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How to allocate microphones reasonably

Author:admin   AddTime:2021-07-02

In recent years, with the continuous improvement of professional stage equipment and related technology, various forms of cultural performances have become more abundant and comprehensive. There is also an increasing demand for the number and types of microphones in various activities. Including many non-professional performances, the requirements for stage art, lighting, sound, and video are also very high. While satisfying people's growing spiritual civilization, it also brings new opportunities and challenges to the performance audio industry. In fact, regardless of whether the activity is professional or amateur, a sufficient number of microphones is a strong guarantee for sound quality and on-site stability. But it is not that the more microphones, the better the sound and the higher the safety. From the perspective of sound pickup, there is no need to use multiple microphones for a sound source that can be fully picked up by one microphone. In addition to increasing the workload of the corresponding tuning, unnecessary interference and crosstalk may also be formed, and poor control will be counterproductive. From a safety perspective, every additional microphone adds a hidden danger of noise. Such as the poor contact of the connector wires, the frequency cut-off and string frequency of the wireless system, and so on. In addition, there are too many channels used by the console, resulting in frequent page turning, and there are also safety hazards such as misoperation and slow system response. In addition to the increase in material resources, manpower, energy, and time must be increased accordingly. Therefore, even if the hardware conditions are sufficient and there is too much demand for microphones, it is necessary for us to appropriately reduce the overall number of microphones through safe and reasonable design. Due to my work, the author often comes into contact with activities that use a lot of microphones, and has accumulated a little experience. I would like to share with you here. I hope to bring some help to those who are not involved in the world in their work.

Microphone, also known as microphone, is a kind of electro-acoustic equipment, which belongs to microphone. It is a transducer that converts sound to electricity. It generates voltage on electro-acoustic components through sound waves, and then converts it into electrical energy. Used in a variety of loudspeaker equipment. There are many types of microphones and simple circuits. Analyzing the microphone circuit mainly grasps two points: signal transmission loop analysis, which is relatively simple, and analyzes various microphone input jack circuits. Microphone signal amplifier analysis, the microphone amplifier is a small signal low-noise audio amplifier, it is not difficult to analyze the microphone level control circuit.

A balanced wire consists of two wires and a shielded wire; in an unbalanced wire, there is only one wire, and the second wire is replaced by a shielded wire. The advantage of the balanced line is that the two wires of the line have the same strength of the unwanted noise signal, so the two can cancel each other out. The unbalanced line transmits the noise signal to the next stage of the line. If the audio signal is strong or the unbalanced line is short, no noise may be heard. But the microphone cable is generally very long. Think about it, we pulled the cable from the recording room, passed the sound box through the wall, and then entered the control room's tuning and recording system. Therefore, we have to use a balanced cable, and use a balanced plug accordingly: XLR, commonly known as Canon head or male and female head; or TRS with large three-pin cores.

The working principle of the wireless microphone circuit

The sound is coupled to the base of the triode through the microphone through the high and low frequency resistance-capacitance filters composed of R1, C1; R2, C2. Due to the positive feedback amplification of the triode, the high-frequency signal of the high-frequency oscillator formed by L1 and C3 is equivalently fed back to the base of the triode via C4. The two signals are mixed by the triode to form a high-frequency FM carrier (88~108MHz), which is transmitted to the antenna via C6, and the FM signal is transmitted from the antenna to the surrounding space.

First of all, I want to emphasize that the experience I’ve shared for you is applicable to comprehensive performing arts activities with rich and varied performances. The so-called reduced quantity means that some microphones and channels are repeated in different programs under the premise of ensuring sound quality. Use, thereby reducing the overall quantity. For specific programs, in order to accurately restore the sound details, sometimes a microphone is specially added. For example, keyboard instruments, the high and low frequencies should be picked up separately. For repertoires such as traditional concerts, complete dramas, and operas, the content format is relatively fixed, and the microphone configuration must meet the needs of the band's organization and plot, and there is generally not much room for reduction. In addition, the microphone scheduling described in this article mainly refers to various types of wireless microphones that are suitable for flexible switching. According to the transmitter classification, there are three main types of wireless microphones commonly used in stage performances. 1. Hand-held transmitter: cylindrical handle transmitter, equipped with detachable or integrated, moving coil and capacitive pickup. Generally, the sensitivity is low, and the directivity is cardioid or super cardioid, and most of them have been processed with corresponding low-frequency attenuation and blowout prevention, which is suitable for close-talking use of human voice. It can also be installed on a stand for instruments that are suitable for near pickup and low-frequency response. Convenient and flexible, but not suitable for long-distance pickup or use for bass instruments; 2. Bodypack transmitter: generally a square transmitter the size of a cigarette case, suitable for hiding in most clothing. It can also be fixed on many musical instruments or props with external forces such as tape. Connect miniature pickup heads such as lapel clips or headsets through short wires. Most of them are electret or capacitive, and the directivity is mostly omnidirectional or cardioid. Lavalier clips usually have relatively high sensitivity and are suitable for mid-to-near (approximately 8-20CM) distance pickup, or for picking up sound sources with weaker sound pressure at close distances. The sensitivity of the headset is relatively low, which is suitable for near and ultra-close (about 2-12CM) distance pickup of human voices and some musical instruments. Both types of pickups have good concealment, but generally have poor low-frequency response. Affected by the structure, the speed of wearing and installation is relatively slow; 3. In-line transmitter (commonly known as "grenade"), a small transmitter with a volume equivalent to a waist pack. Concealment is also comparable to a waist bag. It comes with a XLR socket, which can be directly plugged into any wired microphone with XLR head, and can also be connected to a miniature microphone through an optional or customized adapter. The indicators related to the sound and the way of picking up the sound completely depend on the connected microphone.

