For many bassists, a compressor is a most
mysterious piece of gear. Though most
can suss out that they do just what their
name implies—i.e., compress the dynamic
range of your signal—the task of adjusting
a compressor correctly can be daunting for
the uninitiated. Happily, the MXR M87
Bass Compressor gets the job done pretty
easily, while still allowing for a good range
of variation from basic settings.
Tweaking the Knobs
Though pedal compressors often have too
few controls to provide the top-quality compression
one gets from a pro rack unit—that
invaluable-but-hard-to-detect quality that you
don’t really notice until you A/B it with the
uneffected signal or watch a channel meter—
happily the MXR Bass Compressor has its
own version of a rack compressor’s five most
potent controls—threshold, attack, release,
ratio, and gain—plus a gain-reduction meter.
Although dealing with five knobs and a meter
may sound daunting, the basic functions of
this pedal are fairly easy to use. As the concise
owner’s manual suggests, adjusting the Input,
Output, Attack, and Release controls to noon,
with Ratio at 4:1, is a good starting point.
To test the M87, I plugged in a P bass
loaded with a Seymour Duncan Quarter
Pound pickup and strung up with fresh
roundwound strings. With the basic settings,
the MXR easily provided a natural
fingerstyle sound that revealed some compression
on the meter, yet went nearly
undetected to the ear until I used the
true-bypass footswitch to A/B the sounds.
Turning up Input and tweaking Output
increased the amount of compression while
keeping the volume the same.
Essentially, the Input control on the MXR
Bass Compressor functions like a Threshold
control on a rack unit. The Output control
provides the “makeup gain” to bring back
what was lost after the compressor lowered the
volume. Through all this tweaking, I found
the gain-reduction meter to be a handy feature
that enabled my eyes to guide what my ears
were hearing. The manual suggests adjusting
Input until three to seven bars show on the
meter. Three bars on the peaks provides just
a little compression, while seven bars knocks
down the peaks considerably—especially on
the lower notes that pack more energy.
Know Your Limits
Most adjustable compressors can also serve
as a limiter by changing the ratio to 20:1 or
higher and dialing-in fast attack and release.
This is a useful setting for slappers who
want to even out the sound without backing
off on their attack. I tried this on the
M87, turning both the Attack and Release
controls fully clockwise for the shortest
times and setting the ratio to 20:1. I then
adjusted Input until I saw the gain-reduction
meter quickly peak toward the left and
return to the right. The actual attack and
release times are not labeled on these controls,
but it’s easy to remember that clockwise
rotation creates faster times. From
there, rely on your ears and the meter.
Either as a compressor or a limiter, the
M87 did its job remarkably well. It added
no noticeable noise to the signal and left
my bass lines intact—as long as I didn’t get
too wacky with the settings. Its compact
size makes it a handy tool for real-estate-conscious
bassists, and the small, sturdy
knobs feel ready for many a gig.
Unlike some compressor pedals I’ve tried,
the M87 was good at doing its job without
having a negative impact on tone. Some
two-knob compressors can become obtrusive
if you’re not judicious with the settings,
overly squishing the sound while adding
a bit of noise along the way. It takes just a
little bit more effort to set up the M87, but
the bright, three-color gain-reduction meter
serves as a helpful guide.
I would have liked easier access to the
battery compartment, because changing the
9-volt battery requires removal of four stainless-steel screws. I had a little trouble reinstalling
one of the screws, especially after it tried
to cross-thread into the softer aluminum box.
This is of little concern if you’re using wall-wart
power, but I wouldn’t want to change
its battery on a dimly lit stage. Some bassists
might also prefer a compressor with variable
or higher ratio options for limiting, though
a 20:1 ratio is more than enough for most
limiting purposes. Overall, if you’re trying to
avoid hauling a rack around and have room
on your pedalboard, the M87 can become a
handy, valued addition to your rig.
you’re looking for a transparent,
flexible compressor and can deal
with multiple knobs.
you require fully variable ratios or a
one-knob, set-and-forget compressor.