugins. Compressor Bank is one of the most impressive digital compressors I’ve ever laid a mouse on. With all the newest plugins that are coming out each year, I can’t seem to give this old dog up. If there is such a thing as “Classic vintage plugin”, this is definitely one of the few ageless plugins out there. These days its price is so low (No justice) it’s a no-brainer. Just go out and get it!

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