When we accept a comprehensive evening party with richer performances, we should first communicate with the director group and performers to learn more about the specific formats of different programs, and draw up initial plans for the type and number of microphones. Under normal circumstances, sound sources that do not need to be temporarily moved, such as fixed bands and chorus behind the stage or side of the stage, are recommended to be picked up by wired capacitors and dynamic microphones. One is that the wired microphone is relatively stable and has higher security; the other is that it can reduce the burden of the wireless system and avoid hidden dangers such as cross-frequency. Relatively fixed programs such as instrumental music and chorus need to be moved quickly. It is recommended to use a direct plug-in "grenade" with corresponding wired microphones, which can meet the requirements of sound quality and flexibility at the same time. "Grenade" is also suitable for playing and singing programs. If conditions permit, it is best to pick up musical instruments and vocals separately. For example, a "grenade" with a stand for musical instruments is equipped with a condenser microphone, and a handheld or head-mounted microphone with a stand for vocals. If it is a combination of singing and playing with more performers, it can also be handled in the form of a small chorus, that is, use several condenser microphones with "grenade" to evenly pick it up. The ratio of musical instruments and vocals is balanced by the position of the microphone. Singers, hosts, etc. try to use handheld wireless microphones specially designed for vocals. Some instruments that are suitable for near pickup and have low requirements for low-frequency response can also be picked up with a handheld microphone fixed on the stand. Programs with action performances, such as sitcoms, operas, sketches, etc., naturally use miniature microphones such as wireless headsets or lavaliers. If you have a choice, head-mounted microphones should be the first choice. Because the pickup distance is close and the direction is easy to control, it will get higher transmission gain and better frequency response than lavalier microphones. The skin-colored lavalier microphone can also be fixed on the actor's head to pick up the sound, such as tape on the forehead or cheek. Due to the relatively high sensitivity of the collar chuck, it should not be placed too close to the mouth to avoid clipping distortion or spray microphones.

The above are the common pickup methods for some common performance forms. Through communication and understanding, we can draw up the type and number of microphones needed. Then, according to the sequence of the program, a specific sound pickup plan is formulated. Most directors rarely consider sound pickup when selecting programs and ranking. Due to the variety of variety shows, the variety of programs is rich and varied, and the relocation and connection have become a very important link. It is the key design and rehearsal in the synthesis of the stage. The allocation and scheduling of microphones is also an important part of it. It is inevitable to go up and down the microphone when relocating. Experienced directors will win the time for setting up and dismissing in the dark by means of program scheduling, hosting or video connection, scene switching, lighting changes, etc., and reduce and dilute the time Relocation link. The sound engineer can also use the above measures to put forward reasonable suggestions to the director team according to the specific situation of the department. Of course, the sound engineer can arbitrarily adjust the sound pickup method under the premise of not affecting the program and the visual effect. Usually the sound personnel are exposed to the top and bottom of the microphone in the audience's line of sight, which can be called Mingshang. On the contrary, it is dark. In fact, in addition to some need to use a microphone stand, and it is not convenient to use the above methods, most of the transfers can be done in secret except for the upper and lower links. The most effective thing is to set up the microphones in advance and let the actors directly bring them on stage. This is definitely the way most directors are more willing to accept, and it can also avoid the impact on the pickup effect due to the deviation of the pole microphone direction and position. Various miniature wireless microphones are very suitable for all kinds of vocal instrumental performances that are temporarily up and down and suitable for close pickup. For example, DPA’s 4099 is equipped with a dedicated card holder for many musical instruments. The XLR adapter can be used to directly plug into the "grenade", and the optional bodypack adapter can be connected to the corresponding bodypack transmitter. It is a better choice for close pickup of musical instruments. . It is also very practical to remove the ear hook part of the headset microphone and attach the pickup head with a short rod to the instrument. Both of these methods can maintain a distance of 5-10 cm from the sound source, which can effectively reduce the distortion that is easily generated by ultra-close pickup, and can also appropriately reduce the probability of accidentally touching the pickup head. If only lavalier microphones are available, you must be cautious, because the maximum sound pressure of the lavalier pickup head is relatively low, and it is not convenient to control the distance to the sounding body, so it is not suitable for picking up high sound pressure at close range Sound source. Of course, some soft touch physical means can also be used to keep it away from the sounding body. Whether it is a headset, a lavalier or a special sticker for musical instruments, installation and replacement will take a certain amount of time. In order to ensure the accuracy of the position and pointing, it is often fixed with the help of external forces such as tape, so it is difficult to achieve sharing between adjacent programs (for example, using the time of the announcement and the intro, replacing the headset microphone). However, if different miniature microphone heads are fixed to the corresponding pickup object in advance, only replacing the transmitter will save time. The miniature microphone head of the same interface can be replaced as long as it is unplugged and plugged on the belt bag. The small transmitter can also be quickly placed in a suitable location, such as in a pocket or inserted in the waist. Basically, there are a few host words or a few preludes to complete a change. The premise is that the microphone head required for the next program must be fixed in advance. In addition, when plugging or unplugging the connector, it must be in a mute or power-off state. For the flexibility of use, the author adheres to the principle of multiple uses when purchasing a wireless system. There are 40 channels for wireless reception in my office, but 60 channels for transmission. Handheld, grenade, and waist pack have 20 channels each. The frequencies are all in the same range, which is convenient for replacement and sharing. The miniature microphones are mainly worn on the head. In this way, the cost is lower than 60 independent wireless systems, but the flexibility of alternate use is far greater than 40 channels. In order to increase the number of temporary channels, the two transmitters can also be tuned to the same frequency. For example, in a program with a large bodypack usage, it can be temporarily occupied, and the frequency of the hand-held transmitter that is idle at that time is temporarily turned off. It must be noted that when two transmitters with the same frequency are used, only one of them can be turned on.

