Introduction

Sennheiser offers a range of microphones supported by cutting-edge technology, which ensures great, reliable results in every situation.  These consist of dynamic, back-electret condenser and RF condenser microphones.

Dynamic Microphones

Dynamic microphones fall into two main groups: ribbon and moving coil.  All Sennheiser dynamic microphones work on the more rugged moving coil principle, which can be used in difficult working situations where more fragile microphones would not be suitable.  These microphones are mainly applied to broadcast reporting situations and live stage work.

Within a moving coil dynamic microphone, a coil of wire connected to the microphone diaphragm is held in a magnetic field.  Sound waves change the pressure of the air they travel through, which causes the diaphragm to vibrate. This causes the coil to move in the magnetic field, which induces an audio frequency. This signal is balanced, grounded and of low resistance, and can be connected directly to the microphone input of a tape recorder or mixing console without any electronics or supply voltage needed in the microphone.

Back-Electret Condenser Microphones

Condenser microphones use a variable plate capacitor as an acoustic transducer, with the front electrode as the microphone's diaphragm.  As it moves, the capacitance changes, and a voltage proportionate to the acoustic signal is produced.

The electrodes used in pre-polarized condensers are manufactured from a special synthetic material known as the "electret".  This material has a unique quality, in that it permanently stores an electrical charge; the charge is "frozen" in the electret material.  Therefore, it requires no high external polarizing voltage and can be powered by low voltage internal batteries.

In the Sennheiser range of back-electret condenser microphones, only the stationary back electrode "black plate"- is used as the charge carrier.  The counter electrode, manufactured from a gossamer-thin foil (3.5 µm), is made conductive by applying a thin layer of gold with a vapor-coating process.  This ultra-light diaphragm (approx. 100 µg) has a good transient response and high sensitivity as low sound pressure levels off.  It also ensures highly accurate sound reproduction with minimal distortion.

In contrast to dynamic microphones, back-electret condenser microphones can be very compact.  This makes it possible to design miniature, clip-on lavaliere microphones, and to use capsules for shotgun microphones of variable directivity factors.

RF Condenser Microphones

RF Condenser microphones constitute a unique, sophisticated class of condenser microphones.  They fulfill the very highest demands made on sound quality and versatility, and are renowned for their high quality, accurate sound reproduction, ruggedness, all-weather operation, wide frequency response and extremely low inherent self-noise.

Usually, a high capsule polarization voltage would be necessary; however, RF condenser microphones use a comparatively low RF voltage, which is generated by a low-noise oscillator.  It is modulated by the capacitance changes produced by the sound waves moving the capsule diaphragm.  Following the demodulation, a low-noise audio frequency signal with very low source impedance is available, which can be used to directly drive 'ordinary' bipolar transistors.

As bipolar transistors produce less random noise than the field-effect transistors usually needed, electrical equalization technology can be included to increase the microphone's dynamic range and linearize its frequency response.  As a result, an excellent low frequency response can be achieved even with small capsules, which would normally only be possible using larger capsules.  In addition, small capsules achieve a considerably better high frequency response than large capsules.

The RF process results in a considerable reduction of the electrical impedance of the capsule and enables RF condenser microphones to be operated in all weather conditions.  A further advantage of this process is that an ungrounded audio frequency signal is available although the capsule is grounded.  This is why all RF condenser microphones possess a genuine fully floating, balanced output without an audio frequency transformer.

Dynamic Features

	Connections All Sennheiser dynamic microphones are fitted with a standard 3-pin XLR connector. (Diagram here) This is wired so that a positive sound pressure on the diaphragm produces a positive voltage at pin 2 compared with pin 3.  Pin 1 is the ground - or screen - connection.
	Description of Models MD... Microphones with the prefix MD are good general purpose microphones for studio and stage use. COM These microphones are designed for use in conference and communications situations.   e... evolution microphones are designed specifically for live stage applications.
	Pick-up Patterns Sennheiser dynamic microphones are available with three different pick-up patterns (omni-directional, cardioid, and super-cardioid).  These are illustrated to the left.

Back-Electret Features

	Powering The impedance converters and low-noise amplifier circuits used in Sennheiser's back-electret condenser microphones are powered by an integral battery, a Sennheiser radio transmitter, a power supply adaptor, phantom powering (XLR-3), or an external power supply.
	Description of Models MKE... Back-electret condenser microphones can be identified by the inclusion of the letters MKE in their model number. ...-C Variants delivered without accessories, a carrying case or protective pouch. ...-2R Variants in the -2R range are powered via the SK 2012 pocket radio transmitter. ...-4 Variants in the -4 range are powered via the SK 50, SK 250, SK 5012 or SK 3063 pocket radio transmitters. ...-5 Variants in the -5 range normally have open-ended cables. ...-60 Variants in the -60 range and the ME 62-67 range of microphone heads are powered via the K6 or K6P powering modules. ...-P Variants in the P range are fitted with a 3-pin XLR connector, which can be connected directly to phantom powering (DIN IEC 268-15) 12 to 48 V. COM These microphones are designed for use in conference and communications situations. e...  evolution microphones are designed specifically for live stage applications.
	Pick-up Patterns The various pick-up patterns of back-electret condenser microphones are illustrated to the left.

RF Condenser Features

The MKH 20 to 80 microphones have Sennheiser's unique and revolutionary symmetrical push-pull capsule.  Besides the normal back plate, this capsule is fitted with an additional front plate, with the diaphragm positioned between them.  Both plates are acoustically transparent.  Any impedance changes in the air gaps between the diaphragm and the respective plate are opposite. Therefore, they each cancel each other out, leading to unchanging acoustic impedance. 

This balanced design produces extremely low distortion figures and a higher capsule output that gives a much lower noise figure.  The result is a microphone series unmatched in clarity and neutrality.

	Power Supply Units All RF condenser microphones use 48 V phantom powering (P 48).  The TU-3 version of the MKH 416 operates using 12 V AB (T) powering.  All models are powered externally via the microphone cable.  The MZA 14 P 48 2 (or MZA 14 TU) battery unit is available for both types of powering.
	Connections All RF condenser microphones are fitted with a 3-pin XLR connector as standard.  Standard polarity results in a positive voltage at pin 2 against pin 3, when pressure increases in front of the diaphragm.
	Pick-up Patterns The various pick-up patterns of Sennheiser's MKH RF condenser microphones are illustrated by the examples below: