Winding a Pleiades filter on Siemens Epcos core for using on AKG D112 for vocals

200 turns on the black ferrite Siemens Epcos core that just fits inside an XLR male to female barrel produced an inductance of 86mH. The insulated enameled wire diameter was 0.1mm and filled almost one complete layer.


This can be just about right for using in parallel with an AKG D112 for great vocals at 4in (bass proximity compensation) or in other words passive eqing. So the inductor is just connected to pins 2 and 3 inside the barrel and everything is nice and balanced.


On a Magnetec 073 core much less turns are needed for the same inductance.


The wire resistance should play a part too as it will shelve out the bass reduction at some low turnover frequency. (The coil reactance at 0Hz is 0ohms but we are left with the resistance of the wire).


Apparently a variable resistance is used in series with an inductor and the whole lot in parallel with the mic output on the Sennheiser MD421 to give variable bass cut slopes.

A way to connect the Sennheiser MD421 HN HL or MD21 HN HL balanced without modifying it

We just assume it is balanced and it may be.


The good news is that the center pin of the microphone is not connected to the metal part of the microphone.


So a cable can be made as follows:


A male Neutrik connector is connected  to a balanced twisted pair cable the normal way. X L R (external live return) ie 1 2 3.


On the other side of the cable:


The central mini Female Tuchel pin is connected to cable return. The live cable is connected normally to the low impedance Tuchel pin.


And the external screen of the cable is connected to the metal part of the mini Tuchel only.


The internal shunt autotrasformer? is a good thing as it electromagnetically damps extremely low frequencies, pop and wind.

iPad low cut filter on GarageBand audio recorder

A -3dB point was measured at around 250Hz. Lower frequencies than this seem to be greatly attenuated as seen on the Garagebands VU meter. Response at High frequencies was great 3dB at around 20KHz.


On the sampler of GarageBand the LC seems a bit more gentle.


Would the amazing engineers behind iPad and GarageBand add a switch to full bandwidth?


The inherent low cut can be useful for proximity compensation.


Fewer options force creativity, in the meantime one could record on sampler a high note of an instrument and play the low notes on the sampler keyboard. This works even on high pitch oscillators recorded by microphone or direct as on this setup. 10KHz tone recording gave great bass and mid notes as there was some kind of interesting distortion.


Setup:


Test tone CD - Sony D-EJ758CK CD player - Canford red Neutrik impedance converter 1/4in jack - Pleiades K117 - iPad mini

Could this have been recorded with MD21?

Rudi Carell can be seen on the MD21 instructions using the mic in his TV show.


A great singing video can be seen including Esther Ofarim:
https://m.youtube.com/watch?v=uGFeKdwJIb8


Have they sang using an MD21?

STC 4021 microphone

There is an amazing demonstration of 4021 by Martin Mitchell on YouTube.


https://m.youtube.com/watch?v=zXICfcS1fd0

Sennheiser MD21 vocals

It can be seen on YouTube, Steve Winwood Spencer Davies Group:


https://m.youtube.com/watch?v=TG32gmIIsVo


It is a great omnidirectional microphone so it exhibits no proximity bass boost effect.


The link was found on Martin Mitchells's microphone website.

How to convert an AKG D112 to a great vocal microphone without modifying it

An easy way is to connect to it a Pleiades filter.


This is an inductor in parallel with the signal out (ie voice coil).


An inductance of 47mH to 82mH should be great.


It can all be fitted inside an XLR male to female adaptor, more information on previous euroelectron posts.


The magnetic core used can be a Magnetec 073 or an Epcos Siemens ferrite etc.


These filters will also electromagnetically damp pops.


The AKG D112 is an interesting candidate as its frequency response has similarity with Neumann U47. The sound on voice is extremely natural.


More information on how to make these on older and newer euroelectron posts.