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Final Answers
© 2000-2020   Gérard P. Michon, Ph.D.

Microphones
Converting Sound Waves into Electrical Signals

 Michon
 
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Related articles on this site:

Related Links (Outside this Site)

Types of Mics and Their Uses   Alexander Briones   (Gearank, 2015-12-18).
Large and Small Diaphragm Microphones   (Neumann).
 
Microphone Geeks  (mic reviews):   Lapel | Shotgun | Studio | Live | USB
MicReviews :   Budget | Dynamic | Ribbon | Vlogging | Wireless | Boundary
Sound on Sound (SOS):  "The World's Best Recording Technology Magazine"
Matthew McGlynn :   Recording Hacks  >>  Microphone-Parts  >>  Roswell
Gearslutz :   "The #1 Website for Pro Audio."
Son et Image.  French magazine.   |   Stereophile.  Listening.
 
Microphone Makers  (in random order)   Sennheiser  |  RØDE  |  AKG  |  Shure  |  Audio-Technica  |  Earthworks  |  Electro Voice  |  Heil Sound  |  Lewitt  |  AEA  |  Audix  |  Blue  |  Behringer  |  MXL  |  Sony  |  Telefunken  |  ShuaiYin  |  Azden  |  Samson  |  Schoeps  |  Golden Age Project  |  Coles Electroacoustics  |  Sterling  |  Aston  |  Beyerdynamic  |  Warm Audio  |  Sanken  |  ...
 
Modifiers :   Michael Joly   |   John Bonnell   |   MicParts   |   Mic & Mod
 
Retailers :   B&H  |  Amazon  |  Sweetwater  |  Thomann  |  Guitar Center  |  Reverb  |  Sam Ash  |  zZounds  |  Full Compass  |  American Musical  |  Front End Audio  |  Gauge

Videos : 
Get Good Sound with a DSLR  (40:36)  by  Alex  (RØDE, 2013-03-05).
Microphone electronics  (9:03)  by  Project studio handbook  (2016-01-28).
Recording Vocals Masterclass  (24:08)  by  Marcel van Limbeek  (2015-04-26).

 
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Microphones in Focus

This is about the microphones themselves.  For their use in recording,  see Audio. In comparative tables,  model numbers in  italics  indicate specialized microphones  (e.g., percussions).


(2017-05-25)   Sound in air
Reversible local oscillations.

 Come back later, we're
 still working on this one...

Tin-can telephone  (Lover's telephone)  by  Robert Hooke (1664).
Numericana :   The physics of sound
 
Recording Audio for Digital Video (21:04)  by  John P. Hess  (Filmmaker IQ,  2014-09-15).
Microphone electronicss (9:03)  by  Project studio handbook  (2016-01-28).


(2014-06-05)   Classification of Microphones
Exploiting the variation with pressure of another physica; variable.

Historically,  the problem of converting sound into an electrical signal was first solved by devising a resistor sensitive to sound  (this dominated the telephone industry for 60 years).  Now,  most microphones are based on the variation with sound pressure of either an inductance or a capacitance.

Alternative possibilities include  piezoelectric  microphones,  which rely on the voltages generated by varying pressure in certain solids.

Unlike all of the above,  optical microphones can measure the variation of air pressure directly, without the help of any kind of moving membrane,  but they're not yet commonplace.

Here's a complete classification of the different types of microphones:

Transforming one physical quantity into another is called  transducing.  Ultimately, all microphones are transducers of sound waves into electrical signals  (mostly, variations in voltage).

To do this,  various intermediary techniques can be employed.  In some condenser microphones, for example, the sound-sensitive capacity of the capsule is part of a low-noise radio-frequency (RF) circuit.  That way,  sound modulates the frequency of the primary circuit, which is then demodulated to retrieve the signal.  I'm told that Sennheiser's MKH series works this way,  including the legendary MKH 416.  (That's called  RF biasing.)

Loudspeaker History  by  by  Steven E. Schoenherr  (UCSD, 2001).
Edward Christopher "E.C." Wente (1889-1972)   |   Albert L. Thuras (1889-1945)


(2014-06-05)   Unified Description of the Two Main Microphone Types
Condenser  (varying capacitor)  and  dynamic  (varying inductor).

Here, we'll focus only on capacitive and inductive microphones  (condenser microphones and dynamic microphones)  which are currently the most commonly used in audio applications.  They are electrical duals of each other and it's enlightening to discuss them in parallel...

An  ideal  capacitor  (resp. inductor)  is a two-lead component characterized by two parameters,  an electrical one and a geometrical one:  voltage  U  and capacitance  C  (resp. current  I  and  inductance  L)  whose product is equal to an extensive electromagnetic quantity  stored  by rhe device:  the electric charge  q  (resp. the magnetic flux F).  In the absence of external electromagnetic fields,  we have:

q   =   C U               F   =   L I

Differentiating this with respect to time,  we obtain:

I   =   C' U  +  C U'               U   =   L' I  +  L I'

As mechanically-induced motion causes  C  (resp.  L)  to vary,  a signal is generated which is proportional to the mechanical speeds involved.  If the geometry is tied to the position of a mechanical membrane, that dynamical position is easily retrieved by integration...

The above analysis is fairly realistic for capacitive (condenser) microphones but is utterly inadequate for inductive microphones which rely heavily on strong magnetic fields  (which dwarf the magnetic field induced by the circuit itself).  If we make the assumption  (which is a valid one for ribbon microphones)  that the only part of the circuit which can move does so in a plane orthogonal to a constant magnetic field and call S the apparent area of the circuit "seen" by that field,  then the following expression for the flux enclosed by the circuit holds:

F   =   F0  +  L I  +  B S

The first of those three terms is an irrelevant constant and the second term is dwarved by the third.  Therefore,  in the main:

U   =   F'   =   B S'

Between two strong neodymium magnets  (e.g., BX044-N52)  the magnetic field  B  can be about  1 T.

Longitudinally,  a corrugated aluminum strip behaves essentially like a ribbon with a very low Young modulus  YC  (this depends on the thickness of the material and the shape of the corrugation but, paradoxically, not on its scale).  Transversally,  it's virtually impossible for the ribbon to bend.  So,  a corrugated ribbon behaves like a membrane whose  mean curvature  H  is  half  the  longitudinal curvature  of the ribbon  (as the transversal curvature is utterly negligible).  The pressure difference between the two sides of the membrane is given by the  Young-Laplace equation:

p -  p-   =   2 g H   =   g / r.

 Come back later, we're
 still working on this one...

"Microphones 101"  by  Doug Ford,  former head-designer at  Røde,  with  Dave Jones   (April-June 2014):
Intro | Pickup patterns | Condenser & electret | Condenser design | Electret design | Phantom | Preamp
 
Numericana :   Microphone reviews


(2018-01-14)   Noise Floor   (Hiss)
Signal to Noise Ratio   (S/N or SNR).

 Come back later, we're
 still working on this one...

Signal-to-noise ratio   |   Noise figure   |   Shannon-Hartley theorem
Dolby noise reduction for magnetic tapes   |   Dolby Laboratories   |   Ray Dolby (1933-2013)


(2018-01-25)   Rating the Sensitivities of Microphones
Sensitivity is the ratio of voltage  output  to sound pressure  input.

The  sensitivity  of a microphone is defined as the ratio of the  variation  in its  electromotive force  output  (i.e., the open-circuit voltage it produces)  to the corresponding  variation  in sound pressure input.  When neither is too large, that's a constant.

