This is the MD441 type without the low cut filter.
Various cut off frequencies of Pleiades filter were tried in an attempt to:
1. Use the mic at 0in.
2. Use it for singing a type of song such as the beautiful with beautiful vocal: Going to a Town - George Michael:
https://m.youtube.com/watch?v=8DZJQjn3jV8
Phil Ramone can be seen producing.
(Is the microphone used on this song the SKM 5200 with the Neumann KK 104 condenser capsule?)
Firstly (while singing this song for this experiment) a Beyer M 55 was tried without any Pleiades filter. It sounded very nice but bass heavy. It seems singing voice needs less bandwidth than speech to sound correct to our brain.
Then the MD441 U3 was connected directly and as expected at 0in the sound was eeeeexxxxxxxtremely bass heavy due to the proximity effect. This is good news as when the right Pleiades filter is applied, making the voice sound correct, all background far off noise and ambience will be out. This is a very effective noise canceling principle invented so many years ago.
The 0-1in distance capability is very useful too as you can see George Micahel performing live while recording at the Air Studios Lyndhurst (church) near the full orchestra without wearing headphones, if the master take happened this way.
The cutoff 6dB per octave frequency in the setup used is already 70Hz because of the parallel inductance of the Canford input transformer which has a primary inductance of 400mH.
Then a Pleiades inline XLR filter of 600Hz was connected after a 375Hz ie 975Hz. The sound was almost there close to the timbre.
Then a Pleiades filter of 1.27KHz (25mH) was connected, it sounded fantastic but perhaps a bit thin
as expected.
So a 100Hz Pleiades filter was connected to the previous setup making a cutoff frequency of 70Hz + 975Hz + 100Hz, roughly 1140Hz.
It sounded fantastic and almost right for this type of song and next to mic distance. At such small distance the output of the microphone is very high too making an added advantage.
The MD441 is a fantastic microphone. There wasn't the slightest "s" sibilant problem even at 0in while the voice of course was crystal bright and there was not the slightest background acoustic noise capture or any other noise like hiss. Pop was absent too due to,the excellent mic and the sampling of the voice coil at the low frequencies by the Pleiades filter.
Setup, signal path:
Male voice singing Going to a town at the original key - MD441 U3 at 0-1 inch - Pleiades 1070Hz - Canford 70Hz (400mH input transformer) - Pleiades V4, EF183 electron tube operating at 3.4 volts - Realistic disco mixer at mono mic in - Sennheiser HD580
The overall cutoff frequency indicates that the inductance needed to be connected to the mic is 27mH.
Why?
Because 200Ω divided by 2 divided by π=3.14 divided by 1140Hz makes 27mH.
It should be very easy to make such a Pleiades filter as the inductance needed is so low. With a Magnetec 073 core it should be just a few turns and everything can fit inside an XLR inline female to male adapter. The coil is connected to pins 2 and 3.
Or a Pleiades stepup transformer can be made with a few primary winding turns on such or bigger core. This makes easy to wind the secondary which can make a very high turn ratio in just 1-2 hours winding by hand.
The simplicity and quality becomes a joy.
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