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Compression And Gating:
In the years past, the control of the volume envelope of a sound (dynamics) would not have
been included as a necessary element of a great mix. In fact, dynamics control is still not a major part
of Classical and Jazz mixing. But in todays modern music, the manipulation of dynamics plays
a major role in the sound. in fact just about nothing else can affect your mix as a much
and in so many ways as compression.
I think that the sound of modern records (from mid 1980s to now) is compression. Audio
purist talk about how crunchy compression and EQ is, but if you listen
to one of those Jzzz or Blues records that are done by audiophile labels, theres no way they could
even complete on modern radio even though they sound amazing.
Dynamics Controllers:
Dynamics are controlled by the use of compression, limiting and gating.
For those of you new to mixing or need a review of clarification, heres a brief description of each.
See the glossary or any number of recording texts for complete information.
Compression:
Compression is an automated level control, using the input signal itself to determine the output level
This is set by using the threshold and ratio controls. compressors work on the principle of gain ratio
which is measured on the basis of input level to output level. For example, this means that every
4db that goes into the compressor, 1db will come out for a ratio of for to one (normally written as 4:1)
if the gain ratio of 8:1 was set, then for every 8dB that goes into the unit, only 1 db will come out.
Although this could apply to the entire signal regardless of level, compressor is usually not set up
that way.
A threshold control determines at what signal level of the compressor will begin to operate.
Therefore threshold and ratio are interlarded and one will affect the way the other works.
Some compressors (Like Teletronix LA2-A and UREI LA3 have) have a fixed ratio, but on most of
units the control is variable.
Most compressors also have attack and release parameters.
These controls determine how fast or slow the compressor reacts
to the beginning (attack) and end (release) of the signal. Many compressors have an
Auto mode that sets the attack and release in relation to the dynamics of the signal.
Although Auto generally works relatively well, it still doesn't allow for the precise
settings required by certain source material. Some compressors (like the dbx 160 series)
have a fixed attack and release which gives it a particular sound.
When a compressor operates it actually decreases the gain of the signal
so there is another control called make-up gain or output, which allows the signal to be boosted
back up to its original level or beyond.
Diagram A shows an input signal before compression.
Diagram B shows what the compressor does - turning down the volume once your signal crosses the threshold.
Diagram C shows the net output level (With the original signal shown as a dotted line).
The same box can do compression and limiting for the most part.
The difference is how they're set up. Any time for compression ratio is set to 10:1 or more the result is considered limiting. A limiter is essentially a brick wall for level, allowing the signal
to get only to a certain point and little more. Think of it as the same thing as a governor thats sometimes used on trucks to make sure that they dont go over the speed limit.
Once you hit 55 mph s (or whatever the speed limit is in your state), no matter how much you depress
the gas pedal, you dont go any faster. Same with a limiter, Once you hit the predetermined level, no matter
how much you try to go beyond it the level pretty much stays the same.
Limiting is usually used in sound reinforcement for speakers protection (there are some limiters on powered studio monitors as well), and not used much in mixing with the following exception:
Many engineer who feel that the bass guitar is the anchor for the song want the bass to have as little dynamic range as possible. In this case limiting the bass by 3-6dB (depending on the song) with a ratio of 10:1, 20:1 or even higher will achieve that.
Gating:
Although not used nearly as much now that console automation is so prevalent, gates are still a major
player in the mixers arsenal. A gate keeps a signal turned off until it reaches a threshold level, then the gate opens and lets the sound through. The gate can be set to turn the sound completely off when it drops below threshold or lower the level is predetermined amount. Depending on the situation, just turning the level down, a bit sounds more natural then turning it completely off, although completely off can be used as a great effect.
A gate (sometimes called noise gate or expander) is usually used to cover up some problems on a track
such as noises, buzzes, coughs or other low-level noises off mic. On louder guitar tracks
for instance, a gate can be used to effectively get ride of amplifier noise when the guitar player is not playing. On drums, gates can be used to turn off the leakage from the tom mics, which tend to muddy up the other drum tracks. A gate can also be used to tighten up the sound of a floppy kick drum by decreasing the after-ring.
