At present domestic dance halls used by professional audio, mostly imported equipment, it should be said that the reliability is higher. The main problem is the operator specialized quality not neat, really very few units equipped with qualified tuner. So, often appear the poor acoustics caused by improper operation, even result in equipment damage. This article in view of the medium and small halls in audio equipment operating point with explanation, can be as reference to make the operation procedures. In addition, in small and medium sized ballroom caused by sound microphone feedback self-excited squealing phenomenon, the users are common headaches, often occurs because the noise will make guests, acoustics, severe cases can cause equipment damage. Self-excited squealing phenomenon, therefore, is an important problem in ballroom audio use, the following described respectively.
A, audio equipment, shutdown sequence
Should boot in by the former to the later order, that is, by the audio equipment (CD machine, LD, DVD player, tape recorder, video recorder), audio processing equipment (pressure limit, exciter, effect, frequency divider, equalizer, etc) to audio power amplifier to televisions, projectors, monitor. When shutdown sequence on the contrary, should first turn off the power amplifier. This operation can prevent open and shut down the impact on the equipment, prevent burning power amplifier and speakers.
Second, the preparation, debugging before singing
1. The volume control potentiometer position shall be transferred to the largest of the power amplifier; Tuning stage accompaniment music and shunt pusher microphone should be placed in 0 db; Tuning stage GAIN the input GAIN distribution in modulated good position; Mixer minimum volume pusher in first place (bottom); Mixer quality compensation button are in the middle position.
2. Test the accompaniment channel, that is to say, with CDS or LD pan song music, the mixer urgent he jump completed Man jams soil, near to - 6 db, singing and accompaniment music at this time is roughly the volume of the normal work. But should pay attention to the volume to moderate sweet, loudness too easy to make the person fatigue and unbearable. Soundman and should to the hall to listen to different sites in effect. Such as stereo audio and video, music, sound, etc. Put the pieces should be from already familiar tune, volume can be adjusted repeatedly (adjustable shunt GAIN GAIN) and shunt timbre compensation, until the sound happy. The requirement to the effect of music should be powerful, have aesthetic feeling, high-pitched not harsh, bass can't cloudy, voice clear, such as dental clearly audible voice. But not too much. Shunt pusher at 0 db, the total volume pusher at 0 db, adjust the shunt GAIN input GAIN button makes the AU table indicating 0 db, the system achieve the rated output power. But normal work, the total volume is so - a callback below - 6 db or - 10 db, less than the rated power output.
3. The test receiver channel. In general, to prepare at least two receiver channel. Try microphone sensitivity and dynamic performance, and then add reverb singing and accompaniment music, song through reverb processing, should be better than the original singing sound more round, round and have layers, rich presence. Microphone volume adjustment: shunt pusher at 0 db, microphone volume adjustment of shunt GAIN input GAIN button, occasionally shunt peak level indicator light shining as well, the total output power measurement by AU table instructions.
4. Adjust small band for audition, namely to carry all kinds of musical instrument microphone sound and electrical signals for audition, according to proportionally balanced stereo music style.
5. The adjustment of the video image, namely, the projector and TV should be by adjusting the brightness, contrast and color saturation knob to make the image clear and colorful. Audio player should be able to skillfully use DVD and eventful, familiar with and so the plate on the list. Pay attention to while singing in A formal, should press DVD on D/A. The original singer singing off.
Third, the adjustment of the audio processing equipment
1. The room equalizer. Room equalizer has two effects, one is to adjust the sound quality, make up the hall reverberation time frequency response caused by the imbalance; Another important role is down a certain frequencies, inhibit whistlers caused by acoustic feedback. Room equalizer that should maintain a sound engineering commissioning at ordinary times sort of fixed position.
2. Pressure limiting device. In sound engineering medium voltage limit device is important equipment, its role: one is dynamic range compression or restrict programs, prevent overload or distortion, the power amplifier and speaker protective; Another important role is to improve the program loudness (this can be clearly felt by ear). Pressure limiting device adjustment data is as follows: (1) the noise GATE door: indicator noise when the door is shut, small voice. Noise effect. Landing when the input signal to the threshold electric started off at ordinary times, noise door generally between 0 pen to - 20 db. (2) the compression THRESHOLD level THRESHOLD: decided to start the compression level, general at - 10 to 0 dB, began to compression GAIN decreases, and GAIN REDUOTION (dB) indicator started on. RATT0: compression ratio in a 2:1; Action time ATTACK: in 10 ms; RELEASE time RELEASE: in o. 3 s.
