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This is what provides the directional characteristics of a cardioid microphone,
in that it will pick up at the front and the sides and picks up far less at the rear,
therefore making the microphone directional. However, this is textbook theory.
This is much different in practice with real (imperfect) microphones used in the
real world.
(9b) Conventional Cardioid Microphone
Figure 9. Differences in the Rear Polar Response Between a Perfect,
Conventional and an Earthworks Cardioid Microphone
Figure 9b shows the polar response of a typical conventional cardioid micro-
phone. Notice at 500Hz, 1kHz and 4kHz the pick-up pattern is almost an omni
pattern, however, these three frequencies are down 10dB in level in reference
to their level at the front of the microphone (0 degrees). In contrast 16kHz and
20kHz are down 15dB at the rear of the microphone. We need to look at one
important fact. Which frequencies are most audible, 500Hz to 4kHz, or 16kHz
to 20kHz? Without question the frequencies between 500Hz and 4kHz are
vastly more audible or predominant than those between 16kHz and 20kHz.
This shows that the typical conventional microphone in Figure 9b will be some-
what less sensitive at the rear of the microphone, but by only about 10dB in the
frequency range between 500Hz and 4kHz.
Looking at the Earthworks cardioid polar response in Figure 9c shows that it
has far more rejection in 500Hz to 4kHz frequency range at the rear, than the
conventional microphone shown in Figure 9b. In Figure 9c, see that 1kHz is
down by 30dB or more, while 500Hz and 4kHz are down 15dB. Also notice that
16kHz and 20kHz are only down 5dB to 10dB. But remember that these high
frequencies are far less audible than those between 500Hz and 4kHz.
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(9a) Textbook Perfect
Cardioid Microphone
(9c) Earthworks Cardioid Microphone
What we have reviewed so far is technical information shown on charts and
graphs. Now lets look at what happens in the actual use and application of these
two types of cardioid microphones. If you were to take the typical conventional
cardioid microphone in your hand and talk into the front of the mic and while
you are talking, rotate the microphone 180 degrees and talk into the rear of the
microphone, you would notice some reduction in the audible level of your voice.
In contrast, if you were to do the same exercise with an Earthworks cardioid
microphone, when you started talking into the rear of the microphone your voice
would be nearly inaudible. This practical demonstration shows how dead the
Earthworks cardioid microphones are at the rear. As a general guideline, you
can consider the coverage area from 90º, 180º to 270º the dead zone of an
Earthworks cardioid microphone as illustrated in Figure 10.
Figure 10. Rear Polar Response of an Earthworks Cardioid Microphone
When miking choirs with an orchestra or band in front of the choir, the rear
rejection of sounds from an Earthworks cardioid can be a real benefit. When
positioning the Earthworks microphone, make sure that the rear of the capsule
is facing the direction of the orchestra or band as shown in Figure 11.
Figure 11. Proper Positioning of an Earthworks Cardioid Microphone
with an Orchestra or Band behind the Microphone
Correct
- microphone
head perpendicular
to floor for maximum
isolation from the
orchestra or band
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