In engineering terms,  it's useful to think of it as the ratio of two  time-derivatives.  That much is clear at the outset when  designing a microphone.  Voltage is unrelated to static pressure.

That  sensitivity  is most commonly expressed in  mV/Pa  (millivolt per pascal)  assuming a standard sinusoidal sound signal of 1 Pascal amplitude  (94 dB SPL)  at  1 kHz.

When  decibels  are used,  the  dBV/Pa  scale is  usually  understood.  Thus,  the stated  dB  sensitivity rating is  20  times the  decimal logarithm  of the sensitivity expressed in V/Pa  (which is the standard SI unit for sensitivity).

For example,  Audio-Technica  presents the high sensitivity of their  BP4071  shotgun microphone  by giving two equivalent figures:

Sensitivity of   35.5 mV/Pa   is  -29 dB    (re:  1 V  at  1 Pa).

Indeed,  we have:   20 log (0.0355 V/Pa)   =   -28.99543... dBV/Pa

A microphone is said to be  loud  when its sensitivity is high  (the opposite of  loud  is  soft).  Normally, the louder the better, because of a lesser need for amplification  (as a signal is amplified,  so is the accompanying noise).  However, there's such a thing as too much of a good thing:  If a microphone is too loud,  it may generate unexpectedly high voltages at the input of the next circuits  (preamplifiers).  That won't damage them but they'll  saturate  or  clip  (same thing)  which will introduce unacceptable distortion.

Today,  microphones are rarely designed with a sensitivity exceeding  50 mV/Pa  (that's  -26 dBV/Pa).  The discontinued predecessor of the aforementioned  BP4071  was the  AT4071a  which had a nominal sensitivity of  89.1 mV/Pa  (that was -21 dB).  This is considered  way  too loud by today's standards for general-purpose use  (although bird lovers still like this kind of sensitivity in a directional microphone).

The sensitivity rating of a microphone is always stated for  on-axis  sound  (coming from the preferred direction of the microphone, which gives the maximum sensitivity).  Polar patterns  are charts giving relative sensitivity as a function of direction by reference to that basic sensitivity  (de facto,  the  0 dB  level for a particular microphone).

Warning :   An older decibel scale for microphone sensitivity is still floating around which differs from the modern one by  20 db.  In that obsolete scale,  the aforementioned  BP4071  would have been quoted as having a sensitivity of  -49 dB  (which could be misinterpreted as quite low).

The discrepancy comes from the former use in acoustics of the units of pressure still preferred by many meteorologists.  When meteorologists in France and elsewhere were criticized for issuing TV reports expressed  in  millibars  (1 mb = 100 Pa)  instead of a proper  SI unit,  they didn't change their numbers but started using the  SI-equivalent  hectopascal  (which is correct albeit arguably  somewhat weird).

In the old days,  audio engineers were routinely using the  microbar  (0.1 Pa)  as their unit of pressure  (this was an alternate name for the official unit of pressure in the CGS system,  namely the  dyne per square centimeter).  This made the  volt per microbar  (10 V/Pa)  their unit for microphone sensitivity.  Using that unit,  the numerical values of sensitivities are ten times smaller than the values in  V/Pa.  Expressed in decibels,  they're thus  20 dB  lower,  as advertised!

In  Numericana,  microphone sensitivities are only given in  mV/Pa.  Not only does this avoid the aforementioned ambiguity of decibels,  but it also serves as a constant reminder of what sensitivity is all about.

Unit conversions is a known source of distress.  NASA  once crashed a spacecraft on Mars because of that.  As I was looking for data relevant to this page,  I came across a  discussion between audio afficionados  where the above  20 dB  offset is mistaken for real substance.

Electromotive force vs. measured voltage :

Microphone sensitivities are best expressed in terms of  open-circuit voltages  (the common name given to  electromotive forces).  So defined,  sensitivity  depends only on the microphone itself,  not on whatever load it may have to drive  (usually, the input impedance  R  of some preamplifier).

Nevertheless,  some manufacturers give the actual voltage  V  that would be observed per unit of sound pressure into a load of specified impedance within the range they recommend  (e.g.,  A = 1 kW).  That number is slightly smaller than the aforementioned intrinsic sensitivity  U.  The relation between the two is obtained by observing that the microphone's output current is equal to the preamplifier's input current.  Let  z  be the microphone's output impedance and  Z  be the preamp's input impedance:

 Microphone and Preamplifier
  i   =   U / (Z+z)   =   V / Z
(at 1 Pa).   Therefore:
 
U   =   ( 1 + z/Z ) V

For example, if a  200 W  microphone is said to yield  10 mV/Pa  into a  1 kW  load,  then we just quote its  intrinsic sensitivity  U  as  12 mV/Pa.

Such a microphone would drive a  2.5 kW  load with

12 / (1 + 200 /2500)   =   11.111 mV/Pa.

At a given audio frequency,  the electromotive force  and  the output impedance of a microphone can be deduced from electrical measurements  (current, voltage and phase difference between the two)  under just two different load.  There's no need for acoustic calibration  (we do need such a calibration to establish the sensitivity though).

The electric noise of a  dynamic  microphone depends entirely on the how its impedance as a function of frequency  (to that should be added the acoustic thermal noise at a prescribed tem[erature and pressure,  which depends mostly on the size of the diaphragm).


(2018-02-05)   Microphone directionality.  Polar pickup patterns.
Omnidirectional, bidirectional, cardioid, etc.

 Come back later, we're
 still working on this one...


(2018-02-05)  Dual-Diaphragm Microphones for variable pickup patterns.
A cardioid is the  sum  of omnidirectional and bidirectional patterns.

 Come back later, we're
 still working on this one...

Multi-pattern and variable pickup pattern:

Mixing equal parts of an omnidirectional pickup pattern and a bidirectional one  (figure-8)  yields a cardioid pattern.  Other proportions in this type of mixing also yields the other  traditional  microphone pickup patterns:

  • Subcardioid  pattern  (between omnidirectional and cardioid).
  • Supercardioid  pattern  (between cardioid and figure-of-eight).

The above five patterns and the four intermediate ones between them yield a palette of nine patterns,  which are commonly available at the flip of a switch in  some  multi-pattern  microphones.  The term  hypercardioid  is sometimes applied to any such mix but it's most often reserved to patterns with a wide  cone of silence  up to  (but excluding)  the bidirectional figure-of-eight itself  (90° angle of silence).

Variable-pattern  microphones  (e.g., CAD Audio M179)  even allow you the freedom to dial anything in-between.

Note that a two-diaphragm microphone which is capable of recording at least two pickup patterns from the above standard family can also be used to reconstruct  any  of them in post-production.  For example, if the omnidirectional signal is on the left channel and the figure-8 bidirectional signal is on the right channel,  Then, you obtain a forward cardioid by adding the two channels and a backward cardioid by subtracting them  (opamps were originally intended do perform exactly this sort of operations).  This way, you can choose the pickup pattern  after  recording.

Any dual-diaphragm microphone could be modified into a pseudo-stereo microphone capable of recording the two separate phase-tracks just described.  Two products offer this capability straight out-of-the-box:

  • The  Lewitt LCT 640 TS  microphone  (TS stands for  twin system)  whose secondary output is on a mini-XLR connector  (sideways).
  • The  MS ("Mid Side")  attachment for the 10-pin connector of Zoom recorders  (H5, H6, F1, F4, F8)  records separately the signals from two capsules:  Forward  cardioid and  sideways  bidirectional.