Why add Compression:
If there is one major difference between the sound of a demo or semi-pro recording and a finished professional mix, its the use of compression. As a matter of fact, the difference between one engineers sound and another is, more often then not, his use of compression.
The big difference between engineers today is the use of the compressor. At one time or another i tired to compress everything because i was building a compressor and I wanted to see how it did on every instrument. Im a little ff on compression now because are so many that over use it. Everything is squeezed to death.
There are two reasons to add compression, to a track or mix: to control the dynamics or as an effect.
Controlling Dynamics:
Controlling dynamics means keeping the level of the sound even. In other words, lifting the level of the soft
passages and lowering the level of the loud ones so that there are not so much of a difference between them. Here are a couple of instances where this would be useful:
- On a bass guitar - Most basses inherently have a certain notes that are louder then others and some that are softer then others. Compression evens out these differences.
-On a lead vocal - Most signers cant sign every word of line at the same level so some words may get buried as the result. Compression allows every word to be heard.
- On a kick or snare drum - Sometimes the drummer wont hit every beat with the same intensity. Compression can make all drums hits sound relatively the same.
When controlling dynamics usually a very small amount of compression (2dB to 4dB or so at a 2:1 to a 4:1 ratio) is used to limit the peaks of the signal.
I like to compress everything just to keep it smooth and controlled, not to get rid of the dynamics but enhance them. Usually I use around a 4:1 ratio on pretty much everything I do. Sometimes on guitars I go to 8:1. On the bass, I hit that a little harder, just to push it up front a little more. Everything else is for control more then sticking it right up in your face.
I very rarely use a compressor to even out dynamics. Dynamics are something that I just cant get enough of. The compressors I like the most tend to be the one that actually help me get dynamics. That might be contradictory statement but if you are careful with the attack and release times you can actually get compressor to help you with it.
In the years past, the control of the volume envelope of a sound (dynamics) would not have
been included as a necessary element of a great mix. In fact, dynamics control is still not a major part
of Classical and Jazz mixing. But in todays modern music, the manipulation of dynamics plays
a major role in the sound. in fact just about nothing else can affect your mix as a much
and in so many ways as compression.
I think that the sound of modern records (from mid 1980s to now) is compression. Audio
purist talk about how crunchy compression and EQ is, but if you listen
to one of those Jzzz or Blues records that are done by audiophile labels, theres no way they could
even complete on modern radio even though they sound amazing.
Dynamics Controllers:
Dynamics are controlled by the use of compression, limiting and gating.
For those of you new to mixing or need a review of clarification, heres a brief description of each.
See the glossary or any number of recording texts for complete information.
Compression:
Compression is an automated level control, using the input signal itself to determine the output level
This is set by using the threshold and ratio controls. compressors work on the principle of gain ratio
which is measured on the basis of input level to output level. For example, this means that every
4db that goes into the compressor, 1db will come out for a ratio of for to one (normally written as 4:1)
if the gain ratio of 8:1 was set, then for every 8dB that goes into the unit, only 1 db will come out.
Although this could apply to the entire signal regardless of level, compressor is usually not set up
that way.
A threshold control determines at what signal level of the compressor will begin to operate.
Therefore threshold and ratio are interlarded and one will affect the way the other works.
Some compressors (Like Teletronix LA2-A and UREI LA3 have) have a fixed ratio, but on most of
units the control is variable.
Most compressors also have attack and release parameters.
These controls determine how fast or slow the compressor reacts
to the beginning (attack) and end (release) of the signal. Many compressors have an
Auto mode that sets the attack and release in relation to the dynamics of the signal.
Although Auto generally works relatively well, it still doesn't allow for the precise
settings required by certain source material. Some compressors (like the dbx 160 series)
have a fixed attack and release which gives it a particular sound.
