Types Of Microphones

Dynamic Microphone

Dynamic microphones, thus, are microphones that convert sound into an electrical signal by means of electromagnetism. They fall into two categories, moving coil and ribbon microphones.

A moving coil capsule: At the back of the transparent membrane you can see the wire coil, which is surrounded by a permanent magnet.

Moving coil microphones are probably easiest to understand, because they are basically built like a loudspeaker: A coil is glued to the rear of a membrane, and there is a strong magnet surrounding this coil. When sound waves hit the microphone, the membrane moves to the rhythm of the sound waves, and the coil on its back moves along with it. The relative movement of the coil within its (stationary) magnetic gap induces a small signal voltage in this coil. There’s your microphone, a device that converts sound into an electrical signal.

• Preferred for use on stage
• Quite sturdy
• Do not require external power

*In the studio, engineers usually prefer condenser or in some cases ribbon microphones, which are less robust but offer superior sound reproduction.

A ribbon transducer: Two permanent magnets in a metal frame form a magnetic gap in which a thin aluminum ribbon can move with the sound waves.

Ribbon Microphone

Ribbon microphones work by the same basic principle of electromagnetic induction. However, instead of having a membrane and a coil, a ribbon transducer uses a narrow strip of extremely thin aluminum foil. In other words, the membrane itself is the electrical conductor that moves inside the magnetic gap. Such a thin piece of aluminum ribbon is much lighter than a membrane with a coil of copper wire attached to it. A ribbon transducer is therefore able to follow the movements of the sound waves more accurately than a moving coil capsule.

However, with just one conductor inside the magnetic gap instead of a whole coil of wire, it also produces much, much lower output. Ribbon microphones therefore contain a step-up transformer, which multiplies the transducer’s output voltage by a factor of about 30. Even so, ribbon microphones typically have lower sensitivity (i.e. output level at a given sound pressure level) than a moving coil microphone. A ribbon mic therefore requires a very low noise preamp with lots of gain.

• Ribbon mics are bidirectional 
• Equally sensitive to sound coming from the front and back. 
• Sound waves coming from the sides do not set the ribbon in motion. 
• Pickup pattern is called figure-8.
• Very fragile and must be treated with great care
• Treble response of most ribbon mics is quite limited

*Today, ribbon mics are used for special applications, only, where extended top end is not required, e.g. for guitar cabinets, or not wanted, e.g. to tame overly bright brass instruments.

A relatively new development are so called active ribbon microphones, which contain an amplifier circuit for higher output. Active ribbon mics require phantom power, just like condenser microphones.

Condenser Microphone

Condenser microphones have always been the preferred type for studio recording.

A condenser microphone capsule with a gold sputtered mylar diaphragm.

The backplate consists of solid brass with a hole pattern that must be drilled with extreme precision for consistent sound.

The British call them “capacitor microphones”. A capacitor is essentially two metal plates in close proximity. The closer they are, the higher the capacitance.

A condenser capsule is constructed similarly. It consists of a thin membrane in close proximity to a solid metal plate. The membrane or diaphragm, as it is often called, must be electrically conductive, at least on its surface. The most common material is gold-sputtered mylar, but some (mostly older) models employ an extremely thin metal foil.

When sound waves hit the diaphragm, it moves back and forth relative to the solid backplate. The distance between the two capacitor plates changes. As a result, the capacitance changes to the rhythm of the sound waves and it converts the sound into an electrical signal.

The capsule signal itself, however, is much too “fragile” to be connected to other pieces of gear. The condenser capsule’s output voltage is actually quite high, but it produces almost no current, because so little energy is stored in this small capacitor. It requires what is called an “impedance converter”, a circuit that buffers between the capsule and the outside world. The impedance converter makes the signal more “sturdy” by making more signal current available.

Condenser microphones therefore require external power P48 phantom power.

Due to their low-mass diaphragm, condenser microphones have superior transient response.

Due to its extremely low mass, the diaphragm of a condenser microphone can follow the sound waves more accurately than that of a dynamic microphone with a (relatively) heavy moving coil attached. Condenser microphones, therefore, offer superior sound quality. Of all microphone types, condensers have the widest frequency response and the best transient response (transients are fast bursts of energy, e.g. the attack of a drum   or the “pick” of an acoustic guitar). Also, condenser microphones usually offer much higher sensitivity (i.e. output) and lower noise than dynamic microphones.

Sound Sample

Dynamic Microphone 

Ribbon Microphone

Dynamic Microphone

Condenser Microphone