Equalization: Selectively boosting or cutting bands of frequencies to improve the performance of a sound reinforcement system.
What equalization can do when used properly
- Noticeably, but not dramatically, improve the naturalness or intelligibility of a sound reinforcement system by emphasizing the frequency ranges most critical for speech.
- Noticeably, but not dramatically, increase the overall output level of a sound reinforcement system by reducing the system's output in the frequency bands at which feedback occurs. These frequency bands will differ from system to system based on many variables, including room acoustics, microphone placement/design, loudspeaker location/design, even air temperature.
What equalization cannot do
- Make a poorly designed sound reinforcement system work satisfactorily. Every well-designed sound reinforcement system is subject to the laws of physics described by the Potential Acoustic Gain equation.
- Improve intelligibility problems caused by reverberation, reflections, mechanical vibration, high background noise levels, or other problems caused by the location or physical design of the room. These problems are acoustical in nature and cannot be solved electronically. They must be resolved with acoustical solutions, such as sound absorbent panels and heavy drapes.
- Improve intelligibility problems caused by the talker being too far from the microphone.
- Improve the performance of sub-standard audio components in the sound reinforcement system.
- Eliminate distortion or noise problems caused by mismatched audio levels between system components.
- Improve echo return problems in teleconferencing systems.
How to approach equalization
Approach equalization gently and slowly! After every adjustment, listen carefully to the resulting sound. The goal is to improve sound quality as well as increase the gain before feedback. When the system is loud enough and/or clear enough, stop equalizing! Also, stop equalizing and examine the complete sound reinforcement system in detail whenever the equalization causes a degradation in the sound quality.
What is acoustic feedback?
Acoustic feedback occurs when the amplified sound from any loudspeaker re-enters the sound system through any open microphone and is amplified again and again and again.
What can make feedback problems worse?
- Placing loudspeakers too close to microphones.
- Too many open microphones.
- Boosting tone controls indiscriminately.
- Room surfaces that are hard and reflective such as glass, marble, wood.
- Request that the talker speak louder into the microphone.
- Reduce the distance from the talker to the microphone. Each time this distance is halved, the sound system output will increase by 6dB.
- Reduce the number of open microphones. Each time this number is halved, the sound system output can be increased by 3dB.
- Move the loudspeaker farther away from the microphone. Each time this distance is doubled, the sound system output can be increased by 6dB.
- Move the loudspeaker closer to the listener. Each time this distance is halved, the sound system output will increase by 6dB.
- Use an equalizer/feedback reducer to cut the frequency bands in which the feedback occurs. The sound system output will typically increase 3 to 9dB.
You can find great information like this – along with other useful tools (like a Cable Selector and an audible Noise Identifier), our Tech Library and even downloadable Wireless Workbench software – in the Tech Support section of the Shure website.