you can actually improve the performance of
a mediocre ribbon mic by replacing the diaphragm if you do it correctly.
The electrical signal generated by a ribbon
is different from that of a dynamic mic, but
technically speaking, a ribbon mic is a type of
dynamic microphone—they both move back
and forth in a magnetic field. Older ribbons
differ from modern designs in significant ways.
Older designs have very low output and very
low impedance (0.2 Ohm in many cases). This
impedance is so low that we need to bring it
up to drive what we usually consider to be low
impedance lines, so a transformer is used to
increase both the signal and the impedance.
Transformers are tricky. In a guitar amp, one
can hear the difference between an ordinary
transformer and a boutique equivalent. The
same applies to microphone transformers. If
you lack the inclination to replace the ribbon
element, a transformer upgrade can yield
equally impressive results, but if distortion
of a signal is to be kept as low as possible,
a good transformer can be quite expensive.
Fortunately, many of today’s designs have
plenty of output—even more than moving-coil dynamic mics in some examples. In either
case, a high-quality, low-noise microphone
preamp can sound great. With the right
preamp, you might be able to forgo the supplied transformer. Note that you might need
60dB of gain, so audition any preamp you buy
not only for sound quality, but also for noise.
Condenser mics need a power supply.
Ribbons do not. Older ribbon mics could be
damaged by hooking one up through a preamp designed for condensers, so be careful.
Many preamps allow a choice. Most ribbon
mics have on-board transformers or preamps.
The latter may need a phantom 48V power
supply from your mixer, just like a condenser.
Use care here: many ribbons will be damaged
if hooked to a phantom power supply. Never
hook up a ribbon mic to your mixer without
checking. Newer designs are more likely to
shrug off the mistake, but read the manual.
Speaking of shrugging off mistakes, another
difference is durability. Some of the older—but
really great-sounding—ribbon mics would fail
from physical shock, but often stood up well to
high SPLs. This can be tricky, too. A full symphony orchestra can play louder than my blues
band usually does. A ribbon can certainly be
used in high SPL environments, but be careful
about a loud singer blasting away right into the
mic without a pop shield. In fact, it’s good idea
to always leave the pop shield on, especially
when transporting or setting up the mics. Once
set up, you might be able remove it, depending on the design, unless you’re recording a
singer. Today’s ribbons are far more rugged.
Even so, never scream or blow directly into
any ribbon without a pro-quality shield. In fact,
don’t blow into a ribbon mic, period.
What Are They For?
In a word: fidelity—accuracy in details, transient
response, incredibly sweet and clear highs,
clean mids and rich, accurate lows… probably
the most natural presentation ever. Yet, they
can be lush and romantic, with great warmth,
and without bloat. Mic techniques coupled with
the right electronics give you flexibility. Want a
bit of bloat or extra warmth? Like their dynamic
moving-coil brethren, ribbon mics suffer from
proximity effect. Get really close, get lots of
bottom. Place the mic a couple of feet away,
clarity and balance start to return. Some models have a choke or high-pass circuit on board
to attenuate low frequencies for close micing.
Can’t we get this level of performance with
any decent mic? Nope! Here’s why: If you start
with a non-linear transducer, be it loudspeaker,
phono cartridge or microphone, it’s very difficult to linearize. If you start with a distorted
transducer, it’s even worse. There are distortions present in all transducers—even if you
think you can’t hear them. Since the electronics