Use a 31-band stereo graphic equalizer if you are an audio mastering engineer or an audiophile. This type of equalizer gives the listener control over the entire frequency spectrum, ranging from 20 Hz to 20 kHZ, for both stereo channels. Equalizers with this many bands typically feature high- and low-cut filters and gain controls for increasing or reducing a given signal.
Use a 10-band equalizer for listening to music in a car, computer gaming or for home entertainment systems. While it is possible to use a 31-band equalizer in these applications, the typical enthusiast will not hear much difference when making adjustments to the frequency spectrum using a 10-band graphic equalizer. Even though this type of equalizer has fewer channels, users still have control over the entire audio spectrum from 20 Hz to 20 kHz, which is the normal range of human hearing, but each frequency band has a wider range.
Use a three-band EQ if you need to reduce errant bass or treble frequencies, such as if you are listening to music on a cheap stereo and the speakers can't handle the bass or are making the high frequencies too tinny. Three-band equalizers feature adjustment knobs for high, mid- and low frequencies. Reducing the mid-frequency, for example, helps eliminate the muddy sounds and accentuates the high and low frequencies.