When a compressor operates it actually decreases the gain of the signal
so there is another control called make-up gain or output, which allows the signal to be boosted
back up to its original level or beyond.
Diagram A shows an input signal before compression.
Diagram B shows what the compressor does - turning down the volume once your signal crosses the threshold.
Diagram C shows the net output level (With the original signal shown as a dotted line).
The same box can do compression and limiting for the most part.
The difference is how they're set up. Any time for compression ratio is set to 10:1 or more the result is considered limiting. A limiter is essentially a brick wall for level, allowing the signal
to get only to a certain point and little more. Think of it as the same thing as a governor thats sometimes used on trucks to make sure that they dont go over the speed limit.
Once you hit 55 mph s (or whatever the speed limit is in your state), no matter how much you depress
the gas pedal, you dont go any faster. Same with a limiter, Once you hit the predetermined level, no matter
how much you try to go beyond it the level pretty much stays the same.
Limiting is usually used in sound reinforcement for speakers protection (there are some limiters on powered studio monitors as well), and not used much in mixing with the following exception:
Many engineer who feel that the bass guitar is the anchor for the song want the bass to have as little dynamic range as possible. In this case limiting the bass by 3-6dB (depending on the song) with a ratio of 10:1, 20:1 or even higher will achieve that.
Gating:
Although not used nearly as much now that console automation is so prevalent, gates are still a major
player in the mixers arsenal. A gate keeps a signal turned off until it reaches a threshold level, then the gate opens and lets the sound through. The gate can be set to turn the sound completely off when it drops below threshold or lower the level is predetermined amount. Depending on the situation, just turning the level down, a bit sounds more natural then turning it completely off, although completely off can be used as a great effect.
A gate (sometimes called noise gate or expander) is usually used to cover up some problems on a track
such as noises, buzzes, coughs or other low-level noises off mic. On louder guitar tracks
for instance, a gate can be used to effectively get ride of amplifier noise when the guitar player is not playing. On drums, gates can be used to turn off the leakage from the tom mics, which tend to muddy up the other drum tracks. A gate can also be used to tighten up the sound of a floppy kick drum by decreasing the after-ring.
Why add Compression:
If there is one major difference between the sound of a demo or semi-pro recording and a finished professional mix, its the use of compression. As a matter of fact, the difference between one engineers sound and another is, more often then not, his use of compression.
The big difference between engineers today is the use of the compressor. At one time or another i tired to compress everything because i was building a compressor and I wanted to see how it did on every instrument. Im a little ff on compression now because are so many that over use it. Everything is squeezed to death.
There are two reasons to add compression, to a track or mix: to control the dynamics or as an effect.
Controlling Dynamics:
Controlling dynamics means keeping the level of the sound even. In other words, lifting the level of the soft
passages and lowering the level of the loud ones so that there are not so much of a difference between them. Here are a couple of instances where this would be useful:
- On a bass guitar - Most basses inherently have a certain notes that are louder then others and some that are softer then others. Compression evens out these differences.
-On a lead vocal - Most signers cant sign every word of line at the same level so some words may get buried as the result. Compression allows every word to be heard.
- On a kick or snare drum - Sometimes the drummer wont hit every beat with the same intensity. Compression can make all drums hits sound relatively the same.
When controlling dynamics usually a very small amount of compression (2dB to 4dB or so at a 2:1 to a 4:1 ratio) is used to limit the peaks of the signal.
I like to compress everything just to keep it smooth and controlled, not to get rid of the dynamics but enhance them. Usually I use around a 4:1 ratio on pretty much everything I do. Sometimes on guitars I go to 8:1. On the bass, I hit that a little harder, just to push it up front a little more. Everything else is for control more then sticking it right up in your face.
I very rarely use a compressor to even out dynamics. Dynamics are something that I just cant get enough of. The compressors I like the most tend to be the one that actually help me get dynamics. That might be contradictory statement but if you are careful with the attack and release times you can actually get compressor to help you with it.
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