The choice of microphone should be based on the occasion of use and the requirements for sound quality, combined with the characteristics of various microphones, and comprehensive consideration should be given to the selection. For example, high-quality recording and broadcasting mainly require good sound quality. Condenser microphones, ribbon microphones or high-quality moving coil microphones should be used; for general sound reinforcement, ordinary moving coil microphones can be used; when the speaker's position is irregular When moving or speaking, there is a large distance from the amplifier, such as karaoke singing, a unidirectional, low-sensitivity microphone should be used to reduce noise interference. The use of condenser microphones requires phantom power supply. Generally, the power supply voltage is stated in the technical parameters of the microphone. It is necessary to select a phantom power supply with an appropriate voltage. The mixer is generally equipped with 48V phantom power supply.
It should also be noted in use:
1. Impedance matching
When using a microphone, the output impedance of the microphone is the same as the input impedance of the amplifier, which is a better match. If the mismatch ratio is more than 3:1, the transmission effect will be affected. For example, when a 50Ω microphone is connected to an amplifier with an input impedance of 150Ω, although the output can increase by nearly 7Db, the high and low frequencies will suffer significant loss.
2. Connecting line
The output voltage of the microphone is very low. In order to avoid loss and interference, the connecting wire must be as short as possible. For high-quality microphones, you should choose a twisted pair metal shielded wire. Generally, a single-core metal shielded wire can be used for a microphone. The length of the high-impedance microphone transmission line should not exceed 5 meters, otherwise the treble will be significantly lost. The low-impedance microphone connection can be extended to 30m-50m.
3. Working distance and proximity 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 the strong signal, and the low-frequency sound will affect the language. The clarity. This is because the directional microphone has a "close-talking effect", that is, the low-frequency sound will be significantly improved when speaking at a close distance. However, sometimes singers deliberately use the "proximity effect" to make the singing effect more beautiful and pleasant.
4. The angle between the sound source and the microphone
Each microphone has its effective angle. Generally, the sound source should be aligned with the center line of the microphone. The greater the deflection angle between the two, the greater the treble loss. Sometimes when the microphone is used, there is a "rumble" sound. At this time, you can reduce it by deflecting the microphone to a certain angle.
5. Microphone position and height
When amplifying the sound, do not place the microphone close to the speaker or aim at the speaker first, otherwise it will cause howling.
The height of the microphone should be placed according to the height of the sound source. If one person speaks or several people sing, the height of the microphone should be the same as the singer's mouth; when there are many people, the microphone should be placed at an average height, and the singer should be appropriately deployed With the accompaniment and the position of the various instruments in the team, do not make the loudness too loud, light or too light, and make all the sounds within the effective angle of the microphone. If there is a lead singer or lead singer, a dedicated microphone should be placed when necessary.
When several microphones are required to be used at the same time, the parallel connection method can be adopted, but the phase problem of several microphones must be paid attention to. Only when the phases are the same can they be connected in parallel, otherwise they will interfere with each other, reducing the output and causing distortion. Microphones of different models and different impedances should not be used in parallel, because high-impedance microphones are "short-circuited" and the output voltage drops to a very low level. Under normal circumstances, microphones are used directly in parallel, and the effect is not as good as a single microphone.