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 the best equalization curve for a speech sound reinforcement system?

The response above 2kHz rolls off 3dB for each octave, i.e. -3dB at 4kHz; -6dB at 8kHz; -9dB at 16kHz. The response from 125Hz to 2kHz is flat with a window of ±2dB. Frequencies below 125Hz are rolled off to minimize rumble/boominess. This curve is based on human hearing and perception research.  

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.  

What to do if feedback occurs before the sound system is loud enough? 

*     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.