ONTRACK
All Hear This: Omni-directional Mics
This month we’re going to talk about phones is to combine them with a cardioid
recording with omni microphones. Often type. When recording Al DiMeola playing
ignored due to their wide polar pattern his late-thirties Martin, I often used a pair
and general misinformation, their use in of cardioid Schoeps in an XY configuration
capturing great guitar sounds should not
be overlooked. Let’s first examine what
omni means and then see how their application might help you cut better tracks.
Omni-directional microphones capture sound
in a 360-degree pattern. Unlike cardioid,
supercardioid or figure 8 microphones, it’s
equally sensitive to sound from all directions.
Sometimes called “pressure microphones,”
omni mics measure sound pressure at a
fixed point in space. Since it’s not concerned with direction, an omni can often
be placed where other types would not
work. Also, many omni microphones (such
as DPA and Earthworks) have very small
capsules that are amazingly natural sounding with an even frequency response curve
(the DPA 4007 is virtually flat from 20Hz to
well above 20kHz). In reality, the commonly
used cardioid microphone is completely
coloring your sound – which may or may
not be right for your application.
In addition, omni microphones don’t suffer
from proximity effect, which is the boosting
of low frequencies as you get closer to the
source. They can also handle some huge
sound pressure levels, or SPLs, with certain
models taking up to 155dB before overloading. While most of us will never record
anything that loud, they can take it when
you deliver it.
So now that you have some basic fun facts
about omnis, how can you use them? Well,
since they record equally in all directions,
placing one on an acoustic guitar will also
capture some of the room sound, for example. That in turn leads to a more natural
sounding recording of the instrument. Of
course, the better the room, the better the
overall sound.
Often, when I use my Earthworks QTC- 1
[now renamed the QTC40] mic on a guitar,
the playback comments are along the lines
of “now that’s what my guitar sounds like
to me!” To an engineer capturing an acoustic instrument, that’s music to my ears.
Another great application of omni micro-
Omni-directional microphones, like Earthworks’
QTC40, can capture the subilties of a track with
super-flat frequency response and low noise
directly in front of the guitar, with another
pair of the above mentioned Earthworks
omnis just outside the Schoeps, about two
to three feet away and four feet apart.
The Schoeps provided the closeness and
tight sound while the Earthworks delivered
the ambient, open sound. By adjusting the
fader volumes of each pair and panning
them creatively on the console, the true
tone of the instrument was captured – with
very little EQ’ing.
You don’t have to use pairs of mics to get
a great sound with an omni. I often record
flamenco guitarist Romero using a single
Earthworks and a Royer ribbon mic. The
Earthworks is placed near the 12th fret of
his instrument, with the Royer capturing
the body of the guitar. This combination
yields a dark, warm tone from the Royer
and a bright, transient sound from the
Earthworks. Also, the snap of the instrument is captured in the room (which is
mostly wood) by both the figure- 8 pattern
of the Royer and the omni pattern of the
Earthworks.
Omni microphones also sound great on
things like acoustic bass, piano, strings
and as room microphones for percussion
and drums. I’ve used them to re-record
submixed string sections in a live studio by
pumping the mix of strings into the room
through speakers and mic’ing them. This
provides a dimensional sound that cannot
be duplicated by the actual close miking of
the instruments themselves.
High-end omni microphones are often used
to capture symphonic performances, since
they properly translate the ambient sound
of acoustic venues. I’ve even used them
with great results to capture vocals – with
the use of a pop screen, of course.
While omni microphones have many applications, it’s their use on acoustic guitars
that keeps me coming back for more. With
their ability to capture a clean, clear tone,
a wide dynamic range and the natural
sound of an instrument, they make a great
choice when you’re looking for something
different in the studio.
Rich Tozzoli
is a producer, engineer and mixer who has worked with
artists ranging from Al DiMeola to David Bowie. A lifelong guitarist, he’s also the author of Pro Tools Surround
Sound Mixing and composes for such networks as
Discovery Channel, Nickelodeon and National Geographic.
