Horns are mainly used in PA systems, as they require the best sound distribution possible so the audience can hear everything. Horns distribute the powerful high or mid frequencies of a compression driver in the preferred direction. The angle at which the sound leaves the speaker is referred to as the dispersion angle, and is measured in degrees. The strongest horns are made of metal and the lightest horns are made of synthetic materials. Sometimes you'll need a driver adapter in combination with a horn and a compression driver.