A minimal signal path shelving high frequency filter

In the referenced book Alan Parsons says he likes to boost vocals shelving at 10KHz, 14KHz etc.


It seems possible to build a passive 2 components variable shelving filter.


Just one inductor L (with taps if needed) and a variable resistor in series.


In fact this variably attenuates everything else, subtractive EQ.


Like an MD421 filter but at a high turnover frequency?


In fact one could connect 2 such filters in parallel. One for the bass reduction. The other for all reduction except the high frequencies.


So in fact 2 variable Pleiades filters, one with a very high frequency turnover implemented by a snall value of inductance, made by a few wound turns on a toroidal or ring core.


(A Pleiades filter for bass proximity compensation followed by a Pleiades filter of high frequency turnover.)


In Elvis Presley times HF might have been added not only by EQ but by the generating overtones of electron tube preamplifiers in class A.


Or additionally by the singer singing further away from the proximity compensated mic thereby further reducing bass and mid content.


Or by the fact that the singer may sing softly. When we sing softly we generate more HF and bass content (voice effort curves).


A complicated subject but a subject that can be mastered. The reader is referred to the classic Loye, Morgan paper describing flat frequency responce not from mic to speakers but from singer's vocal chords to listener's brain.


The Olson (acoustical director of RCA) paper on LF and HF EQing ribbon microphones using inductors inside the ribbon is referred too.


References:


Behind the Glass - Howard Massey


Sound pictures recording and reproducing characteristics - Loye, Morgan - JSMPE


Ribbon Velocity Microphones - Harry F. Olson - JAES