Yamaha Digital Audio Systems

How to Eliminate Feedback

Feedback. Well…it is probably the most disliked word in professional audio other than “ground hum” or “power outage.” For our sake we will focus on feedback so as not to create any additional heartaches for our blog readers.

Feedback is created by a loop of audio signal. As shown in the attached picture, the signal enters in the path from the microphone and is then passed into the mixer. After the signal leaves the mixer it enters the amplifier and in turn the speaker cabinet. Out of the speaker cabinet, the same exact signal is “fed back” to the microphone...thus, creating a loop, or that awful sound we like to call “feedback.”




If you don’t already, assume that we highly dislike feedback and we want to get rid of it completely. There are some very easy practices that can help provide the highest gain in your audio system before feedback. In order to have an effective system or process to eliminating feedback we have to focus on reducing any unnecessary gain in your signal path. Here are 4 of the most basic practices that will help eliminate feedback:

1. Make sure that your main speakers are in front of your closest microphone to the audience. This way you are not battling the powerful high frequency drivers in your main speaker cabinets; trust me, those things always win no matter how much of a rockstar audio engineer you are.
2. Do the research, find out what the polar pattern of your microphone is so that you can place your monitor wedges accordingly. For instance, a directional microphone with a cardioid polar pattern (such as a Shure SM58) picks up sound in one direction. Therefore, placing the monitor wedge directly behind the microphone is the best option when trying to eliminate feedback. If you are unsure what polar pattern your microphone uses, call myself or the JSS Team, we are always happy to help. After all, it is what we do.
3. Move the source of sound as close to the microphone as possible. This will help reduce the amount of unnecessary gain in your signal path. Remember, we are focused on creating the most gain before feedback.
4. If the first 3 tips don’t work or you really want to go the extra mile, try “wringing out” your monitor wedges. “Wringing out” is an industry term for using an equalizer, generally a graphic equalizer to attenuate problem frequencies in your system. The simplest way to describe how to do this is install a graphic equalizer in between your mixer’s monitor output and your monitor power amplifier. Make sure that the equalizer is not bypassed and all of the available frequencies are set to zero. Turn the problem sources send all the way down or off. Set the problem sources gain to unity gain. Now slowly raise the send level of the source and you should begin to hear your problem frequencies emerge from the wedge(s). Find them on your equalizer and attenuate them as needed.
   

If you are experiencing an extreme feedback situation, please contact JSS. We are a full service company that can tune your system and provide maintenance that will help ensure that you do not have those same feedback issues. If you have any questions, please contact me. We'll wring out your monitors!

Forrest Colegrove
Account Manager
fcolegrove@jss.net
615.663.4481
www.JSS.net

Shure KSM9

The musicians I am familiar with are always looking for “their sound.” For vocalists, this usually means finding the right microphone for their voice. I generally try to recommend a versatile microphone to my clients that are vocalists and in most cases that ends up being Shure’s KSM9 Vocal Condenser Microphone.

The real difference between the Shure KSM9 and any other high-end handheld condenser microphone on the market is the dual-pattern feature. The Shure KSM9 features both supercardioid and cardioid polar patterns. The benefit to having this feature is that you can find the most natural response for your vocalist. The cardioid polar pattern is more susceptible “proximity effect” than the supercardioid pattern. Proximity effect refers to the change in frequency response of a microphone with a directional polar pattern (cardioid) as the source of the sound is brought closer to the microphone. Explained, when you are using a cardioid pattern and you bring your sound source (vocalist) closer to the microphone, you gain bass response. If you are not in favor of having the additional bass response, you can simply change the capsule to the supercardioid pattern. This dual-pattern feature is also an extremely useful tool for monitor engineers. As the KSM9 provides supercardioid and cardioid the microphone gives the engineer more options on where to place the stage monitors to reduce feedback and provide proper coverage to the musicians.

The KSM9 is the premium choice of live hand-held vocal microphones. Apart from the dual-pattern feature, the Shure KSM9 is available in a Champagne or Charcoal Black finish. Also, the sound quality of the KSM9 is truly unmatched. In fact, even as a live microphone, the KSM9 is often used in recording studios on anything from vocals, to acoustic guitars, to electric guitar cabinets. If you are looking to improve the quality of your live performance or your studio recordings, choose the Shure KSM9. If you have any questions regarding microphone selection, please feel free to contact me directly. Thanks for reading!


Forrest Colegrove
Account Manager
Cell (615) 663-4481
Office (615) 534-1190
Nashville, TN
www.JSS.net