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 high-quality dynamic microphone; for general amplification, you can use ordinary moving coil type; when the speaker position is not available When moving or speaking, the distance from the amplifier is large. For example, karaoke, you 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 connection line
The output voltage of the microphone is very low. In order to avoid loss and interference, the connection line must be as short as possible. The high-quality microphone should be a double-core stranded metal shielded wire. Generally, the microphone can be a single-core metal shielded wire. 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 near-talk effect
Generally, the working distance between the microphone and the mouth is preferably 30cm–40cm. If the distance is too far, the reverberation increases and the noise increase relatively. If the working distance is too close, the signal will be distorted due to excessive signal, and the low frequency sound will be too heavy to affect the language. This is because the directional microphone has a "near-talk effect", that is, the low-frequency sound is significantly improved when broadcasting at a close distance.
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 larger the off angle between the two, the higher the treble loss is. 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 amplifying, 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.
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