The information is then passed to an amplitude matrix that develops the speaker feeds, via a set of shelf filters, which improve the accuracy and performance of the decoder in smaller listening environments (they can be omitted in larger-scale applications). Ambisonics was designed to suit actual living rooms and practical speaker positions: most living rooms are rectangular and as a result the basic system was designed to decode to four loudspeakers in a rectangle, with sides between 1:2 (width twice the length) and 2:1 (length twice the width) in length, thus suiting the majority of living rooms. A layout control is generally provided to allow the decoder to be configured for the loudspeaker positions - an important aspect of Ambisonic replay where it differs from other surround systems: the decoder is specifically configured for the size and layout of the speaker array. The layout control may take the form of a rotary knob, a 2-way (1:2,2:1) or a 3-way (1:2,1:1,2:1) switch.