Often the standard surround channels are misconceived to be "rear channels" when they are in fact meant to be placed at 90-120 degrees. In commercial cinema, where there is a large area to cover, it would be impractical to use a single speaker for each surround channel. Theater auditoria are often lined with speakers all along the side and back walls. This is to increase the size of the listening area. JBL states that surround speakers should be spaced evenly along the side and back walls, starting at no closer than 1/3 of the room length from the screen (so the surrounds do not interfere with the front channels) and should be located at about 10–12 feet high and angled down to face the opposite wall-floor boundary.