Creating an amazing singing sound with the Sennheiser MD21 HN

It is one of the best microphones in the world.


There is no excuse not having a world class sound out of this amazing microphone with the minimum signal path.


This concentrates on how it can be connected to a Sony TC-D5 Pro or Uher 4200 report (Uher not tried yet).


The signal path:


male singing voice at 1-4in - Sennheiser MD21 or HN - R,L Pleiades filter - 1:2 step up transformer - Sony TC-D5 Pro XLR mic in mono - Sennheiser HD580


The first wave filter is an inductor in series with a resitor and the resultant connected in parallel with mic out or voice coil. It is a gentle slope, less than 6dB per octave, low cut filter. The values of the XLR barrel Pleiades filter used are 130Ω, 40mH. This is more or less a random choice that gave a good sound. The values have to be adjusted according to application. What is this filter doing? It removes bass heaviness due to equal loudness curves and voice effort curves [Lowe, Morgan].


Next in the signal path is a 1:2 transformer. It transforms the 200Ω mic impedance to 800Ω so that the Sony can be generously driven by this passive mic booster amplifier. The D163851 Western Electric transformer was used which has a primary inductance of 1H. So it does only a slight bass cut below 35Hz? and perhaps some high frequency taming so that the end result is natural to listeners brain [Lowe, Morgan].


The same signal path was also used with great results on the Paso M8 cardioid microphone after removing the series low cut capacitor, which is a difficult mic for getting a high s/n ratio.


So with MD 21 it is a walk in the park. A so big, low noise, natural sound with nothing else than 2 passive filters between mic and recorder.


Reference:


(Flat frequency response from producer's brain to listener's brain), Sound Picture Recording and Reproducing Characteristics - Journal of the Society of Motion Picture Engineers