How to Prevent Feedback on Stage When Running Live Sound: Tips and Techniques

Live sound engineers know that feedback is one of the most frustrating problems that can occur during a performance. It can ruin the sound quality and distract the audience from the performance. Feedback is caused by the sound from the speakers being picked up by the microphones and then amplified again. This creates a loop that results in a loud, high-pitched noise.

Fortunately, there are several methods that can be used to prevent feedback on stage. One of the most effective methods is close miking. This involves placing the microphones as close as possible to the sound source. This reduces the amount of gain that is required and minimizes the chance of feedback. Another method is to ring out the microphones. This involves setting proper gain and bringing up the mic in the PA or monitor speakers until it begins to feedback. Remove the offending frequency and bring up the mic until the next frequency feeds back and remove that.

Live sound engineers should also be aware of the importance of providing space between microphones and speakers. The most effective way to increase a system’s maximum gain before feedback is to create more distance between the microphone and the speakers. It’s also important to keep each mic as close to its source as possible to reduce the need for the sound engineer to have to add gain at the mixing desk for the PA, and it reduces stray signals from being picked up by the mic. By following these methods, live sound engineers can prevent feedback and ensure a high-quality performance.

Understanding Feedback

Feedback, also known as “howlround” or “squeal,” is a common problem in live sound. It occurs when sound from a loudspeaker re-enters the sound system through an open microphone, creating a loop of amplified sound that can quickly become out of control. Feedback can be a frustrating and embarrassing problem for performers and sound engineers alike, but it can be prevented with the right techniques and equipment.

Feedback is caused by a combination of factors, including microphone placement, room acoustics, and system gain. Microphone placement is a critical factor in feedback prevention. Close miking is generally the way to go for loud stages and busy rooms, as it offers maximum gain before feedback. However, it might not always be the best for sound quality. Remember, with each doubling of distance, sound level is cut in half.

Room acoustics also play a significant role in feedback prevention. The shape and size of the room, as well as the materials used for walls, floors, and ceilings, can affect the way sound travels and reflects. Soft materials, such as curtains and carpets, can help absorb sound and reduce the risk of feedback. Hard surfaces, such as concrete walls and floors, can reflect sound and increase the risk of feedback.

System gain is another critical factor in feedback prevention. Gain is the amount of amplification applied to a signal, and it can be adjusted using a mixer or amplifier. Too much gain can lead to feedback, while too little gain can result in a weak or distorted sound. Finding the right balance between gain and volume is essential for preventing feedback.

By understanding the causes of feedback and taking steps to prevent it, performers and sound engineers can ensure a smooth and successful live sound experience.

Sound Equipment Setup

When it comes to preventing feedback on stage during live sound, proper sound equipment setup is crucial. This section covers two essential sub-sections: Proper Microphone Placement and Sound Check and Levels.

Proper Microphone Placement

Proper microphone placement is key to preventing feedback. Here are some tips to keep in mind:

  • Close miking: For loud stages and busy rooms, close miking is generally the way to go. It might not always be the best for sound, but for the maximum gain before feedback, you have to kiss the mic. Remember, with each doubling of distance, sound level is cut in half. source
  • Keep speakers in front of microphones: A basic rule of thumb to remember is to keep the speakers in front of the microphones (rather than behind) to prevent feedback. Feedback is what happens when a microphone picks up too much of its signal. source
  • Use directional microphones: Directional microphones, such as cardioid or hypercardioid microphones, can help to reject sound from the sides and rear, which can help to prevent feedback. source

Sound Check and Levels

After setting up the microphones, it’s essential to perform a sound check and set the levels correctly to prevent feedback. Here are some tips to keep in mind:

  • Start with default settings: The first step is to normalize the mixer by setting all the settings to their default. This will help to make sure that you don’t encounter any surprises left for you by the person who used it last and it’ll make sure that you’re starting with a blank slate. source
  • Check for feedback: During the sound check, it’s important to check for feedback by gradually increasing the volume of each microphone and checking for any unwanted sounds. If feedback occurs, adjust the levels or microphone placement accordingly.
  • Use a graphic equalizer: A graphic equalizer can help to control feedback by allowing you to adjust the levels of specific frequencies. source

By following these tips for proper microphone placement and performing a thorough sound check, you can prevent feedback on stage and ensure a successful live sound performance.

