Why generally speaking, people are more inclined to choose condenser microphones than dynamic microphones? This question may have been confusing you. In this issue, let’s take a look at the difference between dynamic microphones and condenser microphones.
Dynamic microphones and condenser microphones have different energy conversion methods. Although the conversion method of condenser microphones is more advanced in terms of technology, it does not mean that condenser microphones are always a better choice.
Almost all microphones use a physical diaphragm to sense subtle changes in the air pressure/velocity that carries sound waves. The lighter the diaphragm, the more sensitive it is—the less energy required for movement—and the easier it is to change direction during movement. Therefore, the lighter the diaphragm, the better the high-frequency response and transient response of the microphone.
About dynamic microphones
In a dynamic microphone, a large metal block is stuck behind the diaphragm. The metal block is wrapped by copper wire (or aluminum wire), and a permanent magnet is placed around it. A long time ago, Michael Faraday explained how the movement of a wire in a magnetic field generates current, which is why a moving coil microphone can output a wave current similar to a sound wave. Of course, these metal blocks stuck to the back of the diaphragm will undoubtedly make the diaphragm heavy, which will increase the inertia of the diaphragm and reduce the sensitivity of the diaphragm-so the high frequency extension of the dynamic microphone is relatively weak. The transient response is also poor. But this is not necessarily a bad thing.
For example, many recording engineers prefer to use dynamic microphones when recording close-up drumming, because their limited transient response is like a compressor, which ignores the fastest transients, and outputs a denser and more susceptible output. Control the sound, and will not produce transient peaks like condenser microphones. This is also true when recording some heavier acoustic guitar parts, and it is also used in some special vocal songs.
In addition, it should be clear that the above statements are just a general cognition-there are some high-quality dynamic microphones that have a frequency response that is not inferior to that of condenser microphones. There is another form of "moving coil microphone" (a type of microphone based on electromagnetic principles) that is also very powerful: aluminum ribbon microphone, which still generates current output through the movement of a conductor in a magnetic field, but this conductor is the diaphragm itself , Usually a very thin aluminum foil strip. This kind of aluminum foil strip is very light, so the inertia is small, and the frequency and transient response are also greatly improved. Sensitivity is naturally the same. Unfortunately, the conductor in the magnetic field has only one path (and there are many possible conductor paths in the coil), so the current generated is very small and the output is relatively low. Therefore, it is necessary to increase the gain to increase the usability of the signal, but this also means that there will be more problems such as electrical noise.
About condenser microphones
Assuming that all condenser microphones work on the principle of static electricity, the metal diaphragm is equivalent to a plate of a "capacitor". Just in case you don’t know it yet, just explain: a capacitor consists of two conductive plates arranged in parallel, separated by a medium called a "dielectric" (in short, air). It will store charge, the stored charge (Q), the distance between the plates (defined as capacitance, C), and the voltage across the capacitor (V). The relationship between the three can be expressed by a formula: Q= CV. If the back plate is fixed and the front plate is a diaphragm, any slight movement of the diaphragm caused by sound waves will change the size of the capacitance. If the amount of charge stored in the dielectric remains constant, then the voltage across the capacitor will be proportional to the required sound.
The most common type is called "DC-biased condenser microphone". The charge stored in the capacitor capsule is controlled and maintained by an external voltage (usually 60V) applied between two capacitor plates by a large resistor. The impedance conversion circuit (usually using a vacuum tube or FET) detects the capacitance change as a voltage change at both ends of the capacitor and converts it into a stronger signal that can be transmitted to the output line. This "impedance conversion circuit" is very critical because it is located around the diaphragm and maintains a very high impedance to prevent the stored charge from leaking. At the same time, it must maintain a very low source impedance for the output cable so that the signal can be It is transmitted to the mic preamp with almost no loss.
Like the ribbon microphone, there are no additional items on the diaphragm of the condenser microphone, so it is very light and has excellent frequency range and transient response. It is also very sensitive to low frequencies and can produce a relatively high output level, so it does not need to increase the gain as a typical dynamic microphone.
Therefore, it is generally believed that the condenser microphone is technically superior to all other forms of microphones-it provides the better technical specifications and accuracy that should be possessed as an electro-acoustic transducer. This is why condenser microphones are often called "better studio microphones".
However, strictly speaking, whether it is from the actual demand level or the artistic level, the better is not necessarily the most suitable.