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 we’re feeding have distortion as well, the
distortion is additive (actually, mathematically,
it’s worse; with noise, for example, you add
the squares). Many types of distortion are
non-linear—they sound dissonant. If you distort
the distortion coming from the mic (with
electronics), you have audibly destructive fresh
distortion components. If you think your chain
is clean with a conventional microphone (and it
might be!), with a good ribbon and transformer/
preamp, it won’t be just clean, it’ll be pristine.
The ribbon microphone is the cleanest mic
out there. The primary reason is the low mass
of the diaphragm. Less inertia means an intrinsic
ability to follow waveforms more accurately.
Figure-8 pattern typical of ribbon microphones |
Cardioid (heart-like) microphone pattern |
Ribbon mics ruled broadcast for years, and
recording studios always have ribbons available.
Besides their natural spectral balance
and superb transparency, they also have
great pattern flexibility. Typically, ribbon
mics have a bi-directional sensitivity pattern.
As you can see from the diagram,
when viewed from above, you have essentially
identical pickup of sound front and
rear with good side rejection. If you use a
pair of these correctly, you end up with the
natural, open sound of the famous Blumlein
Pair microphone array. In addition, many of
today’s ribbons give you the option of cardioid,
hypercardioid or even omni-directional
patterns. Some even allow you to set almost
any pattern you can dream up.
Some ribbon mics have long ribbons with
a short acoustic path around the magnets,
while others are the opposite. Pros select
mics with these parameters in mind, but for
many others purchase decisions are often
dictated by pricing rather than coverage
and pattern. In theory, a longer ribbon has
more limited vertical pickup pattern—better
for cleaner sound, as the reflective ceiling
and floor surfaces contribute less coloration
and reverb. There are applications, however,
when you want the added ambiance.
Today’s ribbons can actually be used on
stage. Combining a variable pattern with
natural spectral balance and head-turning
transient response can give you the very
best of a good acoustic guitar—about
a bazillion times better than a “quacky”
onboard pickup. From oboes to piccolos,
from violins to French horns, ribbons work
great with acoustic instruments. No matter
the music, ribbons rock.
Due to the large size of the “motor,” ribbon
mics have been large from day one. Not all
are large. Some look like regular hand-held,
dynamic moving-coil mics, while some look
like Johnny Carson’s. The old RCAs are dripping
with vibe cosmetically and many companies
emulate that look.