Utilizing Sound Dampening Techniques

When it comes to live sound, preventing feedback is essential to ensure a successful and enjoyable performance. One effective way to prevent feedback is by utilizing sound dampening techniques.

Acoustic Treatments

Acoustic treatments are designed to absorb sound waves and reduce the amount of sound reflections in a room. This can help to prevent feedback by reducing the amount of sound that is bouncing back into the microphones. Some common acoustic treatments include:

  • Acoustic panels: These panels are made of sound-absorbing materials and can be placed on walls, ceilings, and floors to reduce sound reflections.
  • Bass traps: These traps are designed to absorb low-frequency sound waves and can be especially useful in preventing feedback from bass instruments.
  • Diffusers: These devices are designed to scatter sound waves and can help to reduce the amount of sound reflections in a room.

By using acoustic treatments, live sound engineers can create a more controlled acoustic environment that is less prone to feedback.

Sound Barriers

Another effective way to prevent feedback is by using sound barriers. Sound barriers are designed to block sound waves and can be especially useful in preventing sound from bleeding into microphones. Some common sound barriers include:

  • Sound curtains: These curtains are made of sound-blocking materials and can be hung around a stage or performance area to prevent sound from bleeding into microphones.
  • Acoustic shields: These shields are placed around individual microphones and can help to prevent sound from bleeding into the microphone from other sources.

By using sound barriers, live sound engineers can create a more isolated acoustic environment that is less prone to feedback.

Overall, utilizing sound dampening techniques can be an effective way to prevent feedback and ensure a successful live sound performance.

Implementing Sound Equalization

Equalization is an essential technique for managing feedback in live sound. It allows sound engineers to adjust the balance between the frequency components of an electrical signal, which is created when the sound hits a microphone. By manipulating the frequency response of the sound system, sound engineers can reduce the likelihood of feedback and improve the overall sound quality.

Using Equalizers

Equalizers are devices that allow sound engineers to adjust the frequency response of a sound system. They can be either hardware or software-based and are typically used to filter out unwanted frequencies or boost specific frequencies to achieve a desired sound.

When using equalizers to prevent feedback, it is important to identify the frequency ranges that are most prone to feedback. This can be done by using a graphic equalizer to sweep through the frequency range while monitoring for feedback. Once the problematic frequencies have been identified, they can be attenuated using a notch filter or a parametric equalizer.

Frequency Adjustments

In addition to using equalizers to filter out problematic frequencies, sound engineers can also make frequency adjustments to reduce the likelihood of feedback. For example, reducing the low-frequency content of a sound system can help to prevent feedback caused by low-frequency rumble. Similarly, reducing the high-frequency content of a sound system can help to prevent feedback caused by high-frequency whistles.

It is important to note that frequency adjustments should be made sparingly, as excessive adjustments can lead to an unnatural sound. Sound engineers should also be aware of the overall frequency response of the sound system, as changes to one frequency range can affect the balance of the entire system.

Overall, implementing sound equalization is an effective way to prevent feedback in live sound. By using equalizers to filter out problematic frequencies and making frequency adjustments as necessary, sound engineers can achieve a natural and balanced sound while minimizing the risk of feedback.

Training Your Crew

When it comes to preventing feedback on stage, it’s not just the sound engineer who needs to know what they’re doing. The entire crew needs to be trained on sound engineering principles and feedback identification.

Sound Engineering Principles

The crew should be familiar with basic sound engineering principles, such as microphone placement, gain staging, and EQ. They should understand how to set up a sound system properly and how to troubleshoot common issues. This will help prevent feedback from occurring in the first place.