Other multiple-diaphragm configurations would provide other capabilities.

Multi-pattern dual-diaphragm microphones  (data is for cardioid pattern)
MakeModelPrice mV/PaHiss Max.BandwidthW
TelefunkenU87 $8999 24.59 dB127 dB20Hz-20kHz400
sE ElectronicsRNT $3249 1618 dB151 dB18Hz-20kHz30
NeumannU87 Ai $3200 33.612 dB117 dB20Hz-20kHz200
BlueKiwi $1999 198.5 dB138 dB20Hz-20kHz50
SonyC38-B $1880 424 dB140 dB30Hz-18kHz250
AKGC414 xls$1074 236 dB140 dB20Hz-20kHz200
RoswellDelphos $8994012 dB 20Hz-16kHz200
Lewitt  LCT 640 TS $89931.410.5 dB134 dB20Hz-20kHz110
ShureKSM 44A $999 29.84 dB134 dB20Hz-20kHz50
ShureKSM 44 $99929.87 dB132 dB20Hz-20kHz150
AKGC314 $699 208 dB 20Hz-20kHz200
Audio-TechnicaAT4050 $699 15.817 dB149 dB20Hz-18kHz100
Røde [tube]K2 $699 1610 dB162 dB20Hz-20kHz200
Warm AudioWA-87 $599 ?17 dB?125 dB20Hz-20kHz150
sE ElectronicsT2 $499 25.116 dB122 dB20Hz-20kHz50
AstonSpirit $449 2614 dB138 dB20Hz-20kHz
RødeNT2-A $399 167 dB147 dB20Hz-20kHz200
Audio-TechnicaAT2050 $229 7.917 dB149 dB20Hz-20kHz120
CAD AudioM179 $199 1611 dB123 dB10Hz-20kHz200
SenalSCM 660 $175 22.418 dB130 dB20Hz-20kHz100
CADGXL3000 $159 1320 dB125 dB35Hz-20kHz200
BehringerC-3 $70 1023 dB142 dB40Hz-18kHz350

Multi-pattern microphones  by  Davida Rochman   (Shure Blog,  2014-08-11).
 
Choosing a mic for vocalist Sammi O'Rourke (5:36)  by  Jason de Wilde   (AIM Sidney,  2015-07-30).
KSM 44, New Dual-Diaphragm Condenser, in 2008 (3:21)  by  Tim Vear   (the improved KSM 44A appeared in 2010).
Lewitt LCT 640 TS:  A true next-gen microphone (5:36)  by  Lewitt   (2016-09-19).


(2018-05-08)   Multiple-capsule microphones
Putting several very different microphone capsules in the sams housing.

Driven by professional demand,  some manufacturers have put several capsules using different technologies behind the same grille  (e.g., a condenser mic and a dynamic mic next to each other).  This allows an adjustable frequency response but there are complicated phase issues at high-frequency, which restrict such compound microphones to specialized applications  (e.g., kick drum).

Compound microphones  (including more than one capsule)
MakeModelPrice mV/PaHiss Max.BandwidthW
Lewitt  DTP 640 REX $3490.4
2.4
28 dB150 dB20Hz-16kHz
20Hz-20kHz
500
200


(2018-01-29)   Accurately Measuring Sound
Calibrated  ¼''  or  ½''  omnidirectional  measurement microphones.

Most prosumer  measuring microphones  have a  ¼''  capsule  (6 mm diaphragm).  Professionals sometimes use smaller membranes  (3 mm)  which are more accurate in the upper-part of the audio spectrum.  They tend to prefer expensive low-noise  ½''  units for general use.

Acoustic Calibrators  (1 kHz,  94 dB SPL) :

By convention,  absolute calibration  of a sound-measuring instrument is always done at  1000 Hz.  For that purpose,  standard sound sources  are available which deliver precisely  94 dB SPL  into a  force-fit  microphone port allowing cylindrical microphone heads up to  1''  in diameter  (sometimes only ½'').  Smaller microphones require adapters which may or may not be included with calibrating units.  Below is a list of current models of such  acoustical calibrators.  All of these can work either at  94 db  or  114 dB  (the latter setting is helpful in a noisy environment).

  • Brüel & Kjær 4231.  0.2 dB accuracy.  $1000 used!
  • General Radio 1562-A.  0.172 dB accuracy.  $2694 new.
  • Cirrus CR 515.  0.2 dB accuracy.  ½" port.
  • Brüel & Kjær 4230.  Discontinued.
  • Landtek ND9.  0.3 dB accuracy.  $129.   [ Fail ]
  • Cirrus CR 514  0.4 dB accuracy.  ½" port.
  • Reed R8090.  0.5 dB accuracy.  ½" diameter.  $175.
  • Ruby Electronics SC-05.  0.5 dB accuracy.  $180.
  • Amprobe SM-CAL1.  0.5 dB accuracy.  $187.
  • Sper scientific 850016.  0.5 dB accuracy.  $256.   [ Video ]
  • Fluke SM-CAL1.  0.5 dB accuracy.  $270.
  • Extech 407766.  0.5 dB accuracy.  $313.

Now, the calibrators themselves drift out of calibration and have to be recalibrated yearly by the manufacturer.  Most people will only trust  Brüel & Kjær  (or possibly Cirrus)  for that follow-up.

Sound Meters,  Measurement Microphones :

Measurement microphones  are designed to be as linear as possible,  They have a flat frequency response throughout the audio range and deviations must be carefully documented  (see example below).  Tiny diaphragms help keep resonant frequencies safely outside of the audio domain.

Many uncalibrated consumer models are just intended for the analysis of  room acoustics  and cannot be trusted beyond a precision of  2 dB  or  3 dB.  The following models are thus  not recommended  for scientific applications:

A much better precision is offered at a similar cost with any of the models listed  below.  Each such unit comes with an individual calibration curve made with a professional instrument.  The resulting on-axis  frequency response  is typically made available online  (tied to the serial number of every microphone)  in a digital form suitable for audio-analysis software.  Sonarworks  also provides an off-axis curve.

Some measurement microphones which come with individual calibration curves :
MakeModelPrice mV/PaHiss Max.BandwidthW
Dayton AudioEMM-6 $50 1224 dB127 dB18Hz-20kHz200
MiniDSPUMIK-1 $75USB20 dB133 dB20Hz-20kHzusb
SonarworksXREF 20 $851426 dB132 dB20Hz-20kHz 
BeyerdynamicMM-1 $2001537 dB122 dB20Hz-20kHz160
AudixTM1-Plus $400 7.228 dB130 dB20Hz-25kHz200
EarthworksM23 $5003420 dB138 dB9Hz-23kHz65
EarthworksM30 $7003420 dB138 dB5Hz-30kHz65

Earthworks  also sells the  M30  in matched sets  (for about $1500 a pair)  for  stereo  recording.  They're the industry standard for true-to-life response.

All  measurement microphones could be used for recording,  but their tiny diaphragms  (usually  6 mm)  makes them about as noisy as  lavalier mics.

