Why does the Beyer M55 microphone sound so natural?

So far it is tested mostly on male vocals at very close distance and it sounds amazing.


Why?


1. On pressure moving coil microphones the reasonant frequency is placed right at the mid band and is damped so that the microphone has flat frequency responce. Not at a low frequency as on cardioid moving coils, or ribbons. Or at high frequency as on omni condencer microphone capsules.


2. So the mic is inherently insensitive to blasts, pops and is smooth sounding at the high end too.


3. It does not seem to have the high frequency peak due to the pressure doubling effect of other omnis as it seems to be designed for flat free field (direct sound at 0 degrees) responce rather than flat diffuse field responce.


4. Diffuse field responce does not seem to matter much as the point here is getting as much clean sound electrical signal as close to the microphone. Same reasoning for outdoor or large studio recordings where the diffuse sound comes apparent at much larger distance (reverberation radius).


5 So as it behaves greatly at very small distance the signal is strong even at week voices and the signal to noise ratio is a joy to hear or rather not to hear.


6 Voltage output is large as it is 500Ω.


7 It does not need extra Pleiades filters to reduce increased bass perception due to Fletcher Munson and voice effort curves. It sings naturally with a typical inline input transformer of about 400 millHenries primary inductance.


8 Similar argument for its inherent high frequency roll off compensating for increased high frequency exaggeration due to Fletcher Munson and Voice effort curves. (These effect take place because on pop music the chosen reproduced acoustic level of voice is much louder than (reallity)). It therefore sounds flat not from microphone to loudspeaker but from vocal chords of singer to listener's brain.


9 It has due to its excellent design virualy no sibilant problems even at 0-1in from voice source.


10 It makes an extremely simple signal path. Example: Voice coil to input transformer to capacitor coupling to the grid of an electron tube preamp, such as the Pleiades V4 and it is fantastic.


There may be much more reasons, perhaps it is time to visit online the patent office and read some Beyer patents.


References:


Microphones - Bore, Peus - Neumann - free PDF
http://www.neumann.com/downloadmanager/d.php?sid=10ui5hmm8ktkfv3q1a59jhgt53&download=docu0002.PDF


Sound Picture Recording and Reproducing Characteristics - Loye, Morgan - Journal of Society of Motion Picture's Engineers - 1939 - Hollywood, California

What is inside the Neumann Dummy Head?

A very interesting paper by Stephen Peus explaining the improvements on the more recent Neumann dummy head:


Title: Natural listening with a dummy head


Translation by Stephen Temmer


Here is the link:


http://www.neumann.com/downloadmanager/d.php?sid=ivtl2hvet9fcekg29lapocmgi1&download=lect0025.PDF


Another interesting paper by Neumman is: The Dummy Head - Theory and Practice


It explains as well free field and diffuse field equalization


http://www.neumann.com/downloadmanager/d.php?sid=ivtl2hvet9fcekg29lapocmgi1&download=docu0009.PDF


And also:


 Microphones - Neumann by Bore and Peus


http://www.neumann.com/downloadmanager/d.php?sid=ivtl2hvet9fcekg29lapocmgi1&download=docu0009.PDF

Increase in very low frequency noise perception when one ear is closed

This was observed by chance.


It started off as a test on how accurately two different microphones, each one in turn, would capture outdoor ambient full spectrum noise.


Each microphone was in turn placed near an open window.


Quality was judged by listening to headphones and comparing this to how the ambient noise sounds using our own ears, head close to the window.


At one point the right hand covered the right ear. Therefore only the left ear which was close to the window would hear the ambient noise.


A dramatic increase at very low frequency rumble was perceived. It disappeared when the right ear was uncovered.


This low frequency content seems to be in the region of 10-30Hz.


The experiment was repeatedly performed with the same results. The outcome was the same in various areas including indoors. At some point an earplug was placed on one ear to exclude the possibility of hand induced vibration.


So it appears that when both ears are on there is some cancelation mechanism of this disturbing noise.


Is this another reason why a single microphone when no bass filter is added captures so unnaturally and exagerated very low frequency content?


It seems it captures what is there.


But we humans have a mechanism of canceling this disturbing sound.


