Capacitor shaping can work a great deal. That's all there is in the
fanciest equalizer, just multiple RC and op amps to make their effects
stronger. Simple RC using the circuit impedance for the R and adjusting
the capacitor sizes can roll up bass and treble. The series capacitor
having Xc equal to the load R sets the 3 dB corner on the LF roll off.
I'd say you want Xc to equal the load R on the microphone circuit about
500 Hz. I don't know what the microphone input resistance is so I can't
suggest a value. Backing away from the microphone will also reduce low
pitches. Adding a wind screen or two layers of wind screen will tend to
roll off some highs. Different densities of wind screen or reduced
exposure area of the microphone diaphragm will also affect the frequency
response. Making the entry into the microphone a tube instead of grill
will reduce lows (waveguide beyond cutoff attenuator), adding ribs to
the inside of the tube will roll off highs.
Then you have to add some gain to make up for the lost low tones.
You can roll off the extra highs with a shunt capacitor, with the
parallel of the source and load R's matching the Xc at the desired roll
off frequency. I'd suggest 2400 Hz as a good high end roll off
frequency, maybe 2100 Hz. I often run my passive speaker filter or my
DSP to roll off at 2100 Hz. under poor conditions or the band pass
tuning in the Corsair II works best rolling the highs off about there.
The two roll offs combined can be set independently, yet are fairly
gentle.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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