At your risk. Protect your hearing.
For many or most applications any mic may need a gentle slope low cut filter.
A directional mic will need it due to the proximity effect and also for subjective (Fletcher Munson) and voice production voice effort spectrum curve compensation [Lowe, Morgan].
A non directional mic will need the gentle slope low cut filter not for the proximity effect but for the other effects.
On previous posts it had been described that a suitable gentle slope Pleiades (R,L) filter for the Fostex M80RP, M88RP both 600Ω Japanese versions is a (40mH,130Ω)
Can a Shure VP64 omnidirectional microphone sound as good or close with a suitable choice of R L values ie Resistance in series with inductance and the total connected in parallel with the mic's output?
This test are done while singing which normal needs more low cutting than speaking especially when male voice is singing in a higher register (counterintuitively). But this is what seems to be happening in practice while singing and listening through headphones in real time.
The Fostex M80RP, is possibly 600Ω. The Shure VP64 is about 300Ω. It was stepped up by a Western Electric 1:2 transformer to 1200Ω using a previous setup used for the Shure Unidyne III, see previous experiments.
Signal path:
Male voice singing Πως θα Ηταν in F minor ie first voice note is high C - mic at 2-3 in - Pleiades (R,L) gentle slope low cut filter - WE 1:2 transformer used only for the VP64 mic - Sony TC-D5 Pro - Sennheiser HD 580 - listener's brain
As mentioned above a nice sounding Pleiades filter for the Fostex M80RP is (130Ω,40mH)
A nice filter found by experiment for the VP64 is (37,11mH)
The sound is very loud, bright, harsher than the Fostex M80RP with no bass heaviness.
Other useful combinations are (64Ω,11mH,), (29Ω,11mH), (42Ω,11mH) and (25Ω,3.8mH) which is more bright.
The (130Ω,40mH) was tried at 1200Ω, nice but perhaps harsh. 2 Pleiades filter were also tried in cascade ie (130Ω,40mH) and (240Ω,11mH) but still the low resistance 11mH filter was preferred.
Very good quality sound is possible with just one Resistor and Inductor added to a mic line.
The omnidirectional moving coil seems to sound loud and clear with some or little harshness at high frequency but cannot match the smoothness or HF detail of the coil ribbon mic. Both mics sounded great.
Latter addition: Such Pleiadss filter with low resistance and 11mH inductance sounds also very nice on the Sennheiser MD 441U3 and Fostex M55RP, see next day's post.
Reference:
Motion Picture Recording and Reproducing Characteristcs - D.P. Lowe, K.F. Morgan - Journal of the society of motion picture engineers
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