Dayton Audio's  Electret Measurement Microphone  EMM6

With a street price of $50  (I just got mine on sale for $40)  the EMM6 is the most affordable of the above.  Packed with each unit is a dated plot of its frequency response.  The corresponding data is also available online  (tied to the serial number)  in the form of a tab-separated text file  (ready to import into Excel or other specialized software).  That file contains measurements at a precision of  0.1 dB  for  256  frequencies whose logarithms are evenly spaced,  from  20 Hz  (n = 0)  to  20000 Hz  (n = 255).  That's to say:

fn   =   (20 Hz) 10 n/85     (for  n between 0 and 255 = 3 x 85)

The values are given in decibels relative to the level at frequency  f145 = 1016.0436 Hz  which is given tersely in absolute terms  (in dBV/Pa)  on the first line of the data which reads,  in the example of my own unit:

*1000Hz	-39.6

This misleading header actually indicates that the sensitivity of this particular microphone is  -39.6 dBV/Pa  (i.e., about 10.47 mV/Pa)  at precisely  1016.04 Hz  (not 1000 Hz).

 Blowup   The blow-up at right shows the frequency-response near 1 kHz of my own EMM6.  Each black square is precisely a single data-point  (it covers exactly one pixel in the full graph shown below,  where the height of each pixel is just  0.1 dBV/Pa.)
 Dayton Audio EMM6 Electret Measurement Microphone

To obtain a very precise value of the sensitivity at exactly  1 kHz  (which is the usual standard)  we remark that 1000 Hz = fn  when

n   =   85 log 50   =   144.4124503685615984...   =   145 - 0.58754963...

The  data for my own unit  says that the sensitivity for  f144  is 0.2 dB  above the level for the aforementioned  ad hoc  reference frequency  (f145 ).  Thus,  the response at  1000 Hz  is best obtained by linear interpolation:

-39.6  +  0.2 (0.58754963...)   =   -39.5 dBV/Pa   (or about  10.6 mV/Pa)

Now, all of the above are based on actual voltage measurements performed by Dayton into a  load  of  1000 W  (precisely so, hopefully).  As the nominal impedance of the EMM6 is  200 W,  its  intrinsic sensitivity  is obtained after a  correction  of  20%  (i.e., 1.58 dB).  Before rounding,  we obtain:

-37.899... dB/Pa   or   12.7367 mV/Pa

Brüel & KjærMeasuring microphones  (August 1994).
 
NTI Measurement Microphones Overview   |   NTI Web Shop
Measurement microphones in the  Thomann Catalog  (Germany).
11 measuring microphones compared  by  Ethan Winer   (RealTraps, 2013-08-11).
 
Dayton Audio's  EMM6, UMM6 and OmniMic V2 (2:48)  Parts Express  (2016-07-01).


(2018-02-09)   Input Attenuator   (Pad)
A switchable input pad allows a microphone to record louder sounds.

Such a pad is a network of resistors placed just after the microphone capsule to prevent the subsequent active electronics from saturating  ("clipping").

All About Pads  by  Rick Chinn  (2001, 2014-02-19).


(2018-02-09)   Low Cut Filter   =   High Pass Filter  (HPF)
Filtering out the lowest audio frequencies.

On many microphones,  a switchable  low cut  filter is provided to get rid of the low-audio and sub-audio hum and rumble.  Typically,  a corner frequency of  80 Hz  is used.

Most manufacturers are content with a simple  first-order filter (6 dB/octave)  which provides a modest  12 dB  attenuation at  20 Hz.

Others, like  Audio-Technica  will do more and they should be commended for it.  If you need low-cut in an urban environment,  the more attenuation the better.  Even in their entry-level  AT2035,  the low-cut filter they provide is  second-order (12 dB/octave)  for a  24 dB  attenuation at  20 Hz.

On  Audio-Technica  shotgun microphones  (AT897, BP4073, BP4071)  the switchable low-cut filter is third-order  (18 dB per octave)  and provides an attenuation of  36 dB at  20 Hz  (that's 12 dB at 50 Hz).

Low-cut filter  vs.  low-frequency shelf (2:48)  Parts Express  (2016-07-01).


(2017-11-22)   Characteristics of Full-Size Wired Microphones
Condenser type  (varying capacitor)  or  dynamic type  (varying inductor).

Microphones currently being produced range in price from  $1.67  to  thousands of dollars  (the  AKG C12 VR  sells for &5999).  Used vintage  Neuman U67  tube LDC  microphones are typically sold for $9000-$16000, depending on condition.  At least part of that madness is due to a nostalgia for the particular type of  distortion  introduced by  tube  (or  valve)  circuits.

For some obscure reason,  tube amplifiers tend to distort a waveform symmetrically,  which is another way to say that they introduce more  even  harmonics  than odd ones.  The type of sound so produced is normally associated with female voices  (it would seem that  Adam's apple  on a male  voice box  is responsible for producing asymmetrical waveforms rich in odd harmonics).  Whatever the exact reason may be,  this is just one example of an acquired taste among audiophiles which has little or nothing to do with high-fidelity.  If anything,  modern semiconductor circuits have better fidelity qualities,  quantitatively speaking.  The good news is that those high-price instruments are not a necessary part of high-fidelity home recording.

Designing microphones  is an  art form  in itself.  Microphones are a crucial tool for musicians and an object of worship for countless  audiophiles.  Just enumerating the main aspects on which that subculture is based will serve to demonstrate that we can only scratch the surface here  (focusing, as usual, on nontrivial numerical aspects besides cost).  All these aspects are interrelated:

  • Price, cost of ownership.
  • Options and customizability.
  • Look, feel and durability.
  • Size and weight.
  • Possible mounts  (handheld, tabletop, lapel, stand, arm, boom).
  • Sensitivity at various frequencies  (bandwidth  &  microstructure).
  • Impedance magnitude and phase shift  (as functions of frequency).
  • Directivity  (polar pattern)  at various frequencies.
  • Proximity effect at various frequencies.
  • Noise figure,  noise floor  (hiss).

The previously introduced concept of  sensitivity  influences greatly overall noise performance because lower sensitivity demands greater subsequent amplification,  which magnifies hiss just as much as the useful signal.

The  self-noise  (or  equivalent noise level,  henceforth tabulated as  hiss)  of a microphone is the loudness of the signal it produces by itself in an isolated soundproof enclosure  (it would be cheating to report only the electric noise of the apparatus without the microphone capsule).  The same figure of merit is sometimes reported as a  signal-to-noise ratio  (SNR)  assuming a  1 kHz  sinusoidal  standard soundwave  of  1 Pa  amplitude  (94 dB SPL):

SNR   =   94 dB  -  (self-noise, dB)

The  dynamic range  of a microphone is defined as the  decibel  difference between the aforementioned self-noise and the top loudness it can record,  with less than  1%  THD  (total harmonic distortion).

The  nominal output impedance  is expressed in ohms  (W).  A microphone is normally plugged into a  preamplifier  whose input impedance shouldn't be lower than whatever is specified by the microphone manufacturer  On the other hand,  it shouldn't be too high either because high impedance breeds noise.  A time-honored  rule of thumb  is to load a microphone with five to ten times its own output impedance.

Some compact microphones sold with on-camera mounts :
MakeModelPrice mV/PaHiss Max.BandwidthW
MovoVXR10 $40 4018 dB 35Hz-18kHz200

Download Official Microphone Drivers
 
How to get professional DSLR audio: The RØDE VideoMic Guide  (16:57)  by  Alex  (2014-11-25).
Audio Filmmaking Basics (18:08)   Basic Filmmaker  (2015-08-20).
Best Microphones for Video (0-$500)  by  Tony Northrup  (2016-08-30).
This Light and Mic Stand Changes Everything  by  Caleb Pike  (2017-11-02).
Every Rode Shotgun Video Mic Compared! $59 - $299  (23:46)  by  Max Yuryev  (2017-11-24).
Great $40 Camera Microphone  Movo VXR10 Review  (7:52)  by  Caleb Pike  (2017-12-05).
$25 vs. $299 - Takstar beats the Rode VideoMic Pro?  (11:52)  by  Max Yuryev  (2017-10-13).
 
