Royer R-122V User's Guide download pdf (Page 12)

3. Variation in ratio of direct to reverberant sound. Tendency of a microphone to favor the

nearest sound source due to a combination of these items, plus the inﬂuence of the inverse

square law. The inverse square law states that for each halving of source-to-microphone

distance, the sound pressure level quadruples.

Other Types of Microphones

For the same ratio of direct to 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 cancellation can result. The exception

here is for large diaphragm condenser microphones, 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 generally have excellent bass response to begin with, and at the same

time exhibit an effect known as proximity effect.

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.

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

!12

Typical relationship of microphone distance

to frequency response for ribbon-velocity

bidirectional microphone.

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Royer R-122V User's Guide Page 12