When using a compressor with other effects, many players put it first
in the chain. First, it gives you a good signal to work with. When the
compressor is on and the output level is increased, the noise will be
amplified along with the instrument's sound. Other effects can introduce
more noise, so if the compressor is placed after those effects, it will
end up amplifying their noises, too. To reduce all this noise while not
playing you need to use a NOISE
You can increase the sustain of an instrument, lets say guitar,
because the compressor will try to maintain a constant output level for
a given input level. You can get the "STING" or
"POLICE" sound by using a compressor near it's limits. Because
compressors reduce dynamic range they make Accents much less
noticeable. So you should be careful not to kill the sound of the
For example: If you have a singer that can't seem to sing
directly into the microphone (they move around) a compressor will help.
So would nailing him to the wall, but a compressor is much more humane.
You can also use compressors as a LIMITER where if a signal gets to
loud the compressor/limiter will kick in and reduce the volume so it
doesn't distort. In a digital studio limiters are especially useful.
Recording Drums would be rather risky without a limiter on the
microphones (limiter = a compressor setup in limit mode). Drums have a
lot of spikes (transient sounds) that can go beyond the digital brick
wall. When this happens you pretty much lost the recording.
Ducking a Signal
Doing voice-overs for radio commercials you will probably run into
this. For instance if you want the background music to be reduced while
the announcer is speaking then ducking is a way to do this. You can also
apply ducking while recording a vocalist that is having trouble hearing
themselves. The music will be reduced while the singer is singing and
then get louder when he stops singing.
In essence ducking is the dynamic control of sound 'A' (Music) using
the signal from sound 'B' (the voice). Most compressors have this option
in the form of a 'Side Chain' input. Plug the output of voice into the
'Side Chain' input and connect the music to the input of the compressor.
Adjust as required (see below):
A 'De-Esser' is a frequency dependent compressor. You may be saying
"What?". A de-esser will reduce the volume of the 'Sss'
frequencies while letting the rest of the voice pass through un-changed.
This is very useful for voice overs and vocals where the Sssss' can be
How to Use a compressor:
You will need:
- A compressor.
- An audio source to be compressed (eg. mic, guitar, or output from
a sound card, etc).
Plug the audio source in to the compressors input jacks.
Adjust the levels so you're not overdriving the compressor.
Set the threshold level. This is the point at which the
compressor will kick in and take effect. Signals below this level will
not be affected. Signal levels above the threshold will be reduced
according to the compression ratio.
Set the compression ratio. Ratios of 5:1 or less will produce fairly
smooth compression; ratios of 10:1 or more will produce more severe
cutting off. For Voice a 2:1 or 3:1 should be ok.
Set the attack time. This is the delay between detection of a signal
above the threshold, and the commencement of compression (ie. the time
it takes to "attack" the signal).
Set the decay time. This is the time taken to release the signal from
Adjust any other settings on the compressor. If you don't know what
they are, try to put them on automatic, or disable them.
Set the compressor to a threshold of 0db, and a compression ratio of
3:1. In this case, all signals below 0db will be unaffected, and all
signals above 0db will be reduced by 3db to 1 (ie. for every 1db input
over 0db, 1/3db will be output).
Compression is one of the staples of virtually every recording studio,
from basement demo stations to world-class super-studios. But just what
do you do with it? Here are five ways of using compression to squeeze
the most out of your music:
1) Tame the wild vocalist. By adding a bit of compression on vocals,
you can both make up for a singer's tendency to move close to or away
from the mic, and to temper the occasional peaks that might otherwise
overload your recording medium. This is especially important for digital
recordings - digital clipping will irreparably ruin a take in an
2) Add sustain. Guitarists know this one well - by adding compression
with a long release time, you effectively lengthen the tail of the
signal. On attack, the peak is squashed, and as the signal decays, the
compressor opens up, allowing more of the signal through. Don't limit
yourself to guitars, though. Play around and see what works.
3) Add punch and clarity to the bass. By reigning in the bass signal,
a compressor helps give the sound definition and power. When you really
want your bass line to stand out, a healthy dose of compression may be
just the ticket!
4) Special effects. One of the hazards of compression is that the
lowering and raising of volumes can lend a breathing or pumping sound to
the compressed track. However, if you like to live on the cutting edge
of composition, this can be used to good effect (pardon the pun!). Get a
good rhythmic groove going that really works the compressor, and
experiment with the results.
5) Compress the entire mix. By adding high-ratio compression (or
limiting) as you mix down to stereo, you increase the apparent overall
level of your tune, and give it maximum punch. But beware - too much of
this can completely suck the dynamics out of your music, leaving it loud
So what do you need to get started? There are dozens of solutions,
but here are some of my favorites from across the price range:
For high-end quality, the Avalon VT-747SP is the way to go. At
$2,199.99, it's not inexpensive, but its outstanding tube/discrete
design, attention to detail, and painstaking construction all add up to
one amazing piece of gear.
Supporting the mid-range price zone, the Joemeek SC2.2 and dbx 1066
provide pro-studio grade compression using discrete technology to keep
the costs down. Both are recognized leaders in the world of studio
For the budget-minded, you can't go wrong with the PreSonus Blue Max.
At under $150, you get a half-rack space mono compressor that lets you
go fully automatic with built-in presets ideal for those new to
compression. For the already-initiated, full manual mode lets you work
compression magic to your heart's content!
Whatever level you choose, these sonic tools will always have a place
in your rack, as each compressor adds its own unique signature to the
sound. Try 'em and see!