Five important technical indicators of microphones of KTV speakers
Sensitivity is an important indicator of the microphone's acoustic-electric conversion efficiency. It is defined as: in the free sound field, the open-circuit output 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), and 1 volt and Pa is 0db. Since the sensitivity is much smaller than 1V/Pa, the sensitivity is expressed in db.
The high sensitivity of the microphone is a good thing, it can provide a higher input level to the mixer, can improve the signal-to-noise ratio, but too high its output 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 response
It is an important indicator that reflects the frequency distortion in the process of microphone electrical conversion. The ratio of the open-circuit output voltage of each frequency sound wave signal to the open-circuit output voltage of the microphone at the specified frequency under the action of a constant sound pressure and a specified angle of incidence of a microphone is called the frequency response of the microphone, expressed in decibels (db). The tolerance range of the frequency response curve of general professional microphones is 2db.
The simplified expression of frequency response is the frequency range in Hertz (Hz) and the non-uniformity range in decibels (db) at the same time.
Microphones are used in different occasions, 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 increase the brightness and clarity of the pickup. Generally, when used very close to the sound source, there will be a low-frequency boost phenomenon called "proximity effect", so it is better to have a significant 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.
Common directivity includes omnidirectional (non-directional), cardioid, super-cardioid, sharp heart, figure 8 (two-way), etc.
a. No pointing
This feature has the same sensitivity for incident sound waves in all 360o directions.
b. Heart shape
This feature is effective for sound waves incident at 180o on the front, and the sound on the back is suppressed.
c. Sharp heart
This feature has an incident angle of 110o from the front, which can suppress acoustic feedback well.
This feature has the same effect at 90o incident angle on the front and back. Generally used for stereo pickup and so on.
4. Output 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. Generally, below 1K is low impedance, and above 1K is high impedance. The sensitivity of high-impedance microphones has been improved, but it is easy to induce external interference such as hum, so the cable should not be long. For professional use such as stage performances, low impedance is basically used to avoid interference, and the cable can also be longer.
5. Dynamic range
It refers to the electrical frequency difference between the small useful signal and the large undistorted signal output by the microphone. A small dynamic range will cause sound distortion and deterioration of sound quality, so a sufficiently large dynamic range is required.
Since the microphone is used to transmit the fidelity of the human voice, it is an important device used at the forefront of audio equipment. The sound quality depends on the regular manufacturer, the best and the correct choice of the microphone, which has a lot to do.