A low cut to perception when we use both ears?

Understanding by feeling inductance, impedance, resistance etc

Impedance is by definition the ratio of voltage across 2 points to the current that flows through them.


Voltage and current are vectors, so impedance is too.


How come and they are vectors?


When we talk AC, ie vibrations, or oscillations, they not only have magnitude but also phase.


They are complex numbers having a real and an imaginary part.


How come?


AC means sinusoidal oscillation.


Imagine holding in our hand a LED torch.


We then make a perfect circular motion with our hand but we always point the torch perpendicularly to the wall.


We see the light projection creating a perfect sinusoidal oscillating motion on the wall.


The radius of our hand is the amplitude of this motion.


The angular velocity is analogous, proportional to frequency. This is why the angular frequency equals to 2 times PI (3.14...) times frequency. Or ω=2πf.


And the angle our hand makes at any particular moment is the phase.


So, circular motion is a very convinient way to represent vibration, oscillation.


Our hand moves on a plane.


The torch in our hand is at any particular instant at a different 2 dimension point.


The x axis is the real axis. And the y axis is the imaginary axis.


This is why we need complex numbers, ie vectors or numbers of the type (a,b), or a+jb, or e to the power of jωt where t is time or rotating vectors or phasors. They are more or less the same thing.


Impedance also exists of course on mechanical systems, acoustical systems etc.


On mechanical systems it is defined as the ratio of force to velocity.


On acoustical systems as the ratio of pressure to air velocity.


Back to electrical...


Current and voltage may be not be in phase. This happens on capacitors and inductors.


The same on mechanical systems. This happens on masses. And springs. Mass is the analogue to inductance. And springiness is analogous to capacitance. A spring is the analog of a capacitor. The capacitor tries to keep the voltage constant, the scoring tries to keep the force constant.


They obey exactly the same equations.


It is expected since they behave in exactly the same way.


By Newtons 2nd law, mass tries to keep its velocity constant and opposes changes by creating force or vice versa. (It is not easy to accelerate or stop a car).


Same with inductance it tries to keep current through it constant and opposes changes by creating voltage.


This is why an inductor in series cuts treble or high frequencies and an inductor in parallel cuts bass as on Pleiades filters. It has a lower impedance the lower the frequency is and causes a greater voltage drop at the output of a microphone. This is because a microphone has a non zero output impedance usually 200 ohms. So there is an internal voltage drop at the mic due to ohm's law.


On resistance the voltage and current are in phase.


Same on mechanical resistance or friction.


If we oscillate our palm on the beach by rubbing sand we can feel that force and velocity are in phase.


We can also feel that impedance is independent of frequency.


The same with electrical resistance of resistors on an electrical or electronic circuit.


But not so for inductance or capacitance where the reactance, (the imaginary part of impedance depends on frequency).


Why imaginary part?


Because the cause and effect are 90 degrees out of phase.


We can feel this in a very easy way on mechanical systems.


On sand as we said we feel force and velocity in phase.


But not on mass which is the equivalent of inductance.


Try for example holding in your hand something that has mass.


If we oscillate our hand at a low frequency it is easy but it gets progressively difficult the higher the frequency we want to produce.


This is a high cut filter together with the driving output impedance of ourselves.


If we try to do the same to a door which has a much higher mass we further feel this. And we have a high cut -3 dB point (amplitude drop of door oscillation) which happens now at a lower frequency.


This is inductance in series.


Or rather mass.


And we can readily feel that the sinusoidal force we apply and the sinusoidal velocity are not in phase. it may not be 90 degrees as there is friction too or resistance and we have to add vectors!


Analogous things happen with capacitors and springs, and volumes of air of bottles. And necks of bottles.


And when capacitances and inductances are connected we have electrical oscillation. Electrons move back and forth.


Same as when mass and spring are joined where we have mechanical oscillation.


Same as on a bottle. The mass of air in the neck behaves as mass or inductance trying to keep flow constant. The volume of the bottle like a spring or capacitor.


And when we carefully place our ear at the neck of the bottle we can hear the resonant frequency and if we blow we can produce a sustained oscillation.



