Church Sound: The Art (And Necessity) Of Compression

Ratio. This one is a relatively simple concept. The ratio simply says for every “X” dB the source goes up in volume, the compressor will only let the output go up “Y” dB.

For example, if you set a vocal mic with a 3:1 ratio, for every 3 dB the vocal increases coming into the board, the output will only increase 1 dB.

You can think of the ratio as setting the size potential of the source. If you want it to be able to go bigger, you can leave your ratio smaller. If you want it to stay a little smaller, or perhaps be more under control, you can set your ratio higher.

I tend to start with a ratio of 3:1 for most vocals and guitars, and often times I will go 4:1 or even 5:1 on drums or very dynamic guitars.

My preference is to start low and if you need more compression (less range) you can always increase the ratio. The reason it is my preference is simply this, I don’t want to take away any more control from the musicians than is absolutely necessary to make the mix work well.

If I start it at 5:1 when 3:1 will do and don’t adjust it down, I may be holding that source back. If I start low and it’s still too big, I can easily adjust my ratio up.

Attack. The attack is how quickly the compressor responds to the volume change. A slower attack will sound a little smoother, rounding out the sound of your source a little bit and in essence making it sound a little “fatter.”

A slower attack will generally be less noticeable which can be good for vocals and some thin or scratchy guitars. Setting your attack to a faster setting can be great for instruments such as drums or any other very aggressive instruments. A faster attack will give an instrument more of an aggressive, pumping feel, and potentially bring out more of the high end edginess. The ultimate decider on where to set this is by listening. I tend to set vocals a little slower, guitars in the middle, and drums faster to start.

From there, if you need a little more aggressiveness or “snap,” speed up the attack, and if it needs to be a little smoother or fuller, slow it down. As in all things with sound, let what you hear guide your settings and adjust until you’re happy.

Release. The release is the back side of the attack, and sets how quickly you want to release the compression once that loud burst is over. As with the attack, a slower release will sound smoother and less noticeable, but it could end up taking some of the aggressiveness out of aggressive instruments by compressing them when they don’t need to be. I again will tend to start a little slower for vocals, middle of the road for guitars, and faster for drums.

You’ll want to again experiment with where to set this by listening to the sound. If the source sounds like it is pumping a little bit, slow the release down to help even it out a bit. If it feels like you might be losing something on the next note/beat, you likely need to speed the release up a bit.

Output. Most compressors have an output to help boost the volume of the end result, and here’s where I tend to see a lot of mistakes made.

Now that you’ve taken that 85 to 105 dB vocal and compressed it to a manageable 85 to 93 dB, you may need to increase the output a little to get it over those guitars and drums. Instead of reaching for the gain or trim knobs (which would then bring more signal into the compressor and would change how you’ve set your compressor), if you add 5 dB of gain to your output. you just took that 85-93 dB and made it 90-98 dB.

Especially Useful in Worship Environments
Compressors are a huge help to the sound man and used right they will help you get great sound out of your sources and give you the ability to get the mix where you want it. They’re especially useful in the worship environment where the voice of those leading the worship must always be present but not piercing, where more and more guitars are being used to lead the music but can’t overtake the vocals, and where many churches use acoustic drums.

Wrap Up
I truly believe that no one setting is right for any vocal or instrument. If you start with a lower basic setting and then adjust based off of what you are hearing, your compressors can give you a great edge to get your mix balanced and layered according to plan.

Just remember, you don’t want to compress something more than you need to. If you’re having trouble keeping a source in it’s place in the mix the compressor is the tool to help you make that happen.

Duke DeJong has more than 15 years of experience as a technical artist, trainer and collaborator for ministries. CCI Solutions is a leading source for AV and lighting equipment, also providing system design and contracting as well as acoustic consulting. Find out more here. Also read more from Duke at dukedejong.com.