Line arrays can be oriented in any direction, but their primary use in public address is in vertical arrays which provide a very narrow vertical output pattern useful for focusing sound at audiences without wasting output energy on ceilings or empty air above the audience. A vertical line array displays a normally wide horizontal pattern useful for supplying sound to the majority of a concert audience. Horizontal line arrays, by contrast, have a very narrow horizontal output pattern and a tall vertical pattern. A row of subwoofers along the front edge of a concert stage can behave as a horizontal line array unless the signal supplied to them is adjusted (delayed, polarized, equalized) to shape the pattern otherwise. Loudspeakers can be designed to be arrayed horizontally without behaving as a horizontal line source.