This waveform of a plucked note shows a strong attack, followed by a rapid decay.
BY E. E. BRADMAN
Have you heard the one about the party at Effects Central?
Tough guy Octaver shows up, a sweet
little Chorus on his arm, and that funky
character Envelope Filter—accompanied
by Synth Bass and a strange dude everyone
calls Pitch Shifter—saunters in, dressed
to shock. Overdrive and his brother Fuzz
buzz by, as Wah and Autowah squeak back
on the sofa with Phaser and Flanger. Suddenly,
Compression enters the room, and
the guest of honor, Clean Boost, gives him
a strange look. The party screeches to a halt
as Looper, that night’s DJ, stops mid-song.
“What are you doing here?” says Envelope
Filter, looking ready to throttle Compression.
“You’re making all of us feel small!”
Corny jokes aside, compression really
does get a bad rep. It doesn’t have the cool
factor of its brawny, ballsy, or downright
freaky effects kin, and its reputation as a
tone killer is unparalleled. Besides, isn’t compression
for suckers who can’t play evenly
and speakers that aren’t tough enough to
handle active basses?
Truth be told, compression is one of the
most important tools for recording bass,
and it can be quite useful in live situations,
too. When used properly, it can help define
a bass’s place in a live or studio mix while
taming the instrument’s wide dynamic
range. Because bass forms the foundation
of a track, it’s important that the bass level
doesn’t jump around in the mix, which can
be tricky since bass players—especially those
of us with mediocre technique—don’t always
exercise precise control over our dynamics.
Regardless of technique, though, every bass
player who has ever played even a mid-size
gig or recorded a bass line has been compressed.
The secret is that a good engineer
or sound person knows how to use just
enough compression that you—and the listeners—
can barely tell it’s there.
Simply put, compressors squeeze the dynamics
of a sound so that the loud sounds are
softer and the soft sounds are louder. A compressor
uses a high-gain preamp and a control
circuit that alters the preamp gain based
on the compressor input. As you send more
signal into the compressor’s input, the control
circuit senses this and turns down the
preamp gain to maintain a more consistent
output level. The louder you play, the
more your bass signal will get slapped down,
while the soft parts will get turned up a bit.
Limiters do the same thing, but they only
restrict peaks, without touching the lowvolume
parts; they can do a rather hamfisted job of processing dynamics. Luckily,
most modern compressors are limiters, too.
Compression mellows the attack and amplifies the decay.
The best way to understand what a compressor
does is to plug your bass into one,
tweak the knobs one by one, and listen. It’s
a good idea to bypass the compressor every
so often to remind yourself what your natural
bass tone sounds like, and A/B it with the
compressed tone. Start by setting the compressor’s
INPUT level. One thing you’ll notice
is that compression lowers the overall average
levels of your signal, but don’t be tempted
to slam the compressor with more juice: The
all-important OUTPUT GAIN knob will help you
make sure you get the volume you need.
Next, set the THRESHOLD level, which determines
how loud things can get
before the compressor kicks in.
A low threshold means you want
the compressor to be very sensitive,
whereas a higher threshold
means you’ll have to really
whack the string to get the compressor to
tamp down. Next, use the RATIO (or SLOPE)
control to tell your compressor how much
compressing it needs to do. If you set the
THRESHOLD to –10dB and the RATIO to 3:1,
for example, for every 3dB of signal above
–10dB that goes into the compressor, only
1dB comes out. Adjust your output gain
accordingly. Now that you’ve decided when
and how much your compressor needs to
jump into action, use ATTACK to tell it how
quickly it should react to your signal. The
RELEASE knob (sometimes labeled DECAY)
allows you to control how long it takes
your compressor to stop compressing after
it’s been triggered.
Every compressor is a little different, and
it’s worth experimenting with different types
to see what works for you. Some compressors,
for example, have a HARD KNEE/SOFT
KNEE switch, which controls how sharply
the compressor does its job. If you choose
soft knee compression, the compression
ratio gradually increases as the input level
approaches the threshold. With hard knee
compression, the signal undergoes the specified amount of compression the moment
it crosses the threshold. Hard-knee action
creates more punch; soft knee may work
well if the level variations are extreme, as
it allows for more dynamics.
With a compression ratio of 4:1, exceeding the threshold by 16dB at the input (here, going from –8dB to +8dB) yields an output increase of 4dB.
Other compressors or pedals have only
two knobs: COMPRESS (or SUSTAIN) and
LEVEL. If this is the case, consult the specs
to see whether the COMPRESS knob is for
setting threshold, ratio, or attack parameters,
and use the LEVEL knob to control
your output gain. If you’re using a studiograde
compressor, you might have a GATE
control, which turns off the audio when it
goes below a defi ned threshold. It’s great
for removing noise.
Most bass players choose between rackmount
and pedal compressors. Rackmount
units are usually either tube and solid-state;
many people favor tube compressors, such
as the Teletronix LA-2A and the Tube-Tech
CL1B, because you can generally get more
out of them before you start to sense the
signal being squeezed. Some of the bestknown
solid-state compressors include the
dbx 160 and the UREI 1176. Models such
as the Avalon VT-747SP can be switched
between tube and solid-state. While there
are dozens of stompbox compressors on the
market, Aguilar, DigiTech, EBS, Electro-
Harmonix, MXR, and Markbass are just a
few manufacturers that have compressors
aimed specifically at bassists.
If you’re a slapper or rocker who digs in—
and especially if you play with a pick—compression
can help tame those sharp peaks
and rein in the dynamic variance between
plucks and thumps. You love that tight Jaco
Pastorius tone? Lots of people use compression
to help them sound more punchy. If you
go for a warmer, old school R&B or reggae
tone, you’ll appreciate compression’s ability
to tighten up the bottom end and make your
bass sit better in a mix. If you prefer long
notes and you’re going for that big, country
bass sound, use compression to help get sustain:
With the peak volume at the beginning
of the note—the attack—snipped down, the
listener doesn’t hear the natural decay of a
plucked note, which can sound very legato.
Whatever style you play and whether
you’re in the studio or onstage, compression
can help you get the tone you want.
Who knows—one day, compression could
be your main squeeze.