What is the Difference between a Condenser and Dynamic Microphone?

Moving-coil microphone [Engineering acoustics] Moving-coil microphone (moving-coil microphone) is a device that converts sound into electrical signals. Dynamic coil microphones are made using the phenomenon of electromagnetic induction. When sound waves cause the diaphragm to vibrate, a coil (called a voice coil) connected to the diaphragm vibrates together, and the voice coil vibrates in a magnetic field, and an induced current is generated therein. (Electrical signal), the magnitude and direction of the induced current change, and the amplitude and frequency of the change are determined by the sound wave. This signal current is amplified by the amplifier and transmitted to the speaker, and the amplified sound is emitted from the speaker.

Dynamic microphone

Moving-coil microphone [Engineering acoustics] Moving-coil microphone (moving-coil microphone) is a device that converts sound into electrical signals. Dynamic microphone is using

When the microphone receives sound waves, the force generated by the sound waves acts on the diaphragm, causing the diaphragm to vibrate, which drives the voice coil to vibrate accordingly. The voice coil moves in the magnetic steel to generate electromotive force, and the sound signal is converted into an electrical signal.

The main failures of dynamic microphones are disconnection. One is the disconnection of the microphone's plug, the second is the disconnection of the microphone lead itself, and the third is the disconnection of the voice coil. The disconnection fault can be found through the ohms 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 voice coil connection, welding is difficult and sometimes even impossible to repair.

Pointing dynamic microphone

Generally divided into heart-shaped, super-cardioid, figure-eight, gun type, omnidirectional and so on.

As for what these pointers are all about, you can find a microphone to try. As shown in the figure, the direction of the arrow is directly in front of the microphone, and the dashed line is the approximate range of pickup. Outside this range, the pickup will not be sensitive. If you have the conditions, it is recommended to find a multi-directional microphone to try it out, and you can understand the meaning of the direction.

Dynamic microphone microphone impedance

Low-impedance microphones should be used in professional recording studios. Since long cables may be used for connection, low-impedance microphones can reduce signal attenuation.

Dynamic microphone balanced linear

The balanced wire consists of two wires and a shielded wire; the unbalanced wire has only one wire, and the shielded wire replaces the second wire.

The advantage of a balanced line is that the two wires of the line pick up unwanted noise signals with equal strength, so the two can cancel each other out. The unbalanced line transmits the noise signal to the next stage of the line.

If the audio signal is strong or the unbalanced line is short, noise may not be heard. However, the microphone cable is generally very long. Think about it. We pulled the cable from the recording room, passed the wall through the sound box, and then entered the tuning and recording system of the control room. Therefore, we need to use a balanced cable, and use a balanced plug accordingly: XLR, commonly known as the Canon or male and female head; or the three-core TRS.

Dynamic microphone selection

Select microphones step by step

Choosing the right microphone is becoming increasingly difficult. There are more and more types of microphones, each with its own strengths and excellent quality. Therefore, in addition to the price when buying the biggest influencing factor is personal preference. For those who prefer to rely on objective parameters rather than subjective impressions when buying, here are some tips for buying special-purpose microphones, including broadcasting, recording, or live broadcast (with or without sound reinforcement).

Smoothest response

When choosing a microphone, the user should first and foremost care about its frequency response characteristics. The frequency response must be wide enough to pick up the entire range of sound, with no audible change in the quality of the natural sound source.

The next step is to choose the polarity pattern. Among all types of microphones at the same price, omnidirectional microphones usually have the broadest and smoothest response, while also being less sensitive to breathing, hand-held noise and wind. They are ideal for most applications without excessive external noise or too much reverberation. For example, the AKG D 230 dynamic omnidirectional microphone is widely used by reporters.

Although omnidirectional microphones accept sound waves from all directions well, some users may prefer to receive sound waves from one (unidirectional) or two (bidirectional, figure-eight) directions. This means that in order to obtain the same ratio of direct sound and reverb sound, cardioid and bidirectional microphones, supercardioid microphones and supercardioid microphones are located 1.7 times from the sound source, 1.9 times and 2 times.

The electrical output impedance is important because it should match the input impedance of the mixer, tape recorder, or amplifier. This impedance unit is , usually at a frequency of 1kHz. Dynamic coil microphones have a typical impedance of 600.

As a rule of thumb, the input impedance of the device should be at least three times the microphone impedance. All mixers currently on the market meet this requirement.

In addition, there are high impedance microphones and dual impedance microphones that can be switched between low and high impedance. The length of the cable connected to the high-impedance microphone should not exceed 7m, because the cable capacitance will cause high frequency attenuation.

The built-in amplifier microphone can be plugged into any load above or equal to the minimum load impedance for operation. If the microphone is connected to an input with a load below the minimum load impedance, the frequency response will suffer.

Overload sound levels are important for condenser microphones. Condenser microphones work in a linear state up to a certain sound pressure level (SPL). This SPL is called overload or maximum SPL, and the frequency is usually 1kHz. If the sound level exceeds this value, the output signal will be deteriorated due to harmonic distortion.

At the maximum SPL, the total harmonic distortion factor should not exceed 0.5% or 1%. It is not possible to overload dynamic microphones in common applications, they never actually distort the signal.

Sensitivity is the microphone output voltage at a certain SPL. It is usually measured at 1kHz and the unit is V / Pa or dBV. At a certain gain setting, the more sensitive microphones produce louder sounds, but users should use them carefully at this time, because the feedback danger also increases proportionally.