The microphone of KTV speakers has five important technical goals
Sensitivity is an important target that expresses the microphone's acoustic-electric conversion efficiency. It is defined as: in the free sound field, the open-circuit input voltage measured when the microphone frequency is 1KHz and the constant sound pressure is in the forward direction of the sound source (that is, the sound incident angle is zero). The unit is millivolt/Pa. 1Pa=10bar1ubar is roughly equivalent to the sound pressure of a person's normal speaking volume, measured at a distance of 1m.
The sensitivity of the moving coil type is about 1.5-4 mV/Pa, while the sensitivity of the capacitive type is about 10 times higher than that of the moving coil type, about 20 mV/Pa.
Microphone sensitivity is also expressed in decibels (db), the rule is 1 volt and Pa is 0 db. Since the sensitivity is much smaller than 1V/Pa, the sensitivity is expressed in db.
The high sensitivity of the microphone is a bad thing, it can provide a higher output level to the mixer, can improve the signal-to-noise ratio, but too high its input voltage is also high, prone to excessive distortion.
When used for karaoke singing, the distance between the microphone and the mouth is very close, so the sensitivity requirements are not high.
2. Frequency echo
It is an important target that reflects the frequency distortion in the process of microphone electrical conversion. The ratio of the open-circuit input voltage of each frequency sound wave signal to the open-circuit input voltage of the regular frequency microphone under the constant sound pressure and regular incident angle of the microphone is called the frequency response of the microphone, expressed in decibels (db). The tolerance range of frequency response curve of general professional microphone is 2db.
The simplified expression of frequency response is the frequency range in Hertz (Hz) and the range of unevenness in decibels (db) at the same time.
The microphones are used in different places, and the required frequency response range and unevenness range are also different.
Dynamic microphones often do not take a flat frequency response curve, but a slight increase in the high frequency range (3 ~ 5KHz), which can add the brightness and clarity of the pickup. Generally, when it is used very close to the sound source, it will present a low-frequency boosting scene called "close talk effect", so it is best to have a distinct attenuation in the low frequency range below 150Hz.
3. Pointing characteristics
The characteristic that the microphone sensitivity changes with the incident direction of sound waves is called directivity. It is often represented by a pointing graph.
The rare directivity includes omnidirectional (non-directional), cardioid, super-cardioid, sharp heart, figure 8 (two-way), etc.
a. No pointing
This feature has the same sensitivity to all sound waves incident in 360o directions.
b. Heart shape
This feature is invalid for the 180o direction of the front side sound wave incident, and the back side sound is suppressed.
c. Sharp heart
This feature has an incident angle of 110o from the front, and it is the best to suppress the acoustic response.
This feature has the same effect on the front and back of the 90o incident angle. Commonly used for plane sound pickup, etc.
4. Input impedance
Refers to the AC internal resistance of the microphone, measured with a frequency of 1KHz and a sound pressure of 1Pa. It is often divided into low impedance and high impedance. Normally 1K or less is low impedance, and more than 1K is high impedance. The sensitivity of high-impedance microphones has improved, but it is easy to induce external disturbances such as hum, so the cable should not be long. The stage performance and other professional uses basically use low impedance to not cause disturbance, and the cable can also be longer.
5. Static range
It refers to the electrical frequency difference between the minimum useful signal and the maximum undistorted signal input by the microphone. The small static range will cause sound distortion and deterioration of the volume, so a sufficiently large static range is required.
Since the microphone is used to transmit the fidelity of the human voice, it is an important device used in the forefront of audio equipment. The quality of the sound depends on the manufacturer, famous brand, and correct selection of the microphone, which has a lot to do with it.