Winning the Battle Against Feedback

This post is by Adam Levin, part of the team at Chuck Levin's Washington Music Center. We're proud to have Chuck Levin's as one of our great partners!

In addition to their huge store in Wheaton, Chuck Levin's also recently launched an online store so you can get all your gear shipped straight to you. As a special bonus for Flashband membership, use the code FLASH5 to get 5% off any order, any time. 

Feedback. We’ve all heard it, even if you didn’t know what it was called. Feedback is when a single frequency builds up in a sound system to the point of taking over the sound. Ever heard a really high-pitched squeal come through a sound system that made everyone’s ears want to bleed? Or bass that drowns out the entire room and fills it with one solid tone? That’s feedback.

Feedback is a purely physical phenomenon. It is most commonly a relationship between microphones and the speakers that their signals are put through. 

I like to think of it like this: Microphones have a pickup pattern. You may have heard the terms “cardioid” or “omnidirectional” or “hypercardioid” -- these all describe the shape in which a microphone “hears” sound. Think of this shape like a cloud. Speaking generally, whatever is inside this cloud, the microphone hears clearly. Everything outside this cloud will be rejected by the microphone or not picked up.

This is cardioid pickup pattern. This microphone is picking up sound inside the cloud, and rejecting sound straight down the body of the microphone (where there is no cloud).

All microphones have a pickup pattern, and different pickup patterns can be used in different situations on stage.

Speakers put out sound in a pattern as well. In most instances, this is straight out the front of the speaker (where the grill is located) in a 75 to 120 degree pattern when you are looking straight down on the speaker. 

QSC K series speakers, for example. 

Feedback occurs when a microphone can hear itself in one of the speakers. In other words, when the speaker’s cloud crosses the microphone’s cloud and one frequency builds up. 

Here in this illustration we see the feedback occurring right near 2k Hz.

How can you combat feedback? Here are a few tips and pieces of gear that help deal with this beast:

1. Know your microphone. After understanding that feedback is directly related to what your microphone “hears,” it’s important to know what that is. A microphone with a tighter pattern, or a very directional microphone, will help pick up your intended source and block out sound from speakers, monitors, other band members, and rowdy attendees.

The AKG D5 Dynamic Microphone is my go-to mic for tricky situations. It sounds like mics twice the price, with a really tight pattern to make stage life easy and a lifetime warranty. With a price tag under $100, this is a worthwhile investment.

Feel like being cool and pointing your microphone toward the crowd? Or walking into the crowd? Be careful not to point your microphone where a speaker is blasting back at you! This will make you very uncool when everyone’s ears are bleeding due to excessive feedback!

Position your monitors (or move your mic stand) to a position where your microphone is not picking up audio from the monitors (or not in the “cloud”). You can see these points when referencing your microphone’s pickup pattern; these will be the points where there is no “cloud.”

2. Consider a Feedback Suppressor/Destroyer. There is a whole world of products and devices out there that will “squash” the feedback for you, or at least help you detect it. Think of these as automatic EQs that hunt out the trouble frequency and turn only that frequency down. Higher-end models will turn down only that specific trouble frequency. Less expensive models will grab a wider set of frequencies that might make an an audible difference in your tone, but at least the feedback will be gone.

The Behringer FBQ100 is the easiest stand-alone solution. Plug your mic straight into the back, and plug another XLR cable out and into the soundboard. This little guy will squash the feedback for you and give you some other useful little tools that every vocalist might find useful. At under $100, this is a valuable and portable tool to keep on hand.

3. And Some In-Ear Monitors. This is a little more advanced and is not for everyone, but one of the key culprits of feedback are those stage monitors that lay in front of you. Remove the stage monitor and put it in your ear, and you have the basic workings of an In-Ear monitor system… and have significantly cut back on feedback sources! There are wired and wireless versions depending on your budget and your needs.

The Shure PSM300 brings top-of-the-line technology down to a moderately affordable price point. If you want to know more about In-Ears and if they are for you, give us a call and we’ll guide you in the right direction.

Don’t "cup" your microphone!! We’ve seen all the pros and stars do it...

But when you hold the microphone like this, you are actually changing the pickup pattern! This mic technique will change the pattern from directional (picking up in the front) to omnidirectional (picking up sound EVERYWHERE: no rejection points). This will lead to feedback in most situations. It may look cool for a photo, but it’s never cool to feedback!

If you’re ever having problems with sound and are not sure how to figure it out, give us a call! We’re more than a store at Chuck Levin’s Washington Music Center; we are a resource and we’re here to help you get the best sound you can at every gig.