Professional vocalists are trained to sing at a consistent level. Through experience, they also learn how to listen and blend when singing together. Since most church vocalists are not trained professionals, we can improve the sound of the vocals in our audio mix by adding compression to each vocal channel.
Compression is one of those things that takes time and energy to learn. It can be your best friend or your worst enemy. One doesn't learn how to use compression simply by understanding what all the knobs do. I involves art and science. It takes time. However, to experiment you must understand all of the parts. So we will look at what the compressor does and then some techniques and ways to learn how to set compression.
Threshold
A Threshhold controls where the compressor starts to work. The dial usually ranges from at least -20 to positive 10. When you set this knob to a specific decibel you are essentially saying “start compressing here.”
Ratio
The Ratio knob is what happens once the Threshold decibel is engaged. The Ratio typically has numbers on it that look like this 2:1 or 4:1 etc. If you select 2:1, every time your input signal exceeds the threshold by two decibels, the compressor will only allow a one-decibel (1 dB) increase. Likewise when set at 4:1 (or 4 to one) the compressor will only allow a 1 dB increase for every four decibels that exceed the threshold.
Attack
The Attack control is used to tell the compressor when to start engaging in milliseconds (MS). The control know tells it how fast and how slow to start. It is important that you spend some time adjusting this control because you do not want the compressor to kick in too fast or wait too long to kick in. If it does either of those things, the effect is essentially useless.
Remember that compression is not a “set it and forget it” application.
Release
The Release function controls how long the compressor reduces the gain of the signal. Like the Attach control, Release is also measured in MS (or milliseconds). Also, just like the Attack function, it's important to spend some time to dial this in correctly. For instance, if a vocal starts compressing because the singer hits one high note that is louder but the Release is set to wait for half a second it may lower the vocal too much on the next note.
Make Up Gain
Make up gain is there to help you out. When you start compressing you may loose a little bit of gain, so you use this function to give you a touch more volume. It is important to note that if you are receiving a lot of gain reduction it is most likely that you need to loosen the compression before giving a microphone six or seven dB of make up gain.
Gain Reduction Meter
Most compressors have four or five little red lights on them with negative numbers beside them. This is your gain reduction meter. This is showing you how many decibels your compressor is reducing the signal. These lights are very helpful and will help you navigate each signal as you set the compression.
How to Set Your Compression
The first thing you have to remember is that it is not about where your knobs are set, it is about what the gain reduction lights are telling you. Settings will change. That is a promise. However, the only steadfast friend you have is knowing how much your compressor is working.
For this article we will give you a few tips on how to compress a vocal. There are many videos and tutorial on learning how to compress drums or instruments online. Just Google it. For example: Electric guitar compression settings.
Vocal compression can be your biggest help in getting a good mix in your church --- if it is done right.
Vocal compression can be your biggest help in getting a good mix in your church --- if it is done right. The first thing you want to do is adjust your threshold as the person is singing until you see that they are starting to tap the gain reduction lights. If your compressor doesn't have a gain reduction light I would recommend buying a different compressor. See that it is starting to hit in the threshold when the singer starts to sing harder.
The second thing you want to do is make sure that the Ratio control is taking off the appropriate amount of gain. If as soon as your compressor starts to reduce gain (refer to the lights) it is more than 2 dB then that probably means your Ratio is too hot. As a general rule of thumb (this is my opinion and preference and I realize others may differ with me), I would never allow my Ratio to be more than a 3:1 on a vocal. I just don't want to ever see more than 6 dB come off of a vocal.
As you are finishing up, make sure that your Attack isn't keeping your compressor from kicking in too late. The same with the Release. Make sure it isn't making your vocal sound goofy. You will have to adjust these two controls for every vocalist. Use your Make Up Gain control as needed, but use it as sparingly as possible.
Generally faster Attack and Release times work well with vocalists. You may have a very dynamic vocalist, someone who transitions from singing softly to loudly very quickly. In this scenario the goal is to get the loud sections of singing to sound more even with the soft sections. With fast Attack and Release times (and the properly set Threshold), the compressor will engage at the appropriate time and quickly even out those louder peaks in the performance while letting the softer sections remain uncompressed thus evening out the vocal dynamics.
Be careful to listen to how your compressor changes the sound of your vocal. Many times a compressor can add a warmth or darkness. This can be a welcomed change to your vocal sound or you may find that after compressing appropriately you will need to apply some more EQ. Use your own judgment as every singer will be a bit different.
Finally remember that compression is not a “set it and forget it” application. How someone sings in rehearsal is not necessarily how they will sing during service. The harder a person sings, the more signal there will be going into the compressor. If you don't adjust your threshold accordingly, then you will get additional unintended compression."
Special thanks to Nolan Rossi who assisted with this article.
