Fending Off Feedback By: Richard McCoy

November 15, 2013 by Aaron Burger

mb152_131Feedback is one thing all DJs fear. It can disrupt any event and annoy your audience. It can change the mood of an affair in a split second. All of us have at one time or another experienced a feedback problem and noticed the audience reaction to that high-pitched squeal. It is the fastest way to kill the energy of a wedding reception or show.

The good news is, feedback (and its byproducts) can be avoided if you know the correct procedures and methods for defeating it. Feedback is usually caused by a microphone placed in close proximity to a speaker. Many DJs have learned that placing the microphone behind the speakers will eliminate most feedback problems. But there will inevitably be situations where the microphone is used by the DJ or guests somewhere out in front of the speakers. And that creates an environment condusive to feedback.

Specifically, feedback occurs when specific frequencies become “resident” (the same) between the microphone and speakers and are then amplified and re-amplified into an endless loop. mb152_135This is usually a very narrow frequency that is natural for the mic and speaker. Experience will help you learn how to compensate for feedback by using filters (tone controls).

THE HUMAN ELEMENT

You can also defend against feedback with a “preemptive strike,” of tactfull instruction. Many occasional microphone users are unaware of the proper way to use a microphone. Most people have a tendency to hold the microphone far away from their mouth. As a result, you will have to increase the gain (initial volume) of the microphone, input thus increasing the potential for feedback. In this situation, if feedback occurs, then the user reacts by moving the microphone further away from their mouth—which causes the DJ to increase gain and further increases the likelihood of feedback. The reaction to the situation should be that the user moves the microphone closer to their mouth.

There is also situation where an inexperienced mic user will walk right in front of a speaker with their microphone pointed away from their mouth and toward the speaker. This is usually a guaranteed feedback situation.

I believe in instructing all casual users in the proper method of using microphone. You can tactfully coach most people to learn the correct technique. This may eliminate many potential problems but does totally not exterminate the problem.

A MIC PRIMER

Let’s take a look at the microphone itself. There are two basic types of microphones that most DJs use: the dynamic microphone and the capacitor or condenser microphone. Far too often, the selection of a microphone is based upon price rather than the microphone’s specifications or capabilities. However, using a high- quality mic is another way to guard against the beast of feedback.

Dynamic mics can be broken down into two basic categories: Omnidirectional (picking up sound from all directions) or Directional (utilizing various pick-up patterns to focus where the sound hitting the mic is coming from). What this means is that the pattern or ability of the microphone to pick up sounds falls within either a narrow or wide range. Directional microphones use a narrow range or cone to receive input. For voice, this is the best type to use.

For many years the Shure SM58 ($85-$100) has been the best performer and standard for the entertainment industry. It uses a narrow pattern and is well “tuned” to the frequencies of the human voice.

While the SM58 is a wired microphone, wireless microphones are used in most applications where a guest needs to be amplified while making an announcement, giving a toast or speaking in some other way. Since these people are often ignorant of best way to use microphone, providing them with a situation that minimizes the feedback will also help them be appreciated better by the audience.

SPECIAL HELPERS

There are several manufacturers that provide products that will minimize or eliminate feedback most of the time. The best and most guaranteed way to remove feedback is to use a “feedback destroyer” or eliminator designed specifically for that function. These products can, if used correctly, destroy feedback 100% of the time. There are many manufacturers who offer such devices, but Behringer has taken the lead in feedback suppression area. They have produced several models which are very effective in reducing feedback for both microphones and at the system-level. The Shark DSP110 ($85-$100) provides an extremely effective way to eliminate microphone feedback.

This small unit is placed between the microphone and the mixer/amplifier to abolish most if not all microphone feedback problems. The unit is equipped with digital signal processing (DSP) that can detect and filter out those frequencies that will create feedback—before they are actually heard.

I have demonstrated the DSP110’s abilities by holding a microphone directly in front of a speaker WITHOUT ANY FEEDBACK. With the DSP110 disabled, I couldn’t get within 10 feet of the speaker without creating an ear shattering sound. An investment in this small device could save you many embarrassing moments.

As we all know, the acoustics of the room will change as the room is filled with guests. Not only can the DSP110 detect, filter and eliminate feedback frequencies, it also has the ability to “learn” and modify its list of 12 frequencies as the room acoustics change. Initially it is a little difficult to program, but once completed, it will remember your settings and each different venue you perform in.

Behringer also makes several system-level products (DEQ2496, $325-$350) that will not only eliminate all feedback, but provides a whole rack’s worth of flexible equalization, dynamics and time correction functions designed to fix problems and generally optimize sound quality. This product is certainly for the technically orientated DJ but is well worth the investment of money and learning time. This unit can easily be integrated into a system for superior audio quality.

For those on a much smaller budget, there is a Droid RTA app that is very useful for troubleshooting and correcting sound quality. It’s called Audio Tool and sells for about $7.99 at the Android App Store.

Anyway you cut it, the elimination of feedback is another way you can make your show a good as possible, and memorable—in a good way—for the guests. Using the right tools is an indication of true professionalism and can make all the difference in the world.

EDJ WORKSHOP

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Aaron Burger (38 Posts)


Filed Under: Issue #152, Sound