Threshold: The threshold will depend on the vocalist
and the room you’re working in. There’s no set
threshold. It’s something you’ll have to tinker with to
get the best setting for your environment.
Ratio: Generally speaking (and you’ll read this almost
everywhere), vocals should be compressed at a ratio of
Attack: You want to set a fast attack time. Attack is
the speed at which the compressor kicks in and does its
work. Too slow of an attack time will cause the vocal
to be mushy and lack punch.
Release: This is how long until the compressor stops
doing its work. I would set a medium-slow release time
as a starting point. You’ll have to adjust it for your
own voice and get the best setting. Use your ears as a
Output: The output is the signal level that the
compressor returns. If you need to add a little gain to
your signal post compression, turn up the output a bit.
Be careful that you do not distort your compressed
signal by turning up the output too high.
Look to start vocal compression with a compression
ratio of 2:1, using a soft knee, and fast attack time.
There is a fine balance between having a too fast
release time and having a too slow release time. If
your plugin has auto-release time settings, you may
want to use these. You may need to set a deeper
compression ratio, depending on the voice and
recording. Never go more than 8:1 with a voice-over,
and even that is a fairly extreme setting.
Be cautious of compressors set too high, or using auto-
gain makeup. This can easily induce noise to the audio,
or rather enhance existing noise in the recording. Of
course, you can use a noise gate to "hide" the noise,
but noise gates can also create more problems if the
threshold is set too low or too high.
Setting Gates: Compressors do increase the
presence of noise in a signal, and they do affect
dynamic range. Noise can be taken care of by gating
the signal. When it dips below a certain threshold,
the audio signal is muted. This is effective for
getting rid of low level noise you do not want in the
file, such as bleed from headphones, or the vocalist
moving, turning pages on lyric sheets, etc. Gates have
two parameters: 1) The noise floor threshold, and the
Rate. The Noise floor threshold eliminates all of the
signal when it dips below the threshold, which is set
from -50db to -10db. I keep mine set to -30db. Yet one
has to be careful. If the gate is set too high, then
the attack of the vocalists words may be cut off or
come in too abruptly. The Rate parameter "fades out"
the audio signal as the gate come on. This is
effective to prevent the gate from chopping off the
tails of the words. Usually a rate of 1-1.5 sec is
Setting Threshold: The Threshold is the all
important level at which the compressor kicks in. If
you set the threshold to -10, it will leave all of the
signal under -10 alone. When the signal exceeds -10
then it starts compressing at the ratio. -10 is an
excellent place to start. Don't confuse this with the
fact that your gear is outputting -10 or +4 impedance
wise. Though the threshold seems like it is a volume
control, it is not. It is merely telling the compressor
at what level compression takes over the signal.
Setting the Ratio 2:1 is probably the most common
setting for a compressor recording or playing back
nearly anything. A great starting point. What this
means, simply, is that it takes 2 decibels of sound
energy to raise the output meter by 1db. You can read
the 1st number as the db IN and the second as the db
OUT. Again, 2db IN equals 1 db OUT. With 2:1 you
simply divide by two.
Shure SM58 Dynamic Handheld Microphone
Answer this: If your vocalist was singing at -10db
and suddenly got 20 db louder, without compression,
where would the meters post?
-10+20=+10. The meters would post at +10
Correct! This is way too loud and would ruin the
track. Now, if you had 2:1 compression applied, where
the output is half of the input, where would the output
-10+(20/2)= zero db!
Yes - Why? The vocalists 20db burst was compressed
to an actual 10 db difference in gain. (the ratio 2:1
is the same as 20:10, or half). (Note, you don't have
to record all the way up to 0db, leave a cushion for
the best sonics)
Lets go one step further, If you had the compressor
set at a 10:1 ratio what would that mean? It would
mean for every 10 decibels of gain the meters would
only go up one db. So in our example, then, the 20 db
burst would only let the meters go up by 2db (10:1 is
the same as 20:2, or 1/10th of the original sound),
Since they started at -10, the overall level would be
only at -8 during the sudden 20db boost. Hardly any
change in the output level at all. Would that sound
"squashed"? You bet.
Setting Attack and Release: These settings can be
tricky as they can "delay" the effect of compression on
the attack and make is hold on a bit too long on
release if set improperly. I suggest till you get
these tricky settings figured out (which takes quite a
bit of experimentation) you simple use the fastest
attack and enough of a release so the vocal is not
boosted as the word trails off. Otherwise a word may
pump on you un-naturally.
Setting the output: This is the final adjustment
as the signal leaves the compressor. It's sometimes
called the "make-up gain". They call it that because
compression often lowers the overall signal and you may
need to boost it back up. Basically you want to
optimize this so it does not ever go over 0db in the
recorder. With luck you should see a consistent
healthy level on the recorder's input meters regardless
of how loud the vocalist is singing.