What Is A Compressor?

A compressor is a device that reduces (compresses) the dynamic range in a sound sources softest point to its loudest point to smooth the output, and can bring your audio material up to spec with professional recordings. An instrument that goes from very quiet and very loud over the course of a song can be difficult to record and mix. Either the quiet parts get lost or the loud sections overload the recording.
 

You can use a compressor to turn down the loud bits automatically, making the instrument easier to record or mix. You can also use compressors to make instruments sound fatter and bigger, and can be used to beef up vocals and to bulk out your finished mixes. Most audio professionals use compressors in every piece and sometimes on nearly every track in every piece.

Here are some features you may find on a compressor:

 

Threshold
This is where you set the limits of the compressor, meaning at what level of dB do you want the compressor to start compressing. Using a setting near to zero would incorporate the compressor ever so slightly, if you want to add more compression set the levels to a more negative number.

Attack
Attack basically refers to the speed at which you want the compressor to kick in. Do you want compressor instantly or would you prefer it to gradually phase in.

Release
Once the compressor has kicked in, how fast or slow do you want the compressor to release and no longer compress the signal?

Ratio
The ratio refers to how much the compressor is going to reduce the range of the signal.

Gate
A gate is a device that will eliminate any room noise, making recording deadly silent. It works by turning off the audio when it drops below a defined level. When the gate is open it simply lets any sound you plug into the input of the box straight through to the output. A closed gate doesn't let anything through - you just get silence on the output.

 

When the sound at the input is below a certain level, known as the 'threshold' the gate remains shut. When the input goes above the threshold, the gate opens and the sound is carried through to the output. Then when it drops back down again, the gate closes behind it. It can be used for example, to filter and eliminate any unwanted background noise. When you stop playing, and the sound drops below the threshold it will cut the sound to silence.

A separate outboard compressor is a great tool to have as you can tame and level the sound source before it enters the computer. However there are of course drawbacks to this, once the sound is in the computer you will not be able to “uncompress” the sounds. Use the compressor moderately as too much compressor can drag the life out of your songs. Overuse can result in all notes sounding the same and take away the dynamics of lighter and heavier notes.

 

 

 
The Samson SCOM is a dual-channel, signal rack space Expander/Gate, Compressor/Limiter, and Enhancer designed to reduce noise, increase loudness, prevent clipping, and recover high frequencies that might get lost during heavy compression.

The Expander/Gate section features a variable Threshold control, a Fast/Slow switch for setting release times, and Open/Closed LEDs for precise monitoring of the gate's operation.

  
The Compressor/Limiter controls include Threshold, Ratio, Attack, Release, Output, and a switchable "Auto" function (attack and release times can be set manually or automatically).

 

 
Some compressor/gates provide less than musical compression, coupled with gating that swallows transients-or closes early, cutting off decay and reverb tails. The superb engineering in the 266XL ensures that both its compression and gating provide versatility and excellent sonic performance in situations where other compressor/gates typically produce undesirable processing artifacts.

When using the 266XL's Auto Dynamic Attack and Release controls, artists and engineers will find that the center

  
settings deliver classic dbx compression, while the full control range produces voicing’s that extend from slow "leveling" to aggressive "peak" limiting.

The Auto Dynamic circuitry continuously adjusts the actual attack and release times to optimally match the program material. Since users aren't restricted to using the Attack and Release controls only in "peak" operation, they can tailor the response of the 266XL for individual tracks, mixed program material, special effects, or system protection.

 

 
The PRO VLA is a multi-purpose tool for audio engineering and recording. Enclosed in a 2U (3.5" high) rack-mountable chassis are 2 independent channels of analog leveling/compression designed to work seamlessly with any recording, sound-reinforcement, or electronic instrument setup.

ART's PRO VLA circuitry is a hybrid design utilizing the latest and most advanced analog and tube technology. Using a transformer less design throughout, the PRO VLA maintains exceptional signal integrity and extremely low

  
noise. In addition to making signal levels more manageable, it is common practice to apply compression or limiting to a signal to make it louder or more "in-your-face."

The PRO VLA allows you to add more compression without sounding like you're squashing the daylights out of the signal. Unlike typical compressors which use VCA's to control level detection, the PRO VLA is very musical. The nature of its operation is much like the way your eye adjusts to light. Just as your eye transparently adjusts to changes in light, the PRO VLA adjusts to changes in signal level.

 

 

If your budget doesn't quite allow you to spend this amount of money just yet, then an excellent alternative is to use compression software on your computer. Most modern sequencers have software compressors these days. These come in many different styles and types and many of them sound very good. This method involves you recording as usual using a microphone, mic preamp, and converter to get the sound into your computer then using a plug-in to add effects later.

The sound recorded onto your computer will be in it's most basic form, which then enables you to play around with compression rates and gives you the option to undo, and restart without having to re-record the entire piece of music.

The Renaissance package by Waves is an excellent piece of software that offers software compression and a whole heap of other effects. If you prefer to add effects after recording then this is a great solution. For more of software and sequencing packages click here.