Numericana :   Decibels (db) & Sound levels   |   Microphone design


(2018-02-01)   Acoustical Properties of Large Circular Diaphragms
Resonant frequencies and frequency-dependence of pickup patterns.

 Neumann U87  The  diaphragm  of a condenser microphone consists of a thin circular membrane whose rim is attached under tension to a rigid hollow cylinder.  In the so-called  center terminated  variant,  the diaphragm is also anchored by a small screw at the center,  where it can neither move nor tilt...
That method is used, in particular, in good  ½''  measurement microphones.  It presents three major advantages:

  • The center point can be used for electrical contact.
  • Resonances are suppressed if the center isn't a  node.
  • Resonances are suppressed if the gradient at the center is nonzero.

Those last two properties eliminate the lowest resonant frequencies for a circular membrane  of prescribed size,  areal weight and tension.  That helps remove all resonant frequencies away from the audio range.  However, the central contact restricts the amplitude of the diaphragm's motion at lower frequencies and thus reduces the basic  sensitivity  of the microphone.

condenser microphone  is formed by the varying capacitor consisting of one such diaphragm opposite a rigid  backplate  (polarized by an external voltage and/or an electret).  When those two form a closed  capsule,  an  omnidirectional  pickup pattern is obtained  (at least at low frequencies). 

A microphone capsule is never completely closed,  or else it could bend  (or even pop)  in response to slow changes in atmospheric pressure.  There are just tiny vents which allow air to go in and out of the capsule fairly slowly,  with little or no impact at audio frequencies.  The best designs will make the vents just large enough to cancel hum just below the audio range  (which is usually assumed to start at  20 Hz,  although that's definitely not audible).
 Standing Wave in a Circular Membrane

The mathematical simplicity of the above configurations makes a complete theoretical analysis possible,  which may serve as a useful basis for experimental refinements in the actual design of commercial microphones.

Another aspect amenable to pencil-and-paper analysis  (barely so)  is the pickup pattern  (sensitivity as a function of direction)  of a large-diaphragm for a sound having a wavelength commensurate with its size  (for much larger wavelengths,  the pickup pattern is omnidirectional).

Vibrations of a circular membrane


(2018-01-22)   Large-Diaphragm Condenser Microphones   (LDC)
Quintessential capacitive microphones.  Every voiceover artist has one.

Most condenser microphones use the  48 V  phantom power normally found on  XLR  sockets  (one more reason to get an  XLR1  audio adapter,  if you shoot video with a Panasonic  Lumix GH5).

What's the fuss about large diaphragms?   Well,  the larger the diaphragm the quieter the microphone,  but too large a diaphragm will struggle with the upper part of the audio spectrum,  especially off-axis,  as different parts of the membrane see different phases of the soundwave  (at  20 kHz  the wavelength is only  17 mm).
 
Earthworks  achieved the extreme bandwidth  (30-33kHz)  of their  SV33  flagship by limiting the diameter of the diaphragm to  14 mm.  The price they paid was a  15 dB  noise-floor  which is unimpressive for a microphone at that price-point  ($2499).  The membranes of more typical LDC microphones are about  1''  in diameter  (25.4 mm).

One popular LDC microphone is the affordable  AT2020  from  Audio-Technica  ($99 bundle).  I went instead for its big brother,  the  AT2035  ($149 bundle)  because of a side-by-side sound comparison on  YouTube.

Also,  unlike the  AT2020,  the  AT2035  has two desirable features:

  • Switchable  10 dB  in-line attenuator  ("pad")  whose effect is equivalent to tripling the distance from the sound source.
  • Switchable  second-order high-pass filter  with  80 Hz  corner frequency,  which helps cut out hum and rumble in an  urban environment.  (Other makes often provide only first-order.)

The  AT2035  gets  rave reviews  as the best in its class  (I wouldn't consider a higher class for home use,  following the  law of diminishing returns).  That microphone comes with a soft pouch and a shockmount  (including a plastic thread adapter; 5/8''-27 male to 3/8''-16 female).  I got mine with a complimentary 10-ft XLR cable and Neewer® pop screen.  All for $149.  The shockmount by itself  (AT8458)  would sell for  $79.  (Third-party shockmounts go for  $10,  a short cable is about $9 and the pop shield is $7.)

 AT2035 frequency response

The  AT2035  was released in 2008.  It's built around a  center-terminated  24.3 mm  diaphragm  (0.96").  It uses  back electret  polarization,  which helps accommodate a wide range of phantom voltages  (from 11V to 52V).  Some purists still scoff at this approach,  compared to what they call  true  condenser microphones,  in spite of the fact that the electret technology has been around for more than 50 years and helps deliver  superb  performance.

To address such queasies within the  Audio-Technica  ladder,  the  AT2035  is bracketed by two condenser microphones which are purely DC-biased without electrets,  the AT2020 and the AT4040  (which both demand 48V phantom power).  The latter costs twice as much as the  AT2035  without offering any improvement in self-noise.  (Since it's  1 dB  more sensitive,  it's technically just  1 dB  quieter.) 

This isn't the whole story, though:  The noise figure of the AT4040 was achieved in spite of the fact that it uses only a  smaller diaphragm of  20.4 mm  (0.8'')  which helps with transient response.
 
Although my own ears couldn't detect those subtleties  (I'm now on the wrong side of sixty)  I could easily see that the AT4040 grille is more transparent,  which can be acoustically desirable.
 
Røde's  NT1-A  still looks like a better upgrade,  as a true condenser microphone which is  8 dB  quieter than the  AT2035  (for only  $80  more).  For another $40,  I find their  NT1  even more tempting with its true-to-life flat-response sound and praised shockmount  (Rycote lyre).

Audio-Technica  reports  that they incorporated into the  AT2035  the honeycomb diaphragm design used in their own  $3000  AT5040  flagship,  for increased surface area and enhanced performance.

In the following table,  we give a wide selection of the medium-to-large condenser microphones available today.  All of those are single-diaphragm microphones  (we list separately  dual diaphragm microphones  featuring selectable pickup patterns).  They're all cardioid microphones,  except :

  • Earthworks SR40V  (hypercardioid).
  • CAD Audio E100s,  (supercardioid).

