Microphone-types and principle of operation

A microphone is one of the most common and important equipment in the recording studio. It stands on the front line facing the sound to be recorded and converts the sound wave energy generated by physical vibration into an electronic signal. The following will briefly introduce the structure and characteristics of several common microphones in recording studios.

1. Moving Coil Dynamic

The diaphragm (diaphragm) is the core component of the microphone. The function of the diaphragm is to receive the vibration of sound waves and convert these physical kinetic energy into electronic signals. Both moving coil microphones and condenser microphones are based on the principle of receiving sound through the diaphragm.

The diaphragm of a dynamic microphone receives sound pressure on the front side, and a coil is connected to the back side, and the coil is wound with a magnet. When the front of the diaphragm receives sound pressure, the vibration of the diaphragm will cause the coil to move and induce electrification with the magnet. With the strong or weak sound pressure, the degree of electrification induced by the movement of the diaphragm is also strong or weak. The microphone circuit Then the current generated by induction electrification is amplified. Compared with condenser microphones, condenser microphones require an additional power input to make the microphone operate, while moving coil microphones simply generate electromagnetic induction through the vibrating diaphragm and coil; the weight of the coil makes the diaphragm require a larger sound. It can only be driven by pressure, and it is also difficult to induce electrification due to subtle changes in sound pressure. Therefore, it is less easy to record subtle sounds, and the sensitivity is lower than that of condenser microphones. This feature makes dynamic microphones suitable for occasions that do not need to capture many details. For example, singers with poor singing skills will show many flaws when using condenser microphones. However, the use of dynamic microphones has lower sensitivity. The blemishes are less obvious.

Dynamic microphones can withstand high sound pressure, so they are often used in musical instruments with high sound pressure, such as bass drums, cymbals, etc. And its structure makes its frequency response not so flat, so there are often microphones used for specific purposes, such as the Shure Beta52, which specializes in bass drums, which is especially enhanced for low frequencies. The common dynamic microphone Shure SM57, its frequency response is particularly strengthened in the 4k~6kHz place, it has a very good performance when receiving snare drums, electric guitar speakers and vocals.

2. Capacitive Condenser

One of the characteristics of condenser microphones is that they require additional power to operate. The voice coil (Capsule) is composed of a thicker Back Plate and a thinner Front Plate, with a very small distance between the two. The Front Plate is composed of a diaphragm (Diaphragm). When the metal diaphragm receives the vibration of sound pressure, the energized circuit will produce a potential difference due to the change of the distance between the Front Plate and the Back Plate, and the induced current is amplified by the circuit to obtain sufficient Signal in order to capture.

The microphone diaphragm is a non-conductive film and then coated with a layer of metal. The thickness and weight of the metal coating will directly affect the sensitivity of the diaphragm. This process is also the reason why general condenser microphones are more expensive than moving coil microphones. . In addition, the signal of the condenser microphone is amplified by the circuit, and the thickness of the diaphragm is thinner and fragile than the diaphragm of the dynamic microphone, so the maximum sound pressure it can withstand is also smaller than that of the dynamic microphone. Conversely, the sensitivity and frequency response of condenser microphones are higher than those of moving coils, and the signal amplification circuit can also have different methods. For example, vacuum tube amplification will make the microphone sound warmer.

The high sensitivity of the capacitive type allows it to be used in vocal dubbing, or string music, and other applications that require delicate performance. There are many classic condenser microphones in the recording studio, such as Neumann U87, which are often used in vocal reception. The microphones of the AKG C414 series have very good performance on musical instruments, vocals, etc., and can be said to be a microphone for recording studios. DPA 4006 is an omnidirectional condenser microphone, which is often used for the reception of musical instruments, and more often for live performances of classical music. Manley Gold Reference is a very expensive microphone. A vacuum tube is used in the amplifier circuit, so it has the inherent warmth characteristic of a vacuum tube.

Three, ribbon type Ribbon

The principle of the ribbon microphone is the same as that of the moving coil microphone. It is electrified through the vibration of the diaphragm and the magnetic field. The difference between the two is the use of different diaphragm materials. The diaphragm material of ribbon microphones is mostly extremely thin aluminum, which is extremely fragile. If you accidentally hit or supply power, the ribbon of the microphone will be damaged. Because of its high production cost and difficult storage, it is rarely used in studios. However, due to advances in technology, the diaphragm material of ribbon microphones has made great breakthroughs. It is no longer as fragile as the diaphragms of early ribbon microphones , But in comparison, it is still not as sturdy as a dynamic microphone.

Most ribbon microphones have a Figue 8 type (Figue 8). The reason is that they are designed for electromagnetic induction. As shown in the figure, the ribbon diaphragm is located between the two magnets, so the front and back of the diaphragm are Both sides can be radioed. The sensitivity of ribbon microphones is between that of dynamic and condenser microphones, and the sound performance has a warm characteristic. It is generally used for vocal dubbing or some stringed instruments.