In part one we looked at how your microphone can impact feedback on stage. Now we look at how to setup your PA system and examine some gear that can eliminate feedback on stage.
PART 2: YOUR PA SYSTEM
Setting up your PA System
As well as using your microphone correctly, the way you set up your PA system can also make a great difference to problems caused by feedback on stage. First, as feedback is more likely to occur at higher volume levels, ask yourself how loud you really need to be. Playing with a little less volume will help reduce the potential for feedback and may also help avoid damaging your (and your audience’s) hearing in the process. In most situations you will need to make sure you set up your PA speakers in front of your microphone, however there are a few systems that use line-array technology (such as the LD Maui or Bose L1) that can be used behind the microphone at medium volumes if needed. If your system has a separate subwoofer, you should also try (within reason) to move this as far away from your vocal microphone as possible.
Positioning Your Monitor Speakers
Different microphones behave in different ways and it is always best to check in their documentation where your mic is least sensitive in order to know the best place to position your monitor speakers to avoid feedback. As a general rule of thumb; cardioid mics are least sensitive at 180° off axis, whereas hyper-cardioid mics are least sensitive at 160° and 200° (click here for a diagram). By placing your monitor facing the position where your mic is least sensitive, you reduce the amount of sound re-entering the microphone from your monitors and dramatically reduce the chance of feedback.
Other Ways to Reduce Feedback
If all else fails there are several other ways you can deal with troublesome feedback on stage. One common method is to use a graphic equaliser to reduce the level of any particular frequencies that are persistently causing problems. However, one challenge with this method is that if you do this too much, you can end up severely impacting the overall sound quality of your system. Another solution is an automatic feed-back destroyer device. These monitor the output from your mixing desk and when feedback starts, automatically notch out the corresponding frequency. Although both methods work in similar ways, if you do not have a dedicated sound technician, automatic feedback destroyers are a much simpler solution for most singers. One final way is to use a gate on your vocal mic that you can set to switch off the mic when you are not singing. The more singers (and hence microphones) you have on stage, the less headroom you will have in your system before feedback occurs, so it makes sense to reduce the level of any microphones that are not in use. Some vocal processors (such as those by TC-Helicon) contain auto-gates that do this for you and adapt to your singing so you do not have to worry about getting the settings right yourself.
There is no single magic fix to feedback on stage, however by following these steps you should be able to gig without it being an issue, leaving you to focus on one thing – singing!
About The Author:
Chris Kennedy is the principle product reviewer for VoiceCouncil Magazine. He is also a singer-songwriter and composer, performing and writing in a range of styles from rock to jazz. Chris has released several albums as a solo artist and with his group The New Inventions. When he isn’t performing live, Chris also works as a live sound engineer and writes and records film music in his studio. You can find more about him on his website: http://www.chriskennedymusic.co.uk