Neumann.Berlin MM 5 User's Manual
Contents
1. yr yw J f N NEUMANN BERLI gt gt THE MICROPHONE COMPANY Calibration Microphones MM 2 MM 3 MM 5 As an audio pioneer Neumann is constantly charting new terri tory In the early years when microphone production was still in its infancy new problems were encountered at nearly eve ry turn For example how can a thin diaphragm be produced from plastic Neumann solved this particular problem by heat ing the plastic and pouring a con trolled amount onto the surface of water For the very first microphone amplifiers resistors were fash ioned from thin bars of graphite Acoustic measuring devices hardly existed So Neumann de veloped the first practical loga rithmic level recorder For the absolute calibration of pressure microphones Neumann de signed a pistonphone In the best pioneering tradition Neumann used these devices as indispen sable tools and aids for explor ing the frontiers of acoustic re search and the realization of in novative ideas The industry also lacked a cali bration standard for the acous tic testing of microphones In 1949 Neumann developed a miniature microphone capsule that functioned as a pressure transducer The aluminum mem brane measures 10 mm in diam eter To prevent disturbing the sound field in the calibration room by the relatively large mi crophone amplifier the caps2. nische Bun desanstalt the German equivalent of National Bu reau of Standards Just as Neumann level recorders were standard equipment in most acous tic calibration laboratories of the time Neumann calibration microphones served for decades as the standard for nearly all manufacturers of microphones and loudspeakers Calibra tion microphones continued to be produced until the ear ly 1970s Today almost thirty years later many of them are still in service D D a gg
3. ule assembly is separated from the amplifier housing with electri cal connection running through a thin tube of 25 cm length The amplifier is modified from the electronics used in the U 47 with the same tube model VE 14 M O we Ro The calibration microphone features a linear frequency range of 20 16 000 Hz with a maximum deviation of 1 dB Neumann used the calibration microphone in conjunction with two Neumann P2 level recorders for qual ity control of its own microphone production The combi nation of the calibration microphone with one level record er served to maintain a constant sound pressure level in the calibration room independent of the frequency The second lev el recorder monitored the output voltage of the mi crophone under investiga tion The MM 2 was succeeded in 1954 by the MM3 which had the same speci fications but was equipped with the AC 701 k tube in place of the VF 14 M For detecting higher fre quencies up to 50 kHz for example when testing acoustic models in reduced scale Neumann developed an even smaller capsule with a Nickel diaphragm known as the MM 5 Introduced in 1955 the MM 5 s frequency response up to 20 kHz is as consistent as that of the MM 2 and MM 3 In the 20 kHz to 50 kHz range the tol erance is less than 3 dB These close tolerances were regularly checked in cooperation with the Nat ural Metrology Institute in Braunschweig now Phy sikalisch Tech
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