As everyone knows, when attending a conference or giving a speech, many people have been disturbed by the occasional whistling of the microphone and the ambiguous sound reinforcement. How to choose the microphone and make reasonable use when constructing the conference room sound reinforcement project What? Here is a breakdown for everyone:
In the conference room, the sound is usually bright and clear, and the loudness should be moderate. When placing the venue, the speaker cannot go to the live audition. Therefore, in order to reach the bright and clear sound when the sound is on the scene (the loudness is just right but not the need to whistle), the method of selecting and placing the microphone has certain knowledge.
1. The selection of the microphone Because the different microphones have different effects on different sound sources, it is necessary to have a deep understanding of the microphone's skill characteristics, functions, and applications before selecting the microphone. In addition to the electro-acoustic indicators such as the sensitivity of the microphone, the matching of the output impedance and the input impedance of the mixer, the microphone should also be considered in the conference room, such as the directional characteristics of the microphone, the frequency response characteristics and the shape of the microphone.
In terms of directivity, the supercardioid shape is suitable for long-distance interval pickup, and the heart shape is suitable for most cases. The non-directional microphone is not suitable for speech pickup, because simple will lead to echo. In addition, in the conference room, according to the planning of the speaker, to select the microphone with the right characteristics. For centralized or semi-centralized sound reinforcement systems, the directional characteristics of the microphone should be heart-shaped or super-cardioid; for a diffuse-planned sound reinforcement system, a heart-shaped microphone should usually be selected, if the microphone is far from the sound reinforcement box, The reverberation time of the hall is not too long, and the non-directional microphone can also be selected. When the sound source is very close to the microphone, the heartbeat microphone can be used to eliminate the near-talk effect.
In terms of the frequency response characteristics of the microphone, microphones with a slightly lower static skill target and better transient characteristics are better than those with a slightly higher static target and poor transient characteristics. Two, from the low frequency to the high frequency frequency response characteristics of the uniform, smooth microphone is better than a certain band is outstanding, because some of the outstanding will also cause howling.
In addition, blunt voices are often exacerbated by excessive fire due to the microphone being too close. Of course, it can be compensated by electronic proofreading (in the sound circuit), which has no effect on the sound of the audio too low, but there is a constraint on the movement before and after, the interval between the speaker and the microphone must be stable, otherwise the low frequency component will be Change, and the ratio between the direct sound and the reverb sound (in the "live" sound field of the acoustic condition) will also change.
A microphone with a large number of peaks between 6000 and 9000 Hz will make the accent with arpeggio become heavier. Of course, you can also use the electronic method to proofread, but pay the value of bringing dead spots on the peak. Therefore, it is not necessary for a conference room to use a high-quality microphone, and a microphone with a smooth response can be used. As far as the internal structure type of the microphone is concerned, in general, the conference room sound reinforcement has previously used a dynamic microphone. Over the years, with the increase and widening of conference tables, most of them have chosen condenser gooseneck microphones. In this way, when the conference table is relatively wide, it will not be pushed to the table by the speaker and no sound can be picked up. In addition, the condenser microphone has a small microphone head, and it is one of the reasons why the speaker's face is not covered.
In summary, in addition to special needs, the conference room usually recommends a capacitive gooseneck heart-shaped microphone with a wide frequency response, uniform frequency response, smoothness and low distortion.
2, the microphone placement of the conference room microphone is usually divided into desktop placement and microphone stand placement. When placing the microphone on the table, pay attention to the angle and spacing between the speaker's mouth and the microphone. It is best to align the microphone's center axis with the speaker's mouth. At this time, the microphone output has the best frequency response characteristics. The farther the department violates the intermediate axis, the worse the frequency response characteristics, the more severe the treble loss, and the output voltage of the microphone will also be reduced. Usually a cardioid microphone, the angle between the mouth and the central axis is suitably within 450 scale.
When speaking in the conference room, in order to enhance the clarity of speech, the microphone should be 20-30cm from the mouth. If it is too close, it will be easy to present low-frequency jets, affecting the clarity of the sound. Too far, the microphone picks up too much reflection and Reverberation sounds can easily lead to howling. At this moment, if the mixer is pushed too small, the loudness of the sound will not reach the demand, and the audience will not be able to hear the content, and it will be too big and easy to scream. Therefore, it is important to accurately estimate the speaker's speaking interval when placing the microphone.
When there are many people talking, you need to place multiple microphones, so that the interval between the microphones is greater than 3 times the interval between the sound source and the microphone (that is, the 3:1 criterion is satisfied) to reduce the phase interference that occurs when the signals are added. phenomenon.
When a person speaks and needs to use two or more microphones to pick up the sound (for example, make a statement), place two or more microphones as close as possible, and stick the interval between each microphone and the sound source (speaker's mouth). Try to be flat to avoid phase interference when the signals are added. At this moment, it is important to pay attention to the microphone phase to be common. Taking two microphones as an example, if two microphones do not have a microphone and the volume is large, then the two microphones are reversed. At this moment, the phase of one microphone needs to be adjusted. Generally speaking, the problem lies in the microphone line. On, just adjust the wiring of a microphone. When the microphone holder is placed, since many microphone holders are triangular brackets, after the microphone is installed, the center of gravity of the microphone should be projected on one of the legs. In addition, the movable rod of the device microphone should not be drawn too long to avoid the microphone center of gravity exceeding The stent is dumped outside the scale.
3, the audition of the microphone due to the special nature of the conference room, in most cases can not let the speaker come to the venue to audition (such as leadership speech), so just adjust the volume of the normal person, try to make the speaker The first sentence is moderate (the sound is moderate and not whistling), but there must be a satisfactory conditioning capacity. However, if there are many microphones, the tuner needs to perform repeated debugging between the mixer and the microphone, which is very laborious and powerless.
That is, the microphone is placed in the future, the mixer fader of all the microphones is placed at the lowest position, the gain knob is adjusted to the minimum position, and then the power amplifier is adjusted to the proper orientation to be used, and the main output of the mixer is pushed to 0 dB. Then push the corresponding fader of a certain microphone to the highest level of the road (usually 10~12dB for the mixer), then slowly adjust the gain knob of the microphone on the mixer, and carefully monitor the sound until listening When there is a slight whistling sound, turn the knob back 3dB, and then pull the fader back to 0dB. In this way, the microphone can ensure that the speaker has a satisfactory volume loudness, and does not cause howling, and when the speaker sounds small, there is a margin (13dB) that can be adjusted. The same can be done for other microphones. In this way, if you turn over multiple microphones together, it will not cause howling.
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