What an amazing company.
It is a small unassuming looking omnidirectional microphone.
It was decided to give it a try. There was no sign of life. After sweating atempts of opening without destroying, it survived opening.
Learning the hard way... If the plastic ring is removed without destroying it...And only if needed there is a screw on the back of the capsule, full of solder. Using desoldering braid one may be able to release this screw. If this screw is released the circuit board is loose and the voice coil ends are very vulnerable to be cut. There are extremely thin.
There was no sign of continuity on the voice coil. It was decided to glue two wire wrap wires on the voice coil output rails. And then trying to solder them to the extremely thin voice coil wires near to where they exist the membrane. The soldering iron had to melt solder, and at the same time melt the enamel insulation while some plastic of the housing was melting too! After a few atempts by trying to get all these happen together by chance, the miracle happened. It still cannot be believed it works!
The voice coil wire is extremely thin. How do they wind such a thin wire? Almost invisible to naked eye. The DC resistance is a bit less than 800Ω!
Immediately connecting to the Pleiades V4 pre preamplifier there was a very detailed sound. And outdoor ambience high frequency detail could be heard in an uncanny realistic way.
It was observed again that the unbalanced connection polarity made a difference in sound. The capsule was connected by crocodile clips to the primary of the inline 1/4in jack transformer. One way bass and no detail. The correct way was lifelike and clean.
There was a lot of sibilant sensitivity problems.
All these disappeared when the acoustic resistance was connected to the back of the capsule firstly held by hand.
The moving coil capsule is very beautiful with almost orange colors.
The acoustic resistance seems to be the back circuit board itself. It is the size of the diaphragm. It has 8 holes and a white thin felt glued on the other side. The felt is to touch the back of the capsule. Then the screw at the center holds the acoustic resistor (circuit board) in place and one can connect there the voice coil ends and the microphone cable.
The acoustic resistance has a tremendous effect on sound.
By just placing it by hand while speaking or singing in front of the capsule all the muddy bass disappears. The nasty "s" problems disappear. And the sound becomes instantly world class. Focused with smooth midrange and great detail.
This is perhaps what textbook refer to... That moving coil microphones are tuned to mid band. The acoustic resistance damps the reasonance converting a peaky curve of low bandwidth to a shorter curve of larger bandwidth.
When the microphone was closed and ready the sound was amazing.
One could hear every detail of bird sounds even with windows closed. Hiss almost absent. And every detail was magnified by the Pleiades V4 battery powered electron tube pre preamplifier of ultra low noise.
Whereas there is almost absence of hiss making you wonder whether the setup is on, when speaking or singing near the microphone a very full and smooth dynamic sound comes out of this world class microphone.
The sound is there, no Pleiades filters needed to making it sound correct to mind perception. Frequency response seems, sounds, is perceived to be flat from vocal chords of singer to the brain of the listener.
Setup (signal path):
Male voice - MD611 M - inline 500Ω to 50KΩ input transformer of 300mH primary inductance - Pleiades V4 with EF183 powered by 3.6V battery - Realistic disco mixer connected at mic input - Sennheiser HD 580 - listener
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