References:


Introduction to System Dynamics - Shearer, Murphy, Richardson - MIT - Addison Wesley


Music Physics and Engineering - Olson (Staff Vice President Acoustical and Electromechnical Research, RCA)


The Feynman Lectures on Physics - Feynman, Leighton, Sands - Caltec - Addison Wesley

3 very important principles in Nature

The conservation of energy.


The conservation of momentum.


The direction of entropy which is the arrow of time.


Reference:


The Feynam Lectures in Physics - Addison Wesley


Richard Feynam Lectures on YouTube

Grundig GDM311 part 2

What a great mic !


Another specimen was tested. There seems to be great sound variation from different specimens.


As natural sound as one could expect.


Some sibilant problems when used at very close distance.


If it sounds very bad it is likely there is something wrong or the polarity needs to be reversed.


With the correct polarity it sounds very clear, surprisingly so.


If it sounds thin on the 200Ω terminal, the cause is the following:


It already has an internal autotransformer of low primary inductance, ie a Pleiades filter. The low inductance together with the output impedance of the voice coil introduce a low cut so that the mic sounds correct to listener's brain.


When it is connected to an amplifier with an input trasformer of relatively low input inductance (ie 400mH) there are then two coils (inductances) in parallel. So inductance becomes even less and the the mic departs from natural and sounds thin to listener's brain.


If it is connected to a transformer of very high input inductance such as Sowter, Jensen etc (4H to 10H) the sound is great.


Alternatively one can use the high Z out of the internal autotransformer and connect to grid of electron tube (possibly through capacitor) or gate of JFET. The sound is then fantastic. The trasformer has an unusually high turns (step up) ratio. It may need termination for damping. The Pleiades V4 used does this automatically.


The sensitivity then is so high one can hear sounds from hundred of feet away.


And the mic still sounds full and natural when one speaks or sing at 1 inch distance.


Setup, signal path:


Grunding GDM311 - Sowter 3104x - Pleiades V4 at 3.4V - Realistic disco mixer mic mino input - HD580


Or


Grundig GDM 311 H connection - Pleiades V4, 3.4Volt - Realistic disco mixer at mono mic input - Sennheiser HD580


The capsule seems to be low impedance, 10-30Ω? .


It is stepped up by an autotransformer to 200Ω or 30KΩ.


The primary inductance of the autotransformer is very low, typicaly 10mH.


This is to remove the exagerated low frequency perception to listener's brain.


If more body is needed one could experiment and wind a Pleiades trasformer using a Magnetec Nanocrystalinne Nanoperm tape wound core. One could then increase the body of sound and tailor to what is needed at any impedance.


It seems to be The mic for ASMR as it sounds fantastic at 0in and 2 can make a great binaural pair if two are placed next to one' ears while recording.

Hit Song Ingredients Part 3 Code

Code is used at any genre of music on sophisticated examples.


It is when the distance of the upper parts from the bass note departs from the obvious 1 or 3 or 5, basic major or minor triad.


An obvious example is the 80's hit song:


Maria Magdalena - Sandra (in B Dorian scale (C,F,G are sharp))
https://m.youtube.com/watch?v=epHOF91ZUFk


Even the first note sung by Sandra departs from 1, 3, 5.


When she sings "You...", the note is A. At that moment the bass is B.


So the interval by counting the notes of the B Dorian scale: B C D E F G A is 7.


Having (first thing in a song) a 7th interval may be even more rare than classical music.


The next change in bass is F sharp. At that time Samdra says the first part of "Love" using G sharp resolved to F sharp. This is an interval of 9 found in the best examples of music on our planet as on J.S. Bach's music.


The song travels us to various code non obvious intervals like 6ths etc.


And it is nice and simple with simple instrumentation and few important voices like Vivaldi.


No wander it became a great hit in Europe in the 80s.


The song may also use the hit song ingredient Varispeed to further freshen up the timbre of the voice.


Bravo, thank you Sandra and Michael Cretu.


References:


The Art of Music, or Instructions for Playing Figured Bass or Percepts and Principles - J. S. Bach


Musical Acoustics - Donald Hall


Young People's Concerts on YouTube - Leonard Bernstein