These measures can indeed effectively expand the number of temporary channels. After reasonable alternate scheduling, the total number of actual channels can be greatly reduced. However, if the design is not rigorous and the implementation is not standardized, there will also be great security risks. Therefore, it is necessary to consider comprehensively when designing the plan, leave a margin for the time and number of microphones alternate, the main microphone should be backed up, and try to minimize the sharing of channels between adjacent programs. The above-mentioned methods such as plugging and unplugging transmitters and sharing frequencies, although I often use them, are really helpless. A savvy and rigorous professional team must be used to implement them, otherwise it will be difficult to ensure safety. Another important prerequisite is that a digital mixer must be used. The scene can be stored and recalled conveniently, so that the changeable form of the program can always maintain the basic state of the tuning. Multiple assignments of control groups (VCA or DCA) can usually be stored and recalled along with the scene. So this function is very practical when it is inconvenient to turn pages. Nevertheless, the channel planning still needs to be carefully designed, especially when it comes to mixers whose pushers cannot be fully customized. Those important and frequently adjusted channels should be placed as conspicuously and easily as possible, such as the two ends of the entire area. If conditions permit, using different colors to distinguish important channels is also an effective measure to reduce misoperation. Because the control group can only control the level centrally, the channels that can adjust the parameters of equalization and compression at any time need to be handled separately. It is best to place these important channels and the faders that control the grouping on the same page. This is easier to implement on a mixer where several areas can be paged separately. The allocation of putters should be emphatically considered, and page turning should be minimized in the same scene. In order to put together on the same page, the same channel can also be allocated repeatedly on different pages. Those microphone channels that are repeatedly used in different programs generally have a large adjustment range. Make sure in advance when switching scenes. Once you adjust the wrong scene, it is difficult to remedy it. Therefore, when the author stores scenes, the last step is to mute all the sounds. When the current program ends, switch to the next scene quickly, and then manually cancel the mute after confirming that it is correct (the mute grouping function can be used). Although there are two more actions, it can add a guarantee of safety.

Of course, there are many less common or unique and innovative performances. The scheme of microphone pick-up and configuration also needs to be continuously explored. There is no need to follow the rules for conventional pickup methods. The key is to see whether the pickup characteristics of the microphone are consistent with the sound characteristics of the sound source in the corresponding program. In fact, although various microphones have different sound characteristics, they have a wide range of adaptations. Some differences in parameters can be compensated by the adjustment of subsequent equipment. For example, through the adjustment of equalization and level, two different types of microphones can be very similar when picking up certain sound sources. Therefore, the sound pickup scheme can also be flexibly processed through experiments as needed. In short, the reasonable allocation and scheduling of microphones requires long-term accumulation of experience and meticulous design and implementation. On the premise of ensuring sound effects and safety and reliability, by making full use of professional equipment, effectively reducing the number of microphones and channels, not only can save limited resources, but also play an important role in ensuring the smooth progress of the entire event. .

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