The cartridge
Types 4004 and 4007 are omnidirectional (pressure) microphones which
use a 12mm diameter prepolarized condenser cartridge. The diaphragm is a
nickel foil which has been coated with an ultra-thin polymer layer for
optimum corrosion resistance. The microphone housing is of German silver,
an alloy with a high content of nickel to match the stable thermal qualities
of the diaphragm. The self noise of the cartridge is typical 24dB(A) re. 20µPa
and the nominal sensitivity of the Types 4004 and 4007 are 10mV/Pa and
2.5mV/Pa respectively. Due to the size of the cartridge it can handle
extremely high SPLs, has an extended linear frequency response up to
40kHz and a high degree of omnidirectionality, even for higher frequencies.
For optimum stability the microphone cartridges have undergone a special
pre-aging process which releases all tensions in the materials and stabilizes
the polarization voltage.
The preamplifier
Types 4004 and 4007 are acoustically identical, but differ in their
preamplifier powering system. The 4004 is powered with 130V via the
HMA4000 Two-Channel High-Voltage Microphone Amplifier and has a
modified 3-pin XLR-connector (see Fig. 1 for pin designation). This special
powering system enables the microphone preamplifier to handle
approximately 10dB higher SPL than similar microphone types powered
through conventional P48 systems (4004: 168dB SPL peak and 4007: 155dB
SPL peak). Furthermore, the 4004 together with the HMA4000 is a totally
tranformerless system and therefore has an extended low-frequency
handling capability (10Hz to 40kHz ± 2dB). The 4007 is powered via a
standard P48 system and is equipped with a high quality audio transformer
and a standard 3-pin XLR-connector (see Fig. 2 for pin designation). Types
4004 and 4007 use state of the art low-noise preamplifier technology and
are driven with unity gain.
2
Technical Description
User’s Manual
