FEATURE
Ribbon
Microphones
BY FRANK MALITZ
As this issue of PremierGuitarfocuses on recording, we’re going to examine a device
most of us rarely encounter (except on recordings and in movies), known as the ribbon
microphone. Rarely used at guitar gigs, the ribbon mic is derigueurin recording studios
all over the world. We’ll examine the reasons why in a moment, but first…
Some History
Microphones were common enough since
the advent of the telephone. These mics
were carbon-granule type: sound vibrations would cause the granules to vary their
conductivity, resulting in an electrical signal
form of the sound. They were quite rugged, and even the first men in space and
on the moon spoke though antiquated, but
dependable, carbon mics. Unfortunately,
they had poor frequency response, so they
were eventually constrained to telephone
use only until around 1970.
Dynamic microphones are the de facto
standard for most of us. They sound great,
are relatively simple and cheap to manufacture, are rugged, and have easily controlled
coverage patterns. A dynamic mic is like a
loudspeaker in reverse. The key element in
a dynamic mic is a diaphragm attached to a
little coil, which usually fits into a magnet.
When sound vibrates the diaphragm back
and forth, a tiny voltage is generated, which
is an analogue of the sound. Most dynamic
mics sound pretty good, with the best units
offering up excellent performance—
especially for the money spent.
It wasn’t long before carbon mics had competition. Crystal mics actually used crystal,
like a cigarette lighter. By using a mechanism to push on the crystal (or a ceramic
mounted equivalent), electricity is generated. While crystal and ceramic microphones
surpassed the old carbon types in performance, you and I would never use one on
stage or in the studio. Their performance is
still rather inadequate for quality recording
(blues harp players excepted).
How many of you know the name Walter
Schottky? Ol’ Walt is primarily known for his
Schottky diodes but he, along with an unsung
partner, Erwin Gerlach, also invented the ribbon
microphone in the early 1920s. His designs are
now used daily in the recording world, and his
diode designs are even more plentiful in high-quality electronics. By the end of the twenties,
RCA geared up to produce commercially viable
ribbon mics. Many are still in use, sound fabulous and are quite collectible.
How Do They Work?
In a ribbon microphone,
a very thin sheet of foil
is suspended in a magnetic field—very thin,
around one to two
microns thick
(.00005 inch).
The ribbons
are folded
or corrugated
anywhere from
less than 12 to
a little more
than 24 corrugations per
inch. While
it’s possible
to actually
replace the
ribbon element, I
don’t recommend you
try it—the ribbon will
likely fall apart in
your hands. Despite
that admonition,
