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Microphones, Monitors and Feedback

Excellence in the Arts - by - October 24, 2008 - 02:11 Etc/GMT+5 - Be first to Comment!

A few general guidelines and recommendations about stage monitors, IEM and feedback.

  • The more sound that is generated on the platform, the more the house audio system has to be turned up to “overcome” the volume of the stage, otherwise the sound off the platform sounds “muddy” or muffled in the house and the house audio technician has a hard time balancing the mix if they don’t have control of as much of the sound as possible. This is in part from sound on the stage coming out into the congregation, but also is caused by microphones on the stage picking up extra sound on stage besides what they are suppose to be picking up. Remember the microphone is the ear to the sound system, and is going to hear what ever sound is at it’s location. If you can put you ears where a vocal mic goes and hear a lot of instruments and amplified sound in addition to the voice, the mic will pick these up and amplify them thru the sound system, loosing the ability to have clean vocals and individual control over each audio source. So in general the goal is to keep the stage audio level as low as possible to avoid these two problems.
  • IEM systems are great for lowering the stage volume because they allow the vocalist or musician to hear what they need to hear without the microphone “hearing” those sounds – BUT – the musician can only hear what they need to IF those things are going thru the audio system and monitor system. The most common complaint with IEM systems are that the artist feels disconnected from the congregation or from what is going on around them that might not be mic’ed. The solutions to these problems are two fold. First, microphones need to be put on everything that needs to be heard, in some cases this included the congregation, and second, the artist needs to be able to control they mix so they can balance what they hear appropriately. This control is the purpose of the Aviom musician mixer system.
  • Feedback. No one wants it, but very few people understand what causes it so they can help avoid it. Feedback is caused when the sound the microphone is picking up is amplified by the sound system, and this amplified sound reaches the microphone at a louder level than the original sound. This louder sound is then amplified again and again, causing a “loop” which quickly turns into a very loud squeal. So how to avoid feedback? Make sure the original sound going into a microphone is louder than the amplified sound coming from the speaker back to the microphone. Several things can influence this, but in general:
  1. Keep the microphone as close as possible to the sound source. The closer the mic is, the louder it picks up the sound. For instance, with a voice, a lapel mic is ~8-10” away from the mouth. A handheld mic is typically held 3-5” away from the mouth. A headset mic is typically only 1” away from the mouth. A lapel mic is a lot more likely to feedback when trying to turn it up to the same level you use a handheld or a headset mic. Likewise, a headset mic typically is as loud as a very close held handheld mic and has a lot lower risk of feedback.
  2. Keep the speakers as far away from the microphones as possible. This is typically done partially thru using direction speakers and directional microphones where the speaker is projecting the sound one direction, and the microphone is picking up sound from the opposite direction. This is also accomplished using the acoustics of the room to control what sound reflects back to the stage.
  3. Use as high quality speakers and microphones as possible. Higher quality speakers and microphones have smoother pickup and response patterns, with less peak frequencies that are louder and more prone to feedback.

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