Other Types of Microphones
For the same ratio of direct/reverberant sound, omni-directional
microphones must be closer to the sound source than cardioid or
bi-directional microphones. Microphones should generally face
the sound source head-on; if not, treble losses due to phase loss
will result. The exception here is for large condenser micro-
phones, which often give the flattest response at an angle of about
10-20 degrees (off axis), where phase loss and diffraction effect
offset each other somewhat.
Proximity Effect and Working Distance
The Sound That Is “More Real than Real”
Ribbon microphones have long been renowned for “rich bass”.
This effect is largely due to the fact that ribbon microphones gen-
erally have excellent bass response to begin with, and at the same
time exhibit an effect known as “proximity effect” or “bass tip-
up”.
As illustrated in the following graph, a typical bi-directional rib-
bon microphone will have a flat frequency response at a distance
of about six feet from the microphone but at shorter distances the
bass response becomes boosted; the effect becomes increasingly
pronounced as the distance between the microphone and the
sound source is reduced.
This bass-boosting characteristic can become quite intense and, if
desired, can be corrected by equalization. However, for a multiple
microphone setup, the pronounced bass boosting (due to prox-
imity effect) can be turned to an advantage. If an instrument,
such as a trumpet, is extremely close-miked and the bass is cut to
restore flat response, unwanted low-frequency sounds are cut
back by upwards of 20 dB compared to an unequalized micro-
phone with a flat response. This discrimination is
independent
of
the microphone’s polar response.
Typical relationship of microphone distance to frequency response for ribbon-
velocity bi-directional microphone.
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