Recording - November 2014 - 14

A Sense Of

Direction

Interview by Mike Metlay
Photos by Fernando Curiel

of DPA Microphones
Mikkel Nymand discusses directionality
Earlier this year, Músico Pro editor Fernando
Curiel and I had a chance to visit the headquarters of DPA Microphones in Denmark. We were
treated to a fascinating tour of the facility, where
we saw how the company's many applicationspecific microphones are developed from a very
small number of finely-tuned capsule designs.
For me, the highlight of the visit was an in-house
miking clinic given by DPA Product Manager
Mikkel Nymand.
As a Tonmeister from the Royal Danish Academy
of Music in Copenhagen, Mikkel has engineered a
large number of classical projects in stellar venues,
from the Danish National Symphonic Orchestra to
an ongoing series of recordings with the New York
Philharmonic at Lincoln Center, celebrating the
150th birthday of Danish composer Carl Nielsen.
He holds several Grammy® nominations and other
international balance engineering prizes. When
he's not capturing world-class performances,
Mikkel handles communication among the many
development teams at DPA; he provides ideas,
specifications, hands-on tests, and more, helping to
bring DPA's mic designs to life.
Mikkel's clinic featured two fun demonstrations
that highlighted important facts about microphone directionality, and in a recent phone interview he expanded on these ideas with me. We'll
provide audio examples of some of the demonstrations at http://is.gd/MNymandDPAClinic for
your enjoyment; in the meantime, here's the first
of what I hope will be a number of enlightening
discussions with Mikkel.-MM
14

RECORDING November 2014

Mikkel, thanks for taking the time to talk with us. I'd like to take some of the
ideas about directionality that you communicated so well to us in your clinic at
DPA Headquarters, and put them in a form where our readers can walk away
with them and say, "This is something I can use right now."
Mikkel Nymand: Let's see if we can get there-I'm sure we can!
We hear about directionality and understand the basic idea that some mics are
designed to be more sensitive in certain directions and reject sounds coming
from others; this is often described in terms of a polar pattern. How does one
read a polar pattern chart, and what do you look for on a chart to understand
how a mic is going to behave?
If you imagine that you have a sound source in front of a microphone, and you
either make the sound source go around the microphone or turn the mic itself while
measuring the level, that is basically what is seen on a polar pattern. If we have a certain level out of the microphone at what we call 0 degrees, the on-axis input, we put
that at zero. We then draw a line around the microphone and move the line out from
the center or in toward the center as we get peaks and dips in different places.
An omnidirectional microphone's polar pattern would ideally be a perfect circle, but a
directional microphone's polar pattern will go in toward the middle at angles where there
is attenuation. The closer to the middle of the circle, the more the sound is attenuated.
So, for instance, if one were to look at a cardioid microphone's polar pattern, one
would see that at 180 degrees, right behind the mic, there is a great deal of attenuation. That indicates by looking at the pattern that sounds will be softest if you're right
behind the axis of the mic.
On a figure-8 mic you would see those dips on either side of the microphone?
Exactly. We call the bidirectional mic a "figure of 8" because the polar pattern
looks like that, with the dips that we call nulls.
How do you make a microphone directional? Does introducing directionality into
a microphone introduce sonic compromises or a change in the sound of the mic?
It certainly does. The omnidirectional microphone is what we call a pressure microphone; it reacts to sound pressure on the diaphragm and puts out a voltage. It's the simplest design and also the easiest way to make its frequency response linear. We can also
create a pressure gradient microphone, which reacts to differences in pressure between
front and back. This natively gives a figure-of-8 polar pattern. By introducing an acoustic
trap on the rear side, a structure that introduces a delay in the sound, we can create different directionalities like cardioid, supercardioid, or whatever you'd like to have. You

http://www.is.gd/MNymandDPAClinic

Recording - November 2014

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