In the pro audio world, a 15 band equalizer can be your best friend, or your worst enemy. A 15 band equalizer has the ability to raise or lower the presence of any of 15 different frequencies. In addition, in this section you will find 15 band equalizers that are mono, meaning they are only designed for one channel (usually used on a single floor monitor, or for large PA systems that are typically run in mono anyway). You will also find dual 15 band equalizers, meaning that the unit will process TWO channels, these can be two floor monitors in a PA system, or the left and right channel in a stereo PA or DJ system.
One thing to consider when using a pro audio equalizer, STOP making the happy face! We have all seen it, where an equalizer is bumped up to the extreme on both the low frequencies, and the high frequencies. Try and stop this madness. If possible, equalizers should only be used to subtract from the audio signal rather than add to it. For example, the "0" mark on the equalizer means that it is not adding any signal to a frequency, nor is it taking anything away from a certain frequency. If you find that you want to use that smiley face on your equalizer, bring down the middle frequencies below the "0" (properly called unity) line. You are accomplishing the same goal, the lows and highs stand out more, but the difference is you are not pushing your woofer and high frequency compression driver into oblivion.