Enjoy powerful sound anywhere Enjoy deep, punchy sound wherever you like with your EXTRA BASS™1 speaker. Dual passive radiators work together with full-range speakers to enhance low-end tones, giving bass a boost. Ready for anything The SRS-XB33 is seriously tough, giving you the freedom to party wherever and whenever you like. X-Balanced Speaker Unit Developed by Sony, the X-Balanced Speaker Unit achieves high sound quality and powerful sound pressure for a richer, deeper, more rewarding listening experience. What is the X-Balanced Speaker Unit? Unlike the circular diaphragm in a conventional speaker unit, the newly developed X-Balanced Speaker Unit in the XB33 features a non-circular diaphragm.