3. The reverb units. The current widely used digital reverb units. This kind of machine internal curing many different reverberation effects to choose from. Soundman and cope with the reverb units used by various reverberation effect each demo audition, can use the program, when the tuning can be used with machine keyboard out at any time.
Four, the key points of the tuning (mainly operating mixer)
1. In the control room, karaoke bars tuned staff tuning up listening to monitor should be used when the speaker and listening to the headphones, respectively, to monitor and return in the main channel. Soundman relationship should be familiar with listening to the sound and the sound, sound quality adjustment to a large extent rely on personal hearing.
2. Use the pressure limit and actuator in order to increase the loudness of sound and beauty. The adjustment of the exciter mainly by hearing, should press equipment operating instructions will be a tuning plump musical sound.
3. With a reverberation beautify the song. For non-professional singers should be the appropriate increase reverberation, to cover up the flaws in noise and sound.
4. Low frequency and high frequency volume hours notice to ascend; Appropriate intermediate frequency, when the volume to increase the brightness of sound.
5. The tuning is given priority to with singing. When the song before, accompanied down down gradually, the song is highlighted. Low frequency should be 3 to 5 db attenuation, high frequency attenuation 3 db, should be more than 7 KHZ, ascension can be near the low frequency 200 hz, 2, 4 KHZ ascension 3-6 db can obviously feel the song bright. To the disco or rock 'n' roll is to pay attention to improve significantly low frequency (40-100 hz) and high frequency (7-20 KHZ).
6. Improve the bass must not fierce knob screw compensation, in order to avoid damage due to excessive power output power amplifier and speakers. The same is true of low frequency regulation requirements of equalizer.
7. If there is a sound feedback whistlers, total volume should be quick to call the sound Taiwan pusher drop-down to remove whistlers, find out the reason and then push on step by step.
8. Main failure can't send out, but will return to listen to the speaker the rotation Angle of temporary instead of main channel, to continue to sing. For singing with a microphone, should have a backup, backup when silent phone can be used. DVD also should have a backup, backup when DVD failure can be used.
Five, the acoustic feedback inhibition (whistlers)
1. The microphone sound feedback cause self-excited whistlers is the common phenomenon of karaoke bars and kara 0 k hall, due to acoustic feedback, generally cannot gain amplification system. Acoustic feedback noise reason is: (1) receiver is apart from the speakers too close, microphone is pointing to the speakers; (2) tuning stage reverberation adjustment is too large; (3) the microphone volume is too large; (4) not connected pressure limit; (5) hall acoustics design flaws.
2. In view of the above reasons can take the following measures:
(1) the stage for the singer's activities limit the scope of a general, whistlers should not happen in this scope. That is to say, the singer should not be too close to the main speakers, the main speaker should be symmetrical in the wings; The singer's stance should not make the microphone is pointing to the speakers.
(2) the stage in karaoke bars should be acoustic processing, metope should be installed on both sides and sound-absorbing material.
(3) through pressure limit, the compression ratio should be set to < = 2:1, the action time of 10 ms, release time is 0.3 s.
(4) tuning stage of reverberation and don't drive too large volume adjustment.
(5) the above measures can not work, can adjust the equalizer, frequency of easy to produce the noise attenuation. Specific operation method is as follows: the equalizer to recorded each frequency point location; Then, the demonstration. Increase the volume (with mixer total pusher adjust), to the system just produce self-excited position, the adjusting knob on the equalizer from low frequency began to cut them one by one, can effectively eliminate self-excited the noise frequency point, according to the experience in general only a self-excited resonant frequency (250 hz), the drop-down 3-5 db near the frequency, the frequency point should still keep the position of the original record. This method can effectively suppress acoustic feedback, but not both music effect. By adjusting the amplification gain has 5-6 db stability margin, it is necessary for system stability.
(6) if these measures are still unable to work, can consider to install acoustic feedback suppressor, for example, frequency shift device can effectively overcome the acoustic feedback, give the amplification gain 5-6 stability margin on them