Fostex M20RP Mid Side MS Microphone with Pleiades (R,L) Filters, comparison with Shure SM63

Signal path:


Ambience or male singing voice - Fostex M20RP - Fostex P400 Matrix Box MS to L R matrix transformers = Pleiades (R,L) Filters - Sony TC-D5 Pro = Sennheiser HD580


= denotes 2 cables (2 transmission lines) (2 channels)


(Before feeding Sony TC-D5 Pro both channels were phase inverted by x(-1) XLR female to male adapters. Ie pin 2 in connected to pin 3 out etc)


Very natural sound at ambience.


As expected somewhat bass heavy sound the closer the distance since mic elements are directional. A cardioid for Mid and figure of 8 for Side. A sensitive microphone.


By connecting Pleiades filters of 330mH the sound clears up substantially and mic can be used for singing at a small distance. Signal of course increases even more. Perhaps a series resistor is needed too, (R,L) filter, for a gentler slope.


Removing the P400 transformer and connecting the Mid microphone capsule only to Pleiades filter Sony bridged mono etc produces a louder sound.


Connecting a Pleiades (130Ω,40mH) makes for a very interesting bright sound.


In comparison the simple and great Shure SM63 moving coil omnidirectional microphone sounds louder but a bit bass heavy and treble heavy. With a 330mH Pleiades inductor filter treble heavy, nice and interesting but artificiality in mid high frequency band can be heard.


The Fostex M20RP gives less output, so gain must be increased on the Sony preamp, but sound is smooth and natural no matter whether connected to a Pleiades filter or not. Perhaps not the most neutral sound but with impressive neutrality.



With Pleiades (R,L) filters it approaches the ideal of flat frequency response from producers brain to singers brain [Lowe, Morgan]. No s, or p problems.


Reference:


Sound Picture Recording and Reproducing Characteristics - D. P. Lowe, K. F. Morgan - Journal of the Society of Motion Picture Engineers