A small ceiling speaker system comprising an acoustic diffuser wherein said acoustic diffuser comprises: i. a diffuser barrel comprising a cylindrical shell; ii. two opposed circumferentially-spaced apart sets of internal diffuser threads (204 and 306), each set extending no more than ninety degrees around an internal surface of said diffuser barrel; iii. a circumferential flange extending radially inward and outward from a lower end of said diffuser barrel; iv. a plurality of diffuser element supports extending radially inward from a radially inward extending portion of said circumferential flange; and converging on, and of one piece with, an axially central hub; and v. a threaded bore in said hub; vi. a diffuser element, said diffuser element comprising: (a) a body having a circular circumference; (b) an upper radially symmetric outwardly descending diffuser surface on said body; (c) a plurality of demarcations on said upper radially symmetric outwardly descending diffuser surface; (d) a plurality of radial grooves in said upper radially symmetric outwardly descending diffuser surface, each positioned to receive one diffuser element support of said plurality of diffuser element supports; (e) a flat lower surface on said body; (f) a circumferential rim on said lower surface of said body; (g) a central bore through said body in three diameters configured to receive a coiled spring, a fastener extending through said coiled spring, and a fastener head; wherein said fastener comprises a threaded portion sized to extend through and beyond said central bore and threaded into said threaded bore of said hub; wherein rotation of said fastener adjusts a distance between said diffuser element and the flange and thereby the size of an acoustic port of said diffuser. i. a diffuser barrel comprising a cylindrical shell; ii. two opposed circumferentially-spaced apart sets of internal diffuser threads (204 and 306), each set extending no more than ninety degrees around an internal surface of said diffuser barrel; iii. a circumferential flange extending radially inward and outward from a lower end of said diffuser barrel; iv. a plurality of diffuser element supports extending radially inward from a radially inward extending portion of said circumferential flange; and converging on, and of one piece with, an axially central hub; and v. a threaded bore in said hub; vi. a diffuser element, said diffuser element comprising: (a) a body having a circular circumference; (b) an upper radially symmetric outwardly descending diffuser surface on said body; (c) a plurality of demarcations on said upper radially symmetric outwardly descending diffuser surface; (d) a plurality of radial grooves in said upper radially symmetric outwardly descending diffuser surface, each positioned to receive one diffuser element support of said plurality of diffuser element supports; (e) a flat lower surface on said body; (f) a circumferential rim on said lower surface of said body; (g) a central bore through said body in three diameters configured to receive a coiled spring, a fastener extending through said coiled spring, and a fastener head; wherein said fastener comprises a threaded portion sized to extend through and beyond said central bore and threaded into said threaded bore of said hub; wherein rotation of said fastener adjusts a distance between said diffuser element and the flange and thereby the size of an acoustic port of said diffuser. (a) a body having a circular circumference; (b) an upper radially symmetric outwardly descending diffuser surface on said body; (c) a plurality of demarcations on said upper radially symmetric outwardly descending diffuser surface; (d) a plurality of radial grooves in said upper radially symmetric outwardly descending diffuser surface, each positioned to receive one diffuser element support of said plurality of diffuser element supports; (e) a flat lower surface on said body; (f) a circumferential rim on said lower surface of said body; (g) a central bore through said body in three diameters configured to receive a coiled spring, a fastener extending through said coiled spring, and a fastener head; wherein said fastener comprises a threaded portion sized to extend through and beyond said central bore and threaded into said threaded bore of said hub;