Selecting the microphone should be based on the occasions used and the requirements for sound quality, combined with the characteristics of various microphones. For example, high-quality recording and broadcasting, mainly requires good sound quality, should use condenser microphone, aluminum ribbon microphone or advanced dynamic microphone; for general amplification, you can use ordinary moving coil type; when the speaker position moves from time to time Or speaking with a large distance from the amplifier, such as karaoke singing, should use a single-directional, low-sensitivity microphone to reduce noise interference. The use of condenser microphones requires phantom power. Generally, the power supply voltage is specified in the technical parameters of the microphone. To select the phantom power of the appropriate voltage, the mixer is usually equipped with 48V phantom power.
Also pay attention to the use:
1. Impedance Matching When using a microphone, the output impedance of the microphone is the same as the input impedance of the amplifier. If the mismatch ratio is above 3:1, the transmission effect will be affected. For example, when a 50Ω microphone is connected to an input impedance of 150Ω, the output can be increased by nearly 7Db, but the high and low frequencies will be significantly lost.
2. The output voltage of the connecting line microphone is very low. In order to avoid loss and interference, the connecting line must be as short as possible. The high-quality microphone should be a double-core stranded metal shielded wire. Generally, the single-core metal shielded wire can be used for the microphone. The length of the high-impedance microphone transmission line should not exceed 5 meters, otherwise the high-pitched sound will be significantly lost. The connection of the low-impedance microphone can be extended to 30m–50m.
3. Working distance and close-talk effect Generally, the working distance between the microphone and the mouth is 750px–1000px. If the distance is too far, the reverberation will increase and the noise will increase relatively. If the working distance is too close, the signal will be distorted due to excessive signal. The low frequency sound is too heavy and affects the clarity of the language. This is because the directional microphone has a "near-speaking effect", that is, the low-frequency sound is significantly improved when broadcasting at a close distance. However, sometimes the singer intends to use the "near talk effect" to make the singing effect more beautiful and beautiful.
4, the angle between the sound source and the microphone Each microphone has its effective angle, the general sound source should be aligned with the microphone center line, the greater the off angle between the two, the higher the treble loss. Sometimes when using a microphone, it has a "long" sound, and when the microphone is deflected by some angle, it can be lightened.
5. Microphone position and height When the sound is amplified, the microphone should not be placed close to the speaker or aligned with the speaker, otherwise it will cause howling.
The height of the microphone should be determined according to the height of the sound source. If it is a person speaking or a few people singing, the height of the microphone should be consistent with the mouth of the singer; when the number of people is large, the microphone should be placed at the average height and the singer should be properly allocated. And the accompaniment and the position of the various instruments in the team, do not make the sound loud, light and light, and make all the sounds within the effective angle of the microphone. If there is a lead singer or lead, a dedicated microphone should be placed if necessary.
When several microphones are needed at the same time, the method can be taken and connected, but attention must be paid to the phase problems of several microphones. When the phases are consistent, they can be connected in parallel with each other, otherwise they will interfere with each other, so that the output is reduced and distorted. Microphones of different models and different impedances should not be used in parallel because the high-impedance microphone is “short-circuitedâ€, which causes the output voltage to drop to a very low level. Under normal circumstances, the microphones are used directly in parallel, which is not as effective as a single microphone.
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