| Remember that "the compressor [is] acting like your own dedicated
engineer for that one track. It will monitor all the incoming signals and then act like it
is pulling down the fader the instant that high volume peak occurs." In other
words it reduces gain on the high-level peaks. "How much" compression you
are using is determined by how much the gain is reduced on the peaks. After you have
set the ratio, attack time and release time, the threshold setting determines
"how much" compression you are using. |
| There is usually a series of lights (or possibly a meter) that tells you
how much the gain is being reduced. Having this meter read "-6dB" on the
louder peaks means the peaks are being brought down by this amount. This amount of
compression (6dB) is usually a good guideline. In more severe cases, or if you are
trying to get an extra-even track level, you could adjust your threshold to read
"-10dB" on the peaks. Beyond this point the instrument begins to sound
lifeless and you can really hear the compressor work. This is fine if you want that
effect, but generally I avoid this much compression. |
| Stereo Compression |
| Probably well over 90% of the CDs released have the entire stereo mix
compressed. A stereo compressor is two compressors working together, one for the
left signal and one for the right signal. But you really can't just hook your stereo
mix signal though two different compressors, because they have to "work
together." The stereo compressor always reduces gain on both the left
& right signals by the same amount, even when only one side has the uncontrolled peak.
If the two (left & right) compressors operated independently, it would sound
like someone was playing with the balance control. A stereo compressor will usually have a
"stereo" mode or a "link" button that will need to be activated.
"Link" simply means that both channels will be linked to work together,
rather than separately. If you are using the stereo compressor as two independent
compressors (like for two individual instruments), take the unit out of the stereo mode or
turn off the link. |
| The settings most often used for stereo compression of the entire mix
include a low ratio (2:1 or 2.5:1), fast attack, medium release and the threshold
control adjusted for about 6dB of gain reduction on the loudest peaks. Overall compression
of the stereo mix is usually sounds best with a soft knee (if available). |
| Compression of the mix makes the average level louder. You
apply gain reduction and then re-adjust your output level control for a good level,
causing everything to sound louder to the ear. Also the ear itself compresses really
loud sounds, so adding compression "sounds louder." |
| The Down Side |
| Compression sounds wonderful - right? Well, there can be
side-effects you should watch out for. A lot of these side-effects have to do with
background noise. When you adjust the threshold to cause compression and then boost
the output level to restore normal signal strength, you effectively boost the strength of
low-level sounds. Some of these sounds we don't want - such as shuffling of
the feet, air-conditioning noise or electronic hiss. If you are recording more than
one instrument at a time, the leakage
of the wrong instrument sound into the microphone is also an undesirable sound. If
you add a lot of compression for the super-even effect it causes, these background noises
can get really loud. Sometimes you can hear the background noise "pump,"
meaning you hear background noise slowly rise between the vocal lines (for example).
|
| These background noises getting loud is usually just a
sign that you are using too much compression and the solution is to use less.
Sometimes a bit of pumping can be corrected by adjusting the release time (usually making
it faster). Another solution is to use a noise gate after the compressor which
turns off the signal when the instrument isn't playing. Some (more expensive)
compressors have noise gates built in for this reason. |
| De-esser |
| When a singer sings a word with an "S" there is a blast of air
that rushes through the teeth, causing a high-frequency peak. These "S"
blasts can easily distort analog tape and also becomes annoying in digital
recording. Many compressors have a "Deessing" setting that can be used to
correct this. When a compressor is in the deessing mode, it becomes more sensitive
to the higher frequencies; in other words it will reduce gain more for loud
high-frequency peaks than it will for other peaks. |
| You say you don't have a dessing feature on your compressor? -
Never fear - how to "make one" out of a stereo compressor is listed in the
"Advanced Techniques & Tricks" given below. |
| Advanced Information, Techniques & "Tricks"
with Compressors |
| So you feel good about the basic operation of a compressor? You
want more? Click on the links below! |
|
PLEASE NOTE THAT MANY OF THE ADVANCED ARTICLES WILL ONLY BE AVAILABLE
TO PAID SUBSCRIBERS OF THE NEW "ALEXANDER" MAGAZINE AFTER FEBRUARY 1, 2000 |