I posted in the other equipment forum a post asking if anyone knew anything about the AKG D202 mic. I just got some info from AKG about this mic and found it very interesting so I thought I'd share it all with you.
"The D202 was a dynamic cardioide twoway microphone. The twoway mic technique
was a patented innovation of AKG. Such microphones incorporated two separate
capsules. One was for bass/midrange the other covered the high audio
frequencies. The reason for this design was that the complete audio
frequency range the human ear can hear is over ten octaves wide. A dynamic
directivity microphone with it´s relatively high moving mass of the
diaphragm with voice coil can only be designed to work perfectly within a
certain limited area within this range. Outside this area the design
engineers have to find suitable compromises. In other words, an ideal
microphone for best high frequency reproduction shall be as small as
possible to avoid undesired partial movements of the diaphragm and to ensure
frequency stability of the cardioide. Such a microphone would not perform
very well at low frequencies as it would have problems to convert the high
energy at heavy bass sounds. Contrary an ideal bass transducer would be much
too large for exact treble reproduction. A condenser mic does not have such
problems as the diaphragm is very thin and light, has no heavy voice coil to
move and can be designed to give best bass response as well. Disadvantage is
that a condenser mic is more expensive due to the more complicated design,
needs external powering, has certain limits regarding climate conditions and
sometimes is much more sensitive to rough handling".
"To create a microphone having a similar sound as a condenser mic but with
all advantages a dynamic mic has the two way technique was the ideal
solution. Similar as with loudspeakers not only one capsule is used but two
as you´ll find at least a woofer and a tweeter in most better loudspeakers.
The two capsules are of course combined by a carefully designed crossover
network. Another unique feature could be achieved by this two way technique
and this is an almost total lack of proximity effect. This effect causes a
more or less significant boost of bass the closer the mic is brought to the
sound source and is inherent in every normal directivity microphone. With a
two way microphone no such effect is present and the sound reproduction
remains the same not regarding on how far away you are setting up the
microphone to the source of sound. This could be reached by making
individual rear sound ports for the bass and for the treble system. In every
directivity microphone both sides of the diaphragm are exposed to the sound
field. So, the diaphragm is moved by the sound pressure difference between
front and rear side. This means that all such mics have a front and a rear
sound port usually covered by the mics top cap. To avoid the proximity
effect it is necessary to extend the distance between the two ports as much
as possible. Therefore the rear sound port for the bass system is via slots
at the connector end of the microphone. The D202 was designed in about
1967/68 and produced for many years as a superb dynamic microphone. As
during the years ordinary dynamic microphones have been more and more
improved and condenser microphones have become cheaper, the market for such
a special microphone has become smaller and this is the reason why at least
at the moment AKG does not continue this special design".
"The twoway mic range consisted of the D202 in various versions (D202E1 being
the studio version), the D224 which was a slim line variation mainly for TV
and film applications and the D200, a less costly twoway mic for home
recording. Later came a mic called D222 which was similar to the D202 but
reduced in size".
"From the application it can be said that the D202 was used for high quality
recording of music instruments and speech without any tonal coloration.
Especially the fact that it had no proximity effect made it best suitable
for speech recording in broadcasting studios (radio narrators, announcers,
interviews, etc). It was not so popular as a hand held mic for singers on
stage as the lack of proximity effect is not desired in such applications".
"The version D202E1 carried a three position switch allowing the settings 0
dB, -7 dB and -20 dB at 50 Hz".
"Output of the mic signal is via a balanced 3 pin XLR connection. For using
the mic on unbalanced inputs it is absolutely necessary to connect pin 1 to
pin 3 and to the cable shield. This can be done inside the cable connector.
Pin 2 carries the "hot" output signal".
"The D202 was a dynamic cardioide twoway microphone. The twoway mic technique
was a patented innovation of AKG. Such microphones incorporated two separate
capsules. One was for bass/midrange the other covered the high audio
frequencies. The reason for this design was that the complete audio
frequency range the human ear can hear is over ten octaves wide. A dynamic
directivity microphone with it´s relatively high moving mass of the
diaphragm with voice coil can only be designed to work perfectly within a
certain limited area within this range. Outside this area the design
engineers have to find suitable compromises. In other words, an ideal
microphone for best high frequency reproduction shall be as small as
possible to avoid undesired partial movements of the diaphragm and to ensure
frequency stability of the cardioide. Such a microphone would not perform
very well at low frequencies as it would have problems to convert the high
energy at heavy bass sounds. Contrary an ideal bass transducer would be much
too large for exact treble reproduction. A condenser mic does not have such
problems as the diaphragm is very thin and light, has no heavy voice coil to
move and can be designed to give best bass response as well. Disadvantage is
that a condenser mic is more expensive due to the more complicated design,
needs external powering, has certain limits regarding climate conditions and
sometimes is much more sensitive to rough handling".
"To create a microphone having a similar sound as a condenser mic but with
all advantages a dynamic mic has the two way technique was the ideal
solution. Similar as with loudspeakers not only one capsule is used but two
as you´ll find at least a woofer and a tweeter in most better loudspeakers.
The two capsules are of course combined by a carefully designed crossover
network. Another unique feature could be achieved by this two way technique
and this is an almost total lack of proximity effect. This effect causes a
more or less significant boost of bass the closer the mic is brought to the
sound source and is inherent in every normal directivity microphone. With a
two way microphone no such effect is present and the sound reproduction
remains the same not regarding on how far away you are setting up the
microphone to the source of sound. This could be reached by making
individual rear sound ports for the bass and for the treble system. In every
directivity microphone both sides of the diaphragm are exposed to the sound
field. So, the diaphragm is moved by the sound pressure difference between
front and rear side. This means that all such mics have a front and a rear
sound port usually covered by the mics top cap. To avoid the proximity
effect it is necessary to extend the distance between the two ports as much
as possible. Therefore the rear sound port for the bass system is via slots
at the connector end of the microphone. The D202 was designed in about
1967/68 and produced for many years as a superb dynamic microphone. As
during the years ordinary dynamic microphones have been more and more
improved and condenser microphones have become cheaper, the market for such
a special microphone has become smaller and this is the reason why at least
at the moment AKG does not continue this special design".
"The twoway mic range consisted of the D202 in various versions (D202E1 being
the studio version), the D224 which was a slim line variation mainly for TV
and film applications and the D200, a less costly twoway mic for home
recording. Later came a mic called D222 which was similar to the D202 but
reduced in size".
"From the application it can be said that the D202 was used for high quality
recording of music instruments and speech without any tonal coloration.
Especially the fact that it had no proximity effect made it best suitable
for speech recording in broadcasting studios (radio narrators, announcers,
interviews, etc). It was not so popular as a hand held mic for singers on
stage as the lack of proximity effect is not desired in such applications".
"The version D202E1 carried a three position switch allowing the settings 0
dB, -7 dB and -20 dB at 50 Hz".
"Output of the mic signal is via a balanced 3 pin XLR connection. For using
the mic on unbalanced inputs it is absolutely necessary to connect pin 1 to
pin 3 and to the cable shield. This can be done inside the cable connector.
Pin 2 carries the "hot" output signal".