Definitive Technology DT Series 6.5STR Stereo In-Ceiling SpeakerDefinitive Technology DT Series 6. 5STR Stereo In Ceiling Speaker. This Definitive Technology DT Series DT 6. 5STR in ceiling speaker features a dual function design that doubles as a single stereo speaker or part of a surround sound system. The slim grille and bezel enable seamless installation in your home. Features: Annealed aluminum tweeter along with Mylar capacitors provide rich, pure highs. 6. 5" composite polypropylene driver cone with rubber