Sennheiser MD-21 (1954)
The short, stubby omnidirectional dynamic that put the Sennheiser name on a microphone for the first time, and that broadcasters refused to let die.
Overview
The MD-21 is not a pretty microphone. It is short, stubby and fat, and it looks like a product of the mid-1950s. It carried the Sennheiser name out into the world, and it did that by being rugged and reliable in a way broadcasters of the period badly needed.
The MD-21 was introduced in 1954, according to a company history. It was reportedly the first product to bear the Sennheiser name instead of the earlier Labor W branding, which had become awkward as the company moved from laboratory work toward manufacturing. The same history says the MD-21 was developed as a reporter microphone and has had continuing success, remaining a current product decades after its introduction. A dynamic mic designed in the early 1950s was still being catalogued and sold into the 1990s.
The design brief, as later recounted by Sennheiser UK's John Willett in Studio-Sound (May 2000, p.92), was simple. Broadcasters wanted a rugged, reliable microphone for a wide range of uses, and the MD-21 covered enough of them that it stayed in production long after most of its contemporaries had left the catalogues. Willett is candid about the trade-off. The MD-21 is expensive in relative terms today because of old-fashioned production methods, and he quotes Rupert Neve calling it the best interview mic around. That combination of costly to make and liked by the people who used it explains why the mic endured, and why it eventually became a niche product instead of a volume seller.
The omnidirectional pattern is the key to the MD-21. An omni dynamic does not reject the room the way a cardioid does. It also has no proximity effect, so it does not thicken up when you work close, and it picks up a natural, uncolored picture of whatever is in front of it. For interview work, where the subject may not hold a steady distance and the room is whatever room you happen to be standing in, that is a real advantage. The reviewer also ran into hum until discovering that the screened mic lead was not earthed to the appropriate connector pin.
The published specifications from the period are modest but specific. A 1964 trade notice listed the MD-21 in low, medium and high impedance versions, with a claimed response from 50 c/s to 15 Kc/s rising slowly by 5 dB above 1 Kc/s. The dimensions were given as approximately 43 x 2 x 2 ins, and the list price at that time was £16 12s, distributed in the UK by Impectron Limited. The impedance versions matter today. The low-impedance version will work into a modern preamp without drama, while the high-impedance version wants a different input load and will sound wrong into the wrong thing. Check which version you are getting before assuming it will behave.
The MD-21's place in the Sennheiser line is documented in the same 1993 company history. It was followed by the MD 82 shotgun microphone in 1956, the first wireless microphone systems in 1958, and the MD 421 dynamic microphone in 1960, a cardioid design that, according to the same history, had sold 350,000 units by the time of writing. The MD-21 is the omnidirectional starting point of that lineage. A later Sennheiser company document credits founder Fritz Sennheiser with bringing the MD 2 and MD 21 microphones to market as part of a long list of watershed products.
According to the available documentation, the MD-21 has no confirmed end-of-production year, no documented set of common failure modes and no reliable current market pricing. Anyone buying one should assume the usual risks of a decades-old dynamic - a stiff or noisy switch, a connector that needs attention, a capsule that may or may not still be at spec - without treating any of that as documented fact. The 1961 review's hum note shows that earthing and cabling issues come with gear this old.
The MD-21 is not a collector's trophy in the way some ribbon microphones are. It is a working tool that happened to become a classic, and its continued existence is tied to the continued existence of the practices it was built for — broadcast interviews, reporting, and any situation where a rugged omni dynamic is the right answer. Willett's 2000 piece makes the case plainly: the MD-21 survived because it succeeded at enough of what it was designed to do that it is still around to do a more limited number of those things today. That is a better fate than most microphones from 1954 can claim.
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