Comparison between Unidyne III and SM58 Mexico

Unidyne III is made in USA.


If any of these mics is directly connected to a flat electrical frequency response setup, the familiar bass heaviness, mid heaviness becomes apparent as happening with other mics as well.


In order to EQ for approaching flat frequency response from singer's vocal chords to listener's brain, 3 passive filters had been used between mic and preamp. All filters are connected in parallel with mic's output.


A Pleiades (130Ω,40mH) gentle slope high pass to reduce bass, mid heaviness.
A Pleiades (240Ω,11mH,68nF) to tame the reasonant HF peak of these mics at around 6KHz. A similar filter to what's inside an SM7 for making it electrically flat frequency response (presence switch).
A Western Electric transformer, 1:2 turn ratio, 1H:4H for increasing signal to noise ratio and getting rid of any very low frequency rumble by its 1H primary inductance.


Signal path:


male voice singing Feel - Robbie Williams - mic at 2-3 in - Pleiades (130Ω,40mH) - Pleiades (240Ω,11mH,68nF) - Western Electric 1:2 transformer - Sony TC-D5 Pro - Sennheiser HD580 - singer's brain


Without the 3 filters sound is tremendously bass and mid heavy even at more than 4-5 in.
Unidyne III sounds even less usable.


But when the 3 filter are connected both mics sound mich more natural without any offending bass heaviness. Midrange is very nice. The treble peak is attenuated making a full warm sound with sparkle.


The SM58 sound nice.


But the Unidyne III sounds exceptional. More detail, brighter with less sibilant problem.



The Pleiades (130Ω,40mH) is inside a Neutrik module XLR adapter. It should be fun making the same for the Pleiades (R,L,C) filter so that these filters can be connected in cascade (one after the other).