Some current LDC microphones   (Data with all pads and filters disengaged.)
MakeModelPrice mV/PaHiss Max.BandwidthW
Audio-TechnicaAT5040 $299956.25 dB142 dB20Hz-20kHz50
EarthworksSV33 $24991015 dB145 dB30Hz-33kHz65
NeumannTLM 49 $17001412 dB129 dB20Hz-20kHz50
VioletGlobe $138623.16.5 dB134 dB20Hz-20kHz50
NeumannTLM 103 $1300 247 dB138 dB20Hz-20kHz50
BlueMouse $1250 218 dB138 dB20Hz-20kHz150
RoswellRA-VO $9991010 dB50Hz-15kHz112
EarthworksSR40V $9992020 dB145 dB50Hz-40kHz65
ShureKSM42 $79914.18.5 dB131 dB60Hz-20kHz147
NeumannTLM 102 $699 1112 dB144 dB20Hz-20kHz50
LewittLCT 550 $699363 dB143 dB20Hz-20kHz150
ShureKSM32 $549 1613 dB139 dB20Hz-20kHz150
CAD AudioE100s $499 283.7 dB140 dB20Hz-20kHz150
sE ElectronicssE2200 $429 23.712 dB113 dB20Hz-20kHz50
Audio TechnicaAT4033a $399 25.117 dB145 dB30Hz-20kHz100
Blue Baby Bottle SL $39939.810.8 dB134 dB20Hz-20kHz50
AKGC214 $3992013 dB136 dB20Hz-20kHz200
GaugeECM-87 $32912.517 dB128 dB20Hz-20kHz200
RødeNT1000 $329 15.86 dB140 dB20Hz-20kHz100
SennheiserMK 4 $3002510 dB140 dB20Hz-20kHz50
Roswell  Mini K47 $2991813 dB20Hz-16kHz114
BlueBluebird $29928.511.8 dB138 dB20Hz-20kHz50
Audio-TechnicaAT4040 $29925.112 dB145 dB20Hz-20kHz100
ShureSM 27 $299 14.19.5 dB138 dB20Hz-20kHz150
AstonOrigin $269 23.718 dB127 dB20Hz-20kHz
LewittLCT 440 $26927.47 dB140 dB20Hz-20kHz110
RødeNT1 $269 354.5 dB132 dB20Hz-20kHz100
OktavaMK 319 $2601314 dB122 dB20Hz-18kHz200
RødeNT1-A $229 255 dB137 dB20Hz-20kHz100
MXLV250 $200 1520 dB130 dB30Hz-20kHz200
Blue (Blackout) SparkSL $200 34.916.4 dB136 dB20Hz-20kHz50
Audio-TechnicaAT2035 $14922.412 dB148 dB20Hz-20kHz120
LewittLCT 240 $149 16.719 dB142 dB20Hz-20kHz100
MXLV67g HE $130 1520 dB130 dB30Hz-20kHz200
BehringerB1 $100 2013 dB138 dB20Hz-20kHz50
Audio-TechnicaAT2020 $9914.120 dB144 dB20Hz-20kHz120
MXL990 $90 1514 dB130 dB30Hz-20kHz200
AKGP120 $89 2419 dB130 dB20Hz-20kHz200
MXL770 $75 1520 dB137 dB30Hz-20kHz150
SamsonC01 $72 22.4 136 dB40Hz-18kHz200
MXLV67G $70 1520 dB130 dB30Hz-20kHz200
AKG  Perception 100 ($50)1816 dB135 dB20Hz-20kHz200
AokeoAK-70 $29 2016 dB130 dB20Hz-20kHz150
NeewerNW800 $22 12.616 dB132 dB20Hz-16kHz150
NeewerNW1500 $16.50 12.616 dB132 dB20Hz-16kHz150

Because of its  4 dB  sensitivity advantage,  Audio-Technica's  AT2035  ends up being  12 dB  less noisy than the  AT2020  (or 18 dB less noisy than the multi-pattern Behringer C-3).  Likewise at the high-end,  the  AT5040  is  8 dB  more sensitive and  15 dB  less noisy than the  AT2035.  It's twice as sensitive and  4.7 dB  less noisy than the  Equitek E100s.

The Samson C01 mic gets mixed reviews;  it's reportedly rather hissy.

Audio-Technica AT2035 (product page).
 
Blue Yeti vs. Audio Technica At2020 & Scarlett 2i2  by  Matt Kjer  (2016-02-26).
AT-2020 vs. AT-2035 Comparison  by  Bandrew Scott  (Podcastage, 2016-08-12).
Comparison tests:  AT2035, C01, C-3, sE2200aIIMP  by  Robin How  (2015-01-02).
Shootout:  Blue Spark,  Neumann U87ai,  Sennheiser MKH 416 (5:36)  Russell Cory  (WWK TV,  2013-08-13).
Blue LDC Microphones, SL Series:  Spark, Bluebird, Baby Bottle (6:09)  Jon VonRentzell,  Blue  (2017-06-21).
Lewitt LCT 240Pro vs. Audio Technica AT2035  (13:57)  by  Mike DelGaudio  (Booth Junkie,  2018-04-05).
DIY upgrades for the MXL 990  (4:24)  by  Matt  (Microphone-Parts.com,  2018-04-05).
Can you make music with a $30 Mic? (16:16)  by  Warren Huart   (Produce Like a Pro, 2016-08-30).
NW-700 vs. NW-800 vs. NW-1500 (5:15)  by  Bandrew Scott   (PodcastAge, 2016-04-29).


(2017-11-22)   Dynamic Microphones  (French:  bobine mobile)
Rugged inductive microphones,  usually with limited bandwidth.

moving-coil dynamic microphone  functions exactly as an ordinary speaker.  Actually,  a moving-coil speaker can be wired to work as a dynamic microphone,  albeit a lousy one.  Because a dynamic microphone is a passive component,  it generates no noise besides thermal  Johnson-Nyquist noise.

Unlike condenser microphones,  dynamic microphones don't require any outside  polarization voltage  to work.  There are two very different types of dynamic microphones:

As part of an old-school PA system I purchased years ago,  I got the rugged  Radio-Shack 3303043 Super-cardioid Dynamic Microphone  (RS catalog number 33-3043)  which is a perfect voice microphone in that capacity  (great proximity effect).  That unit is still available  new  on eBay, between $25 and $50 or so  (it goes for less than $20 used).  It has the exact same look and feel as the  legendary  Shure SM58S  (SM58 with a mute switch).  Both feature the exact same spherical grille  (51 mm diameter).  The built quality is the same, except that the RadioShack body is a half-inch longer and has a black grille coupling  (which is silver on the Shure unit).

Some Dynamic Microphones   (moving-coil microphones)
MakeModelPricemV/Pa HissMax.BandwidthW
SennheiserMD 441 U $899 1.8  30Hz-20kHz200
Electro-VoiceRE27 Nd $499 2.52  45Hz-20kHz150
Electro-VoiceRE20 $449 1.5  45Hz-18kHz150
ShureSM7B $399 1.1  50Hz-20kHz150
SennheiserMD 421-II $380 2  30Hz-17kHz200
Heil SoundPR 40 $308 2 148 dB28Hz-18kHz600
Electro-VoiceRE320 $299 2.5  30Hz-18kHz150
ShureSuper 55 $249 2.24  60Hz-17kHz290
RødeProcaster $229 1.6  75Hz-18kHz320
Sennheisere945 $220 2.0  40Hz-18kHz350
Heil SoundThe Fin $220 1.8 142 dB50Hz-18kHz600
ARTD7 $199 2 136 dB50Hz-16kHz250
Shure55SH II $179 1.33  50Hz-15kHz270
Golden Age ProjectD2 $150 2.5  50Hz-20kHz250
Electro-VoiceRE 635 $139 1.4  80Hz-13kHz150
ShureSM58S $104 1.3  160 dB 55Hz-14kHz270
SennheiserE835 $100 2.7  40Hz-16kHz350
Lewitt  DTP 340 TT $991.440Hz-16kHz500
sE ElectronicsV7 $99 2.0  40Hz-19kHz300
Audixi5 $99 1.6 140 dB50Hz-16kHz280
ShureSM57 $99 1.6  40Hz-15kHz310
AKGD5 $89 2.6  70Hz-17kHz600
Blue  Encore 100i $80 1.1 154 dB50Hz-16kHz150
SamsonQ7 $58 1.4 150 dB50Hz-18kHz200
ShurePGA58 $54 1.79  50Hz-16kHz150
Radio-Shack3303043 $452.5  50Hz-15kHz600
SamsonCS $40 1.7 150 dB55Hz-18kHz250
BehringerXM8500 $20 3.2  50Hz-15kHz150
PylePDmic58 $12 2.0  50Hz-15kHz600

The 33-3043 microphone was manufactured by Shure specifically for RadioShack.  So were other dynamic microphones.  All were made in Mexico and none had any direct equivalent in the regular Shure line  (they were typically loosely related to more expensive Shure models sporting the same grille).  Examples include:

  • Highball by Shure  (33-984E).
  • Shure Unidirectional Dynamic Microphone (33-3010A).
  • Omni Directional Microphone by Shure (Realistic 33-1070).

