How to diagnose and deal with dynamic microphones
The main fault of the moving coil microphone is disconnection, one is the disconnection at the plug of the microphone, the other is the disconnection of the microphone lead itself, and the third is the disconnection at the voice coil. The disconnection fault can be found through the ohm gear of the multimeter. The solution to the broken wire fault is to re-solder the broken wire. When the broken wire is broken at the connection of the voice coil, it is difficult to weld, and sometimes even impossible to repair.
Microphones are generally classified by the way in which they convert energy. Here we still classify microphones into dynamic microphones and condenser microphones according to the most common classification method for microphones in recording studios.
Dynamic microphones are microphones that generate electrical signals from conductors moving in a magnetic field. It is the diaphragm that drives the coil to vibrate, so that the coil in the magnetic field induces a voltage. Features: firm structure, stable performance, durability and low price; good frequency characteristics, flat amplitude-frequency characteristic curve in the frequency range of 50-15000Hz; good directivity; no need for DC working voltage, easy to use and low noise.
The diaphragm of this type of microphone is an electrode of the capacitor. When the diaphragm vibrates, the distance between the diaphragm and the fixed rear plate
changes, resulting in a variable capacitance. This variable capacitance is the same as that of the microphone itself. The preamplifiers together generate the signal voltage. Features: good frequency characteristics, flat amplitude-frequency characteristic curve in the audio range, which is better than dynamic microphones; no directionality; high sensitivity, low noise, soft timbre; relatively large output signal level, low distortion, transient response The performance is good, which is the advantage that the dynamic microphone cannot achieve; the working characteristics are not stable enough, the low-frequency sensitivity decreases with the increase of use time, the service life is relatively short, and the DC power supply is required for operation, which makes it inconvenient to use.
There is a preamplifier in a condenser microphone, of course, there must be a power supply. Due to the volume, this power supply is generally placed outside the microphone. In addition to supplying the polarization voltage to the diaphragm of the capacitor, it also supplies the necessary voltage to the tubes or transistors of the preamplifier. We call it phantom power. Due to this preamplifier, condenser microphones are relatively sensitive. Some of the necessary accessories for use are: shock mounts (usually given with the microphone), windscreens, blowout covers, and high-quality microphone stands. If you want to do ultra-close-up recording work, a pop shield is essential.
Dynamic microphone characteristics
1. The direction of the dynamic microphone
Generally divided into cardioid, supercardioid, figure 8, gun, omnidirectional and so on.
As for what these directions are, you can try it out with a microphone. As shown in the figure, the direction of the arrow points to the front of the microphone, and the dotted line is the approximate range of sound pickup. Outside this range, the pickup will be insensitive. If you have the conditions, it is recommended to find a multi-point microphone to try it out, and you can understand the meaning of the pointing.
2. Impedance of the microphone
Professional studios should use low-impedance microphones, which can reduce signal attenuation due to the potential for long cables to connect.
3. Balanced linearity
A balanced line consists of two wires and a shielded wire; an unbalanced wire has only one wire, and the shielded wire is used instead of the second wire.
The advantage of a balanced line is that the two conductors of the line pick up the unwanted noise signal equally, so they cancel each other out. Unbalanced lines, on the other hand, transmit the noisy signal to the next stage of the line.
If the audio signal is strong or the unbalanced line is short, the noise may not be heard. But the microphone cable is generally very long. Think about it, we pull the cable from the recording room, pass the sound box through the wall, and then enter the tuning and recording system in the control room. Therefore, we have to use a balanced line and use a balanced plug accordingly: XLR, commonly known as Canon or male and female; or TRS with three cores.