Improved Pleiades Filters

Improved Pleiades microphone filters for flat frequency response from producer's brain to listener's brain.


This update to the Pleiades wave filter is including a resistor in series with the inductor coil.


The resulting 2 terminals are then connected to pins 2 and 3 of live and return of the mic.


The inclusion of the resistor changes the low cut or high pass curve slope to a gentler one.


R can be variable for any slope.


Both passive components can fit inside a Neutrik XLR barrel adaptor.


Examples of microphones using a resistor, inductor wavefilter are the AKG D1000, Electro-Voice 642.


A typical L, R combination for close mic singing with the Sennheiser MD211 can be 85mH in series with 140Ω. A more symmetrical or balanced arrangement can be 70Ω in series with 85mH in series with 70Ω.

A 85mH, 140mH Pleiades wave filter has been tested in the following setup:


Male singing voice, usually soft to normal - MD211 at 2-4in - Pleiades wave filter (85mH,140Ω) - Sony TC-D5 Pro XLR mic in - Sennheiser HD 580


The sound is brilliant with no bass heaviness but full body.


For more detail and less hiss the Pleiades V6 booster head amp is used in the following signal path:


Male singing voice - MD211 - Pleiades (85mH,140Ω) - Pleiades V6 with Altec 4722 input trasformer - Sony TC-D5 XLR mic in - HD 580


Great natural sound.


Perhaps it may be a good idea to incorporate a variable resistor inside the an XLR barrel adaptor making the slope variable as on the brilliant Sennheiser MD421, MD441 microphones.


Can the variable resistor be an elegant rotary dial around the circumference of the barrel adaptor? Or perhaps half of the adaptor being able the rotate against the other half (with lock option) while adjusting for close to flat producer's brain to listener's brain frequency response.


References:


Electro-Voice 642 datasheet at www.outant.org


Flat frequency response from brain to brain, Sound Picture Recording and Reproducing Characteristics - D.P. Lowe and K.F. Morgan - J.S.M.P.S.E.


http://euroelectron.blogspot.gr/2018/05/a-resistor-in-series-with-inductor.html