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 generally 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 ribbon 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
proximity 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 20dB compared to an unequalized microphone 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 bidirectional
microphone.
Another area where proximity effect can be turned to an advantage is to make things sound more
“real than real.” For example, many voices and certain musical instruments produce fundamental
frequencies within the bass range (below 150Hz or so) but the fundamentals are weak. If a
microphone that has no proximity effect and a rising high frequency response is used on an
upright piano, or on a person with a thin, weak voice, the recorded sound is likely to sound even
thinner than it was in real life. In contrast, using a microphone with strong proximity effect on
such sound sources can deliver a “better than real” sound, since the boosted bass response will
compensate for the weak fundamentals in the sound source. Since the fundamentals are present,
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