Choosing the right microphone is becoming more and more difficult. There are more and more types of microphones, each with its own strengths and excellent quality. Therefore, in addition to the price, the biggest influencing factor when purchasing is personal preference. Below we will introduce the reference elements for reasonable purchase of microphones.
①First of all, of course, the smoothest response
When choosing a microphone, the user should be the first to care about its frequency response characteristics. The frequency response must be wide enough to pick up the entire range of sounds, so that the quality of natural sound sources does not change audibly.
②The electrical output impedance is very important
Because it should match the input impedance of the mixer, tape recorder or amplifier. The impedance unit is Ω, usually at a frequency of 1kHz. The typical impedance of a dynamic microphone is 150Ω, 200Ω, or 300Ω. As a rule of thumb, the input impedance of the device should be at least 3 times the microphone impedance. All mixers currently on the market meet this requirement.
In addition, there are high-impedance microphones and dual-impedance microphones that can switch between low and high impedance. The length of the cable connected to the high-impedance microphone should not exceed 7m, because the cable capacitance will cause high-frequency attenuation.
The microphone with built-in amplifier can be inserted into any load higher than or equal to the minimum load impedance. If the microphone is connected to an input with a load lower than the minimum load impedance, the frequency response will be impaired.
Proximity effect is the effect of using near-transmission technology to boost bass, that is, the microphone is placed a few centimeters away from the sound source. Although in some situations this effect can produce a strong and full sound that some singers like, there are many situations where bass boost must be controlled or avoided altogether, for example, when recording a conversation. The proximity effect may make the conversation incomprehensible. Some microphones are equipped with a bass filter to compensate for the proximity effect, which can be used in home recording to avoid low-frequency noise from electrical appliances such as solar tube transformers, refrigerators, and air conditioners.
④Select the directivity of the microphone
Among all kinds of microphones at the same price, omnidirectional microphones usually have the broadest and smoothest response, and are also less sensitive to wheezing, hand-held noise, and wind. If there is no too much external noise or too much reverberation, they are very suitable for most applications. For example, dynamic omnidirectional interview microphones are widely used among reporters.
Although omnidirectional microphones accept sound waves from all directions well, some users may prefer to accept sound waves from one (one-way) or two (two-way, figure-eight) directions. This means that in order to obtain the same ratio of direct sound to reverberant sound, the distances between the cardioid and bidirectional microphones, supercardioid microphones and sharp cardioid microphones from the sound source are respectively 1.7 times the distance between the omnidirectional microphone and the sound source. 1.9 times and 2 times. For example, conference microphones can pick up sound sources from a long distance, and capacitive interview microphones can also obtain clear target sounds at a long distance, and are usually used for simultaneous recording of large-scale performances.
⑤ Overload sound pressure is mainly important for condenser microphones
Condenser microphones work in a linear state up to a certain sound pressure level (SPL). This SPL is called overload or maximum SPL, and the frequency is usually 1kHz. If the sound pressure exceeds this value, the output signal will deteriorate due to harmonic distortion.
At the maximum SPL, the total harmonic distortion coefficient should not exceed 0.5% or 1%. It is impossible to overload dynamic microphones in normal applications, and they will never actually distort the signal.
Sensitivity is the microphone output voltage under a certain SPL. It is generally measured at 1kHz and the unit is V/Pa or dBV. At a certain gain setting, the more sensitive microphone produces louder sound, but the user should use it carefully at this time, because the risk of feedback also increases proportionally.