Radio Shack 3303043 User Manual
 
Behringer XM8500 vs. Shure SM58 (9:35)  by  Scott Lamp   (2017-05-23).
I bought a counterfeit mic so you won't have to (16:20)  by  Mike DelGaudio  (Booth Junkie,  2017-11-03).
Shootout:  SM7, MD421, RE20, SM57 and Audix i5 (14:26)  by  JustinSonicScoop  (B&H,  2016-02-24).
 
Audio transformers


(2018-02-04)   Ribbon Microphones
A very special type of dynamic microphone.

The  engine  (or  motor)  of a ribbon microphone is a very thin corrugated strip of metal  (usually aluminum)  which fits tightly between very strong magnets without touching them  (today, neodymium magnets are used).  The ribbon thus separates two symmetrical cavities formed by the walls of the magnet.  As the ribbon moves in response to sound pressure,  a tiny electromotive force appears between its extremities which are connected to the primary windings of a step-up audio transformer.

The natural acoustical symmetry of such microphones translate into a figure-8 directional pattern.  They pick up sound equally well from the front or the back and very little from the perpendicular directions.

Ribbon microphones include legendary  lip microphones  like the  Coles 4104  for dramatic voice reporting in very loud environments.

Examples of Ribbon Microphones   (special type of dynamic microphones)
MakeModelPricemV/Pa HissMax.BandwidthW
AEAA440 $5220 216 dB136 dB20Hz-15kHz92
Coles4038 $1332 5.6 125 dB30Hz-15kHz300
RoyerR-121 $1295 3.2 135 dB30Hz-15kHz300
AEAR84 $1035 2.5 165 dB20Hz-20kHz270
MesanovicModel 2 $999 2.217 dB140 dB20Hz-20kHz250
Audio-TechnicaAT4080 $9991122 dB150 dB20Hz-18kHz100
RødeNTR $799 315 dB130 dB20Hz-20kHz200
Coles4104 $726 3.2 120 dB60Hz-12kHz300
Audio-TechnicaAT4081 $6997.925 dB150 dB30Hz-18kHz100
sE Electronics  Voodoo VR2 $4991020 dB135 dB20Hz-18kHz200
sE Electronics  Voodoo VR1 $3991.617 dB135 dB20Hz-18kHz300
sE Electronics  se X1 R $2491.7 135 dB20Hz-16kHz200
CAD Audio  Trion 7000 $2392.2  25Hz-10kHz940
MXLR144 $82 1.6 130 dB20Hz-17kHz250

Modern ribbon microphones come in two different flavors:

  • Traditional  passive  ribbon microphones, with sensitivities below 6 mV/Pa.
  • Active  ribbon microphones, with phantom power and higher sensitivities.

In the above table,  the listed sensitivities indicate which is which.

Ribbon microphones
 
AEA ribbon microphone (5:00)   How it's made   (2012-10-27).
DIY Ribbon Microphone (7:16)  by  Fred Gabrsek   (FreddysFrets, 2012-12-17).
Royer ribbon microphones (6:23)   How stuff's made   (Discovery Channel, 2009).
Royer Labs R-Series Ribbon Transducer (7:49)  by  John Jennings   (Royer Labs, 2017-01-06).
Steve Levine interview:  Ribbon Microphones (7:41)  Audio Technica   (2011-11-13).
Royer 121, Mesanovic 2, AEA R84, Coles 4038 (41:56)  by  Warren Huart   (2016-10-06).


(2018-02-14)   End-address small-diaphragm microphones:
Without  interference tubes,  they're less  directional  than  shotgun  mics.

Small-diaphragm condenser microphones generate more noise than large-diaphragm  ones but they are arguably superior in every other respect.

Pencil-types are often available  (only)  as matched pairs.

Some small-diaphragm end-address condenser microphones :
MakeModelPrice mV/PaHiss Max.BandwidthW
AKGC636 $499 5.620 dB150 dB20Hz-20kHz200
AKGC535 EB $350721 dB 20Hz-20kHz200
CADe70 $299 1119 dB134 dB20Hz-20kHz85
ShureBeta 87a $249 2.423 dB142 dB50Hz-20kHz120
RødeNT5 $219 12.616 dB143 dB20Hz-20kHz100
LewittLCT 140 $199 9.219 dB143 dB30Hz-20kHz150
RødeM3 $149 1021 dB142 dB40Hz-20kHz200
RødeM5 $199/2 2019 dB140 dB20Hz-20kHz200
LyxProSDPC-2 $100/2 12.630Hz-18kHz
SamsonC02 $84/2 1022 dB134 dB40Hz-20kHz200
BehringerC-2 $60/2 8.919 dB140 dB20Hz-20kHz75

LYX Pro SDPC-2 Rode M5 Comparison (4:21)  by  James Tyler  (2016-12-17).
3 Cheap Mics for Interior Dialog (4:26)  by  Jeff Ello  (2017-02-10).


(2018-02-02)   Shotgun Microphones
Small-diaphragm condenser microphones with high directivity.

A shotgun microphone consists of a standard standar capsule monted at the rear of a long  interference tube  with a number of slots on it.  On-axis sound passes through the tube unimpeded or theough the different slots in phase  (constructive interference).  On the other hand,  destructive interference attenuates off-axis waves as they pass through the slots with different phases.

Because of their natural cylindrical shape,  shotgun microphones often feature a compartment for a single AA battery to power them as an alternative to  phantom power  (units primarily intended for use with DSLR or  hybrid cameras  don't even allow phantom power).

According to the specifications of  Røde  and other manufacturers,  the battery  must  be a  1.5V  cell  (i.e.,  a single-use alkaline battery).  A rechargeable NiMH battery has a nominal voltage of only  1.2V,  which makes it unsuitable.  A well-conditoned fully-charged NiMH cell may work at first  (the initial voltage of a freshly-charged battery is about  1.46V)  but it will struggle and fail very soon.  You've been warned.

The  Audio-Technica  models  AT4071a  and  AT4073a  are discontinued.  They've been superseded by the  BP4071  and  BP4073,  respectively.

