Specifications
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Pressure Transducers
... are characterized by an omnidirectional polar pat-
tern, i.e. they pick up sound from all directions to an
(ideally) equal degree. Microphones of this type do not
have “proximity effect“ (low-frequency emphasis with
close placement to a sound source). But condenser
microphones operating on this principle can have flat
frequency response down to the lowest audible fre-
quencies, permitting full, impressive low frequency
sound reproduction. Unlike a loudspeaker, a micro-
phone's membrane size has no effect on its low-fre-
quency capabilities since it operates purely as a sensor,
like an eardrum; it doesn't have to move large volumes
of air at low frequencies as a loudspeaker must do.
For reasons of physics (capsule dimensions), the omni-
directional pattern can be maintained in its ideal form
only up through the midrange frequencies. At higher
frequencies, sounds ar riving on axis are progressively
emphasized by the inter action of the capsule housing
with the shorter wave lengths. The larger the diameter
of the housing, the greater the difference in high-fre-
quency response between on-axis and off-axis sound.
This effect can be seen clearly in the capsules’ polar
diagrams. It is the reason for their differing frequency
response in the direct versus the diffuse sound field.
When the high-frequency emphasis is corrected so
that the response measures flat on axis, the result is a
pressure transducer type such as the MK 2 or CCM 2.
These microphones are ideally suited to picking up
acoustic sources in the near field. But if a microphone
of this type is placed in the reverberant sound field,
where reflections from walls, ceiling, floor, etc. pre domi -
nate, there will be a loss of overall brilliance. These
reflections, with their high-frequency content attenu-
ated by surface absorption, reach the microphone at
oblique angles of incidence and suffer additional losses
as compared with sounds picked up directly. Here (in
the diffuse sound field, beyond the reverberation
radius*) a microphone with some high-frequency
emphasis (MK 2H, MK 2S, MK 3 or the corresponding
CCM compact microphones) is required so that at
high frequencies there will be balanced sound rather
than a rolloff. This, of course, adds brilliance to sounds
picked up at close range and on axis – an effect which
may be desired in some circumstances.
A pressure transducer with ideal response in all situ-
ations does not exist. A very small capsule could allow
the high-frequency response to be flat regardless of
direct- or diffuse-field placement, but such small cap-
sules are quite noisy. The user must therefore consider
the nature of the pickup and make an appropriate
choice. Please note that the design of of the MK 2S or
CCM 2S achieves a technically sophisticated compro-
mise between the re quirements of working in the direct
and the reverberant sound fields (in the region of the
reverberation radius).
Particularly for two- and three-micro phone stereo
pickups, which are usually made near the rever bera-
tion radius (where the direct and reverberant sound
fields are of equal level), the MK 2S and CCM 2S have
become favorites of many sound engineers. This is also
true for the MK 2H and CCM 2H, whose characteris-
tics are somewhat closer to those of the free-field mod-
els MK 2 and CCM 2.
Pressure-Gradient Transducers
Note: Usually, any directional microphone is referred
to as a “pressure-gradient transducer” even when it
has only a limited pressure-gradient component (e.g. a
cardioid). This usage is technically not quite correct,
since a true pressure gradient transducer always has a
bidirectional (figure-8) pattern. Nevertheless, we have
adopted this nearly universal practice.
SCHOEPS makes many different types of directional
cap sules and micro phones, each having specific fea-
tures and a range of typical applications.
What they all have in common, as you can see from
their polar response diagrams, is that their sensitivity
to any sound depends on the angle of incidence of that
sound; they “favor” sound that arrives from particular
directions. This allows them to maintain the same bal-
ance of direct to diffuse (reverberant) sound when
placed at a greater distance from the sound source
than an equally sensitive omnidirectional microphone.
The bidirectional MK 8 and CCM 8 are pure pres-
sure-gradient transducers. Our other directional micro-
phones use combinations of the pressure and press ure-
gradient principles; their various directional character-
istics result from differing proportions of these ingredi-
ents.
All our microphones, including the multi-pattern ones,
are single-dia phragm – a feature unique to SCHOEPS.
This results in polar patterns that are less frequency-
dependent than any dual-diaphragm design can offer,
a high-frequency response that is distinctly more
extended, and low-frequency response (with our single-
pattern omnidirectional microphones or in the omni di-
rectional setting of our multi-pattern microphones)
that is essentially perfect.
One advantage of small pressure-gradient transduc-
ers such as SCHOEPS microphones is that their direc-
tional pattern can be kept constant across a wider fre-
quency range than with a pressure transducer. On the
other hand, their low-frequency re sponse in a free
sound field is not as extended as that of a pressure
transducer. Placement in the near field can compensate
for this bass rolloff via proximity effect, but there is
also a risk of overcompensation.
Proximity effect may also be used to suppress envi-
ron mental noise by choosing a microphone type hav-
ing a large bass rolloff and / or by the use of a corre-
sponding electronic filter. A car dioid microphone at a
distance of less than 40 cm, for example, will pick up
a speaking voice quite clearly, while environmental
noise will be suppres sed due to the directivity of the
cardioid pattern and its bass rolloff. At the same time,
Principal Microphone Characteristics