Immersive systems take this a step further by adding speakers on the ceiling to provide more enveloping and realistic surround effects. They can also add more speakers to the front left, center and right speakers already behind the screen, and extra surround speakers in arrays positioned above the existing arrays. These speakers may be set up so they can be addressed individually so that a sound effect can be isolated to one specific speaker. A panning effect can travel smoothly and consistently around the theater, moving among, say, 16 or 20 separate surround speakers instead of among four groups of speakers as in 7.1.