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 of selection. For example, high-quality recording and broadcasting mainly require good sound quality. Condenser microphones, ribbon microphones or advanced dynamic microphones should be used; for general sound reinforcement, ordinary dynamic coils can be used; when the speaker moves or speaks The distance between the microphone and the loudspeaker is relatively large, 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 equipment is generally 48V phantom power supply.
Impedance matching
When using a microphone, the output impedance of the microphone and the input impedance of the amplifier are the same as the best 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 impedance of 150Ω, although the output can increase by 7Db, the high and low frequency sounds will suffer significant loss.
Connection 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 dual-core glued 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 cable of low impedance microphone can be extended to 30m~50m.
Working distance and proximity effect
Generally, the 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. 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.
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.
Microphone position and height
When doing sound reinforcement, do not approach the speaker or aim the microphone at the speaker first, otherwise it will cause howling. The height of the microphone is determined 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 singers and singers should be appropriately deployed. The position of the accompanist and the various instruments in the team should not be too loud or too light, and all sounds must be within the effective angle of the microphone. If there is a lead singer or lead singer, a dedicated microphone should be placed when necessary.
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