AKG D202, aka “The Sound Rocket”, English

Today on Vintage Friday we’re going to talk about an odd one out. Well, actually there is more than one, because there was a series of microphones with this design.

We’re talking about the AKG D202. The special thing about the design of the AKG D202 is that it is a so-called two-way microphone. This means that there are two membranes in the microphone. One for the high frequencies and one for the low frequencies.

Why did AKG design this microphone?

This has to do with the working principle of a so-called directional microphone. Directionality of a microphone indicates from which side it accepts sound and from which side it more or less rejects sound. This microphone has a cardioid directionality, which briefly means that it records the sound at the front, but is much less sensitive at the rear. A side effect of a cardioid recording pattern is if you are close to the microphone, the sound has a much higher amount of low frequencies than from a slightly greater distance. This is called the “proximity effect”. You can sometimes use that phenomenon intentionally, but it can also be quite disturbing.

Back to the AKG D202. It has a membrane at the front of the microphone that records the high frequencies, and at the rear it has a membrane with an acoustic chamber for the low frequencies. To ensure that the correct signal comes from the correct membrane, there is a so-called x-over filter in the microphone housing. This ensures the frequency distribution of both membranes and combines it into a full-range signal. This x-over point is at 800Hz. Which means that the membrane at the rear of the microphone that provides the low frequencies does so from 20Hz to 800Hz, while the membrane at the front of the microphone provides the high frequency range between 800Hz and 20000Hz.

So what about the proximity effect? Well, as I wrote earlier, the proximity effect occurs close to the capsule of a directional microphone. However, because the diaphragm for the low frequencies is at the back of the microphone, the proximity effect is eliminated, and therefore also the excessive build-up of low frequencies that it causes.

AKG had designed a microphone in 1967 that cleverly avoided the proximity effect, and had a more even frequency response.

The AKG D202 was widely used by artists and is still being used in the British Parliament at the moment.

As said earlier, AKG had developed a series of these microphones. They were designed by Ernst Pless, who was one of the two founders of AKG.

Other models included the D200, D222, D224 and the D900c which was designed for the film industry.

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Next week: another microphone from my collection in this blog.

See you next Vintage Friday!