DESC: Taking advantage of Infinity's Metal Matrix Diaphragm (M.M.D.) driver technology, the TSS-750 5.1 speaker package delivers spine-tingling surround sound performance for movies and multichannel music. Unlike other driver materials in this price range, M.M.D. woofers and tweeters consist of a stiff aluminum core for exceptional strength and rigidity. M.M.D. is derived from the C.M.M.D. material used on Infinity's flagship Prelude speakers, and it translates into distinctly cleaner and more realistic sound.