Some shotgun microphones :
MakeModelPrice mV/PaHiss Max.BandwidthW
SchoepsCMIT 5 $2199 1714 dB132 dB40Hz-20kHz50
DPA4017B $1800 1925 dB133 dB20Hz-20kHz150
SennheiserMKH 60 $1500 408 dB125 dB50Hz-20kHz150
SankenCS3-e $1350 5015 dB120 dB50Hz-20kHz120
SennheiserMKH 8060 $1250 6311 dB129 dB50Hz-25kHz25
Sennheiser MKH 416 $999 2513 dB130 dB40Hz-20kHz25
Audio-TechnicaBP4071 $799 35.513 dB141 dB20Hz-20kHz50
AT4071a 89.112 dB124 dB30Hz-20kHz100
Audio-TechnicaBP4073 $699 35.513 dB141 dB20Hz-20kHz50
AT4073a 70.814 dB126 dB30Hz-20kHz100
RødeNTG3 $699 31.613 dB130 dB40Hz-20kHz25
SennheiserME 66 $460 5010 dB125 dB40Hz-20kHz200
RødeNTG4+ $399 2516 dB125 dB40Hz-20kHz200
RødeNTG4 $369 2516 dB135 dB40Hz-20kHz200
AputureDeity $359 2512 dB130 dB50Hz-20kHz75
SennheiserMKE 600 $330 2115 dB132 dB40Hz-20kHz 
RødeNTG2 $269 1518 dB131 dB20Hz-20kHz250
RødeNTG1 $249 1518 dB139 dB20Hz-20kHz50
Audio-TechnicaAT897 $249 1017 dB129 dB20Hz-20kHz200
AzdenSGM 250 $229 12.617 dB132 dB20Hz-20kHz120
Audio-TechnicaAT875r $169 31.620 dB127 dB90Hz-20kHz100
VidProXM-88 $90 12.6100Hz-16kHz1 k
XM-55 $78 5.6100Hz-16kHz1 k
Boya  BY-PVM1000 $65 12.614 dB 25Hz-20kHz380
MarantzSG-5B $36 17.834 dB120 dB200Hz-16kHz250

A few comments are needed about the bottom of that table,  which lists low-end consumer product,  as the listed prices indicate:

The  VidPro  models  (14-inch XM-88 and 10-inch XM-55)  come with plenty of accessories  (each as a 13-piece kit in a molded case).  Their noise figures are undisclosed by the distributor.  The audio quality is modest but either microphone can be very cost-effective,  as it can be plugged directly into the 3.5 mm socket of a DSLR  (cable included)  running off its own internal AA battery.  They can also use XLR phantom power.

The BY-PVM1000 is consistently reported to suffer from crackling noises when operated off 48V phantom power.  This problem is reported in some written reviews and can be heard even in favorable video reviews.  That seems to be a design flaw present in all units  (it may be caused by capacitors with borderline voltage ratings).  Not recommended at all for use with 48V phantom power  (and audio quality is downrated on battery power).  Could be OK with 24V phantom power,  who knows?

The cheapest XLR shotgun microphone,  sold as  Marantz SG-5B,  is just adequate for experimentations and educational projects  (dissecting a microphone).  It has been on sale at $16 or less.  Its restricted bandwitdth and high noise make it unsuitable for any type of video production.  (It's apparently not a fake; the official Marantz site does report the poor specs.)

For completenes,  the  Neewer  bargain brand also sells short (10") and long (14.37") shotgun microphones on the cheap  (for $23 and $24,  respectively).  They can't use phantom power and will work for up to  26  hours off a single  AA  battery.

How Shotgun Microphone Work  by  Hugh Robjohns  (Sound on Sound, Dec. 2013).
DIY Shotgun Microphone Project  by  John Heisz  (2015-08-10).
 
Marantz SG-5B;  Cheapest XLR Shotgun Mic (6:28)  by  Jordan Keyes  (2017-03-07).
Shotgun Mic Shootout:  XM-55 vs. NTG2 vs. NTG3 (3:42)  by  Christian Taylor  (2016-02-15).
VidPro XM-88 Review:  Best Microphone Bundle under $100 (7:49)  by    (TechMischief, 2016-12-18).
Shotgun Mic Shootout:  MKH416, NG4+ and XM-55 (13:38)  by  Tom Antos  (2016-07-13).
Aputure Deity Shotgun Microphone Review (8:09)  by  Curtis Judd  (2017-01-05).
Aputure Deity  vs.  Sennheiser MKH416 (6:45)  by  Tomas Villegas  (2017-01-21).
5 Shotgun Microphones:  SGM250, NTG2, Deity, NTG4+, 4017B (11:56)  Curtis Judd  (2017-03-10).
Aputure Deity Mic Review (13:30)  by  Neil Kesterson  (Media Unlocked, 2017-08-13).
Audio-Technica AT875r & AT897 vs. Sennheiser ME-66 & MKH-60 (15:11) The Video Pro Guys (2017-11-30).
 
How to use shotgun microphones (5:35)  by  Shure  (2012-04-20).


(2017-11-01)   Lavalier Microphones  (Lapel Mics) :
The best way to isolate a voice from ambient sound.

It's an unavoidable part of the  physics of sound  that tiny microphones will produce more hiss than full-sized ones.  Lavalier mics are appealing in other ways.  Draw your own conclusions.

All  commercially available lapel mics are condenser mics which need either their own battery or  plug-in power  from the audio socket,  typically from  2 V  to  10 V  (more than  10 V  may damage the mic and  48 V  will  fry it). 

Properly taking sensitivities into account,  the shocking truth which emerges from the nonexhaustive table below is that the least noisy lavalier mics are the ME2 and the Giant Squid  (the latter being only 0.2 dB behind, which isn't significant).  The MKE2,  which costs three times more than the former and eight times more than the latter,  is actually  2 dB  worse than either!  The  J 044  and the  HQ-S  are respectively  5 dB  and  10 dB  worse than the  ME2.  (I don't have data yet for the Purple Panda and the lowly Neewer.)

Noise is only part of the whole story and the less-than-stellar performance of the expensive  MKE2  in that department is entirely due to its tiny size.  The relatively low noise of the  ME2  is partly due to its limited bandwidth.

Some Omni-Directional Lavalier Microphones   (a.k.a.  Lav mics, lapel mics)
MakeModelPricemV/Pa HissMax.BandwidthW
SennheiserMKE2 $390526 dB142 dB20Hz-20kHz1 k
SennheiserME2-II $1302036 dB130 dB50Hz-18kHz 
RødesmartLav+ $60 25.541 dB 20Hz-20kHz 
Giant Squid$49 1832 dB 20Hz-20kHz 
Aspen micSHQ-S$45 6.336 dB 20Hz-20kHz 
JK®Mic J 044$29 6.331 dB   
Purple Panda$26      
SonyECM-CS3$17 12.6  50Hz-15kHz 
Neewer0077$2      

Sennheiser's cost-no-object  MKE2  is fairly bright  (+4 dB at 10kHz)  to compensate for the fact that it's normally worn under a shirt.  It comes with several caps to adjust its frequency response.

Sennheiser's mics come with locking plugs ("EW" = "Evolution Wireless").  JK's very popular  Mic-J 044  (which may well be the best value for the money)  is available with many plugs to choose from  (including Sennheiser's locking connector).  Usually,  all others only have regular TRS and/or TRRS 3.5mm audio jacks.

The Neewer 0077 microphones are extremely cheap  (I just got  three  of them for a grand total of  $4.99.)  You can't buy fewer than three at a time.  They are essentially  disposable  microphones.  They are reportedly prone to failure and are supposed to produce only junk boomy sound...  However, they're certainly  not  a total waste of money.  They do sound better than most on-camera mics.  With low expectations, I was even surprised to find the sound rather pleasant on my initial test!

New  Giant Squid Audio Lab Lavalier (2014-03-16, 3:15)  In Depth Review (17:08, 2014-02-20)  Curtis Judd.
MicJ 044 Lavalier Microphone Review:  Good sound, small price  (7:39)  by  Curtis Judd  (2014-11-13).
Aspen Mics HQ-S vs. Giant Squid and JK MicJ 044  (6:08)  by  Curtis Judd  (2015-02-09).
$2 Neewer Lapel Microphone  (3:43)  by  Jordan Keyes  (2017-06-05).

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