What Is Feedback?

• Feedback is a sound loop that occurs when a microphone plays through a sound system, picks up the sound of its own amplification and then amplifies this sound, resulting in an uncontrolled noise emitting from the speakers. Unless you reduce the microphone's volume level, the mike will pick up the sound of its own feedback and amplify it again and again. This can destroy an overloaded sound system.
  
  

Monitor Placement

• Monitor speakers, which are used to give performers an onstage mix of their live sound, usually should be positioned in front of the vocalist's microphone stand. This ensures that the singer can hear the monitor output well and it faces the monitor away from the crowd. Most importantly, the microphone is facing away from the monitor.
  
  

Microphone Position

• Most vocal microphones are geared to accept sound sources from directly in front of them and a little to either side, but not at their rear. Therefore, angling a vocal mike directly away from the monitor is normally the best way to minimize the risk of feedback. Any other onstage sound sources, such as amplifier microphones, should also point away from the monitors as much as possible.
  
  

Supercardioid Microphones

• Although most vocal mikes have a "pickup pattern" that rejects sound from the rear, supercardioid microphones do pick up sound produced directly behind them. An example is the Shure Beta 58A, which is designed not to amplify sound generated to its sides. If you are working with a directional microphone such as this, make sure that the monitor speaker is not positioned directly behind it. Angle the monitor slightly to one side so that it is still facing the singer, but not in the line of your supercardioid mike's pickup pattern.