Small diaphragm omni-directional capacitor microphone with a
½” measurement grade capsule with a nickel diaphragm

  • Small diaphragm ½” measurement capsule
  • Metal (nickel) diaphragm with a thickness of just 0.9 microns
  • Pressure transducer
  • Free field equalization
  • 200V capsule bias voltage (via DC-DC converter from 48V phantom power)
  • Transformerless

“Not only is this a remarkably high-quality microphone,
but a very versatile one too, thanks to some cunning
acoustic trickery…” … “I fear I may have just become
completely infatuated with the M221!”
Hugh Robjohns, Sound On Sound, June 2013

The capacitor microphone M 221 unifies universal small diaphragm capsule technology with a metal diaphragm and a modular preamplifier. The use of a certificated measurement capsule combined with a preamplifier with 48 V phantom powering reaches a constant magnitude and phase response and transmission properties which are long-term stable.
Because of the small capsule dimensions the M 221 is ideally suited for applications where a low interference with the sound field is demanded. It is usable as a main microphone for recordings which should include a certain amount of the room response. As well the M 221 is suited as a spot microphone for recording instruments very close where the low frequencies should be transmitted in detail and original. Moreover it can be used for multi-channel main microphone arrangements like AB stereophony or Decca Tree. For these applications the microphone is ideal because of its precise and long-time stable transmission properties. The M 221 has an excellent transient response because of the pressure transducer capsule and is really suitable to record instruments with extreme transients. With the both different sized  APE spheres a high frequency accentuation can be produced in an acoustical way to increase the presence and to compensate the high frequency roll-off in the diffuse sound field.

The capsule’s frequency response goes down to 3.5Hz (-2dB) – with the phantom powered body the lowest useable bass frequency would be about 10Hz.

How you attach the KA3 / KA4 APE spheres (frequency balls):
NB: It is important that the whole capsule is removed to install/remove the APE sphere and NOT the protective cap as removing the cap could damage the diapgragm if not done properly

The M 221 can operate also in unfavorable climate conditions, especially in reference to temperature and air humidity,  for which the optional TA 202 Dehumidifier is available

Acoustic Specifications

This is an end-address microphone. The sound transducer is a condenser capsule with a diameter of 12.5 mm and with an ultra-thin nickel metal diaphragm that has a thickness of only 0.9 micron and is “grown in place”. The pressure transducer capsule exhibits an omni-directional polar pattern without proximity effect. Because of the free field equalization the M 221 has a constant frequency response from 3.5 Hz up to 20 kHz (± 2 dB). The static pressure equalization between the capsule interior and the atmosphere goes through a vent to the preamplifier. Therefore the humidity adaptor TA 202 is usable to protect the microphone in application with high air humidity. The use of the M 221 with the KA 3 APE sphere effects a frequency response accentuation which begins at approximately 1 kHz and goes constant at 3 dB from approximately 4 kHz up to 12 kHz. With the KA 4 APE sphere  the accentuation of the high frequencies starts also at approximately 1 kHz and goes constant at 3 dB between 3 kHz and 12 kHz.

MK 221 capsule

The MK 221 is a special capsule originally developed for critical measurement applications.  The microphone capsule is designed and very carefully constructed to ensure excellent long-time stability of the electroacoustical parameters. All essential components including the diaphragm are made of nickel and the diaphragm is bonded by a special galvanic process. The rear electrode is insulated from the cartridge housing by a quartz glass plate. The nickel diaphragm is actually grown in place as one uniform piece and is the same in all directions; it is just 9/10µ thick – much thinner than normal diaphragms.

Electrical Specifications

The transformerless circuit design of the electronic impedance converter with symmetrical output facilitates an output capability for sound pressures from15 dB(A) up to 136 dB with a maximum of 0,5 % THD (total harmonic distortion). The microphone is connected by a standard 3-pin XLR-male plug with gold-plated pins which realizes the powering by an external 48 V phantom supply according to IEC 61938 with a current consumption of 6 mA.

Mechanical Specifications

The M 221 consists of a microphone capsule and a microphone preamplifier as independent mechanic parts which are connected to a complete microphone through a screw thread. Microphone capsule and microphone preamplifier have an identical overall diameter of 12.7 mm which enlarges to 21 mm over the length of the microphone preamplifier to the connection side of the microphone. The shape of this enlargement is designed for a minimum interference with the sound field. Microphone capsule and microphone preamplifier have together a length of 170.4 mm. On the connection side of the M 221 there are standard microphone holders mountable. To reach a higher attenuation against solid-born sound and impulses there are elastic holders and suspensions usable. The weight of the M 221 is 123 g what allows to use the microphone with stand mountings as well as to hang up the microphone from the ceiling without any problems.

Matched Sets

The M 221 can be supplied in matched stereo pairs on request – also available on request are matched sets of 3 or 5 for Decca Tree or Surround recording use.

Finish: dark bronze

A Brief History of Microtech Gefell

M 221 Data Sheet

Sound On Sound review of the M 221

Supplied complete with:
Microphone holder – MH 93.1
3cm APE frequency ball – KA3
4cm APE frequency ball – KA4
Wooden box

Optional accessories:
Windscreen – W 2
Elastic suspension – MH 93 dark bronze
XLR cable, 10m – C 70
TA 202 dehumidifier


Frequency Response & Polar-Pattern

Frequency Response – showing the effect of the KA3 and KA4 APE frequency balls