Conference room microphone selection and use

As we all know, when attending a conference or giving a speech, many people have been disturbed by the occasional whistle and ambiguous sound reinforcement of a microphone. How to select a microphone and make reasonable use of it when building a conference room sound reinforcement project? ? Here's a breakdown for everyone:In the conference room, the demand for sound is usually bright, clear, and loud. When the venue was set up, the speaker could not go to the scene to audition. Therefore, if you want to reach the bright scene in the live sound, clear sound effects (loudness just right but do not whistle the demand), the microphone selection and placement method has a certain amount of knowledge.1, the selection of microphone Since different microphones have different effects on different sound sources, it is necessary to thoroughly understand the microphone's skill, function, and application before selecting the microphone. When the microphone is selected, in addition to the sensitivity of the microphone, the matching of the output impedance and the input impedance of the mixer, and the like, the directional characteristics, frequency response characteristics, and the shape of the microphone need to be taken into consideration in the conference room. In terms of directivity, the supercardioid shape is suitable for relatively long-distance pickups. The heart shape is suitable for most situations. The non-directional microphone is not suitable for speech pickup because simpleness leads to echo. In addition, in the conference room, based on the planning of the speakers, a sound reinforcement system with centralized or semi-centralized programming with suitable pointing characteristics should be selected. The directional characteristics of the microphone should be heart-shaped or super-cardioid; The system usually chooses heart-shaped microphones. If the microphone is far away from the PA speaker and the reverberation time of the hall is not too long, the non-directional microphone can also be selected. When the sound source is very close to the microphone, the skill indicator can be used to eliminate the near-talk. Near-speaking heart-shaped microphone for effects. In terms of the frequency response characteristic of the microphone, the microphone with a slightly lower static skill target and good transient characteristics is slightly better than a microphone with a slightly higher static skill target and poor transient characteristics. Two, from the low frequency to high frequency response characteristics are uniform, smooth microphone is better than a certain frequency band, the brief good, because some of the outstanding will also cause howling. In addition, dull voices are often exacerbated by excessive fire due to the microphone being too close. Of course, you can use electronic proofreading (in the sound transmission circuit) to compensate. This has no effect on the low-voice vocal sound, but there is a constraint on the front and rear movement. The distance between the caller and the microphone must be stable, otherwise the low-frequency component will have Change, and the ratio between direct sound and reverb sound (in the sound field "lively" sound field) will also change.A microphone that exhibits a large number of peaks between 6000-9000 Hz will make the accented voice become louder. Of course, proofreading can also be done electronically, but it is worth paying the dead point at the top of the peak. Therefore, the conference room usually does not need to use high-quality microphones, with a smooth and responsive microphone. As far as the internal structure type of the microphone is concerned, dynamic microphones are generally used in the conference room for sound reinforcement. Over the years, with the enlargement of the conference table, widening, most of today's condenser gooseneck microphones have been selected. In this way, when the conference table is wider, it will not be pushed to the table by the speaker and no sound can be picked up. In addition, the condenser microphone microphone head is relatively small, so as not to cover the speaker's face is also one of the reasons chosen.In summary, in addition to special requirements, meeting rooms are generally recommended for use in capacitive gooseneck heart-shaped microphones with wide frequency response, uniform frequency response transmission characteristics, smoothness, and low distortion.2, the placement of the microphone The microphone placement in the conference room is usually divided into two types: desktop placement and microphone stand placement. When placing the microphone on the desktop, pay attention to the angle and interval between the speaker's mouth and the microphone. It is better to align the middle axis of the microphone with the mouth of the speaker. At this time, the microphone output has the best frequency response characteristics; The farther the Department goes against the middle axis, the worse the frequency response characteristics and the more severe the loss of treble, and the output voltage of the microphone will also reduce the usual heart-shaped microphone. The angle between the mouth and the central axis is appropriate within the scope of 450.When speaking in the conference room, in order to enhance speech clarity, the microphone should be 20-30 centimeters away from the mouth. If it is too close, the low-frequency spout tone is easy to appear, which affects the clarity of the sound. Too far, the microphone picks up too much reflection. With reverberation, it is easy to cause howling. At this moment, if the mixing console pushes too small, the loudness will not reach the demand, and the audience will not be able to hear the content and push it too loud and easy to whistle. Therefore, it is important to accurately measure the speaker's speaking interval when placing the microphone.When more than one person speaks and multiple microphones need to be placed, the interval between the microphones should be greater than 3 times the spacing between the sound source and the microphone (ie, satisfy the 3:1 criterion) to reduce the phase interference that occurs when signals are added. phenomenon.When a person speaks and needs to pick up two or more microphones (for example, make a statement), try to keep two or more microphones as close as possible, and insist on the spacing of each microphone to the source (speaker's mouth). Keep as flat as possible to avoid phase interference when signals are added. At this moment, it is important to pay attention to the phasing of the microphones. Take two microphones as an example. If two microphones haven't picked up one microphone and the volume of the microphone is large, then the two microphones are reciprocally phased. At this moment, the phase of one microphone needs to be adjusted. Usually, the problem lies in the microphone line. Above, just adjust the wiring of one microphone. When the microphone holder is placed, since many microphone holders are triangular supports, after the microphones are installed, the center of gravity of the microphone should be placed on a certain leg. In addition, the active rod of the device microphone should not be drawn too long to prevent the center of gravity of the microphone from exceeding. The scale is dumped outside the scale.3, microphone audition Due to the particularity of the conference room, the speaker cannot be allowed to personally audition the venue (for example, the leader speaks) in most situations. Therefore, you can simply adjust the volume of the normal person and try to get the speaker’s first sentence to arrive. The volume is moderate (moderately loud and not whispering), but there is a conditioning capacity to satisfy. However, if there are many microphones, the tuner needs to perform repeated debugging between the mixer and the microphone, which is troublesome and the power is not high.That is, put the microphone in the future, put all the microphone's mixer faders at the lowest, the gain knob at the minimum, and then put the amplifier in the proper direction of the usual use, push the mixer's main output to 0 dB. , Then push the corresponding fader of a certain microphone to the highest level of the road (usually the mixer is 10 ~ 12 dB), then slowly adjust the gain knob of the microphone on the mixer, and carefully monitor the sound, Until you hear a slight whistling sound, move the knob back 3 dB, and then pull the fader back to 0 dB. In this way, the way the microphone can not only ensure that the speaker has a loud volume of loudness, but does not lead to howling, when the speaker sounds smaller, there is a margin of satisfaction (13 dB) for adjustment. Same as other microphones. In this way, adjusting the future and opening multiple microphones together will not cause howling.