NeumannBerlin Microphone MM 2 User Manual

neumann.berlin  
the microphone company  
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-  
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.  
el recorder monitored the  
output voltage of the mi-  
crophone under investiga-  
tion.  
The MM 2 was succeeded  
in 1954 by the MM 3,  
which had the same speci-  
fications, but was equipped  
with the AC 701(k) tube  
in place of the VF 14 M.  
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.  
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 Technische Bun-  
desanstalt, the German  
equivalent of National Bu-  
reau of Standards).  
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 capsule  
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  
VF 14 M.  
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.  
 

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