Shure SM58 connected to Pleiades (175mH:175mH) or EMI RS106A part 2

At your risk. The Pleiades high pass filter, transformer in this case, has a slope of 6db per octave as it is 1st order (only inductance). The EMI RS106A should have a slope of 12dB per octave as it is 2nd order, C in series, L shunt, C in series, ie a T network. This explains why it sounds less dense at 150Hz cutoff setting. It sounded also very nice at 300Hz setting when mic was at 12in or 9in distance from nose. There is some buzz maybe because the filter in unbalanced or because the ground terminals at the back barrier strip are not properly set. There is no buzz or hum on the Pleiades filter as it is balanced, in fact a bifilar input transformer. A low inducatnce Pleiades filter, just an inductor of say 150mH may be tried for a less dense vocal. It may also be a good idea to create a Pleiades filter of 2nd order T network or O network for balanced. Equations for constant k filters (constant image impedance) may be used, is this what the EMI engineers or Rupert Neve did for his eqs? If memory is corrent there are also some filters called m derived. Details for all those could be found in the book Cinema Engineering, or the book Elements of sound Recording - Frayne, Wolfe. There is also a nomograph by Seito Yamasita in Radio and Television News - Aug - 1952. The equations given if R is the image impedance and fo the cutoff frequency: L=R/4PIfo (we take R, devide by 4, devide by 3.14, devide by fo), C=1/4PIfoR. where PI approximation is 3.14, Pythagoras constant. Then the T network is C/2 in series, L shunt, C/2 in series or i guess the H balanced version should have C, C on the left side, C,C on the right side. The PI version given on the article has L/2 on the left side shunt, C in series, L/2 shunt on the right side, the O balanced version i guess should be similar for inductors but 2C on top and 2C on the bottom. According to the book:Elements of Sound Recording - Frayne, Wolfe the T network should be 2C capacitor on left side, inductor L to ground, capacitor 2C on the right side. Network Pi should be on left side inductor L/2 to ground, Capacitor C on top sending music signal to the right inductor L/2 whose bottom side is connected to ground.