Feedback Identification

The crew should also know how to identify feedback when it does occur. They should be able to recognize the telltale signs of feedback, such as a high-pitched whine or a low rumble. They should also know how to locate the source of the feedback and how to eliminate it.

To help crew members learn these skills, it may be helpful to provide training sessions or workshops. These can be led by experienced sound engineers or by outside professionals. In addition, crew members should be encouraged to ask questions and seek out additional resources to improve their knowledge and skills.

By training the entire crew on sound engineering principles and feedback identification, you can help prevent feedback from occurring and ensure that your live sound events go smoothly.

Investing in Quality Equipment

When it comes to live sound, investing in quality equipment can make a huge difference in preventing feedback. Here are a few things to consider when choosing equipment:

Choosing the Right Microphones

The type of microphone used can greatly affect the amount of feedback that occurs. Dynamic microphones are less sensitive than condenser microphones, making them a good choice for live sound. Additionally, directional microphones, such as cardioid or supercardioid, can help reduce feedback by picking up sound primarily from the front and sides and rejecting sound from the rear.

High-Quality Sound Systems

Using a high-quality sound system can also help prevent feedback. Look for systems with high signal-to-noise ratios and low distortion levels. It’s also important to ensure that the system is properly matched to the venue and the number of people in attendance. A system that is too small for the space may need to be turned up too high, increasing the likelihood of feedback.

Investing in quality equipment may require a larger upfront cost, but it can ultimately save time and frustration by reducing the occurrence of feedback.

Regular Equipment Maintenance

Regular equipment maintenance is essential to prevent feedback on stage during live sound performances. Neglecting equipment maintenance can lead to equipment failure and unwanted noise, which can ruin a performance.

Routine Checks

Performing routine checks on equipment is important to ensure that everything is in good working condition. Here are some routine checks that should be done regularly:

  • Check all cables for damage, kinks, or frayed ends. Replace damaged cables immediately.
  • Check all connectors and jacks for tightness. Loose connections can cause unwanted noise and feedback.
  • Check all speakers and monitors for any signs of wear and tear. Replace any damaged speakers or monitors immediately.
  • Check all microphones for any signs of damage. Replace any damaged microphones immediately.

Timely Repairs

Timely repairs are necessary to prevent equipment failure and unwanted noise. Here are some repairs that should be done as soon as possible:

  • Repair or replace any damaged cables, connectors, or jacks immediately.
  • Repair or replace any damaged speakers or monitors immediately.
  • Repair or replace any damaged microphones immediately.
  • Clean all equipment regularly to prevent the buildup of dust and debris.

Regular equipment maintenance and timely repairs can help prevent feedback on stage during live sound performances. By taking care of equipment, performers and sound technicians can focus on delivering a great performance without worrying about unwanted noise or equipment failure.

Conclusion

Preventing feedback on stage is crucial for a successful live sound performance. By following the tips and techniques outlined in this article, sound engineers and performers can significantly reduce the risk of feedback and ensure a high-quality sound experience for the audience.

One of the most effective ways to prevent feedback is through proper microphone placement. Close miking, where the microphone is placed as close to the sound source as possible, can help achieve maximum gain before feedback. Additionally, using directional microphones and avoiding pointing them towards speakers or monitors can also help reduce feedback.

Another important factor to consider is the use of EQ. By identifying and cutting problem frequencies, sound engineers can reduce the risk of feedback while still maintaining a balanced sound. It’s important to note, however, that excessive EQ cutting can negatively impact the overall sound quality.

In addition to microphone placement and EQ, sound engineers can also prevent feedback by properly setting up monitors and speakers and using sound-absorbing materials on stage. By taking a comprehensive approach to sound management, performers and sound engineers can create a feedback-free environment that allows for a seamless and enjoyable live sound experience.