Abstract: A 4? steradian omni directional tweeter has a closed hollow body acting as a dynamic reflector connected at the center topside of a diaphragm. A piezoelectric element or a voice coil drives the diaphragm. The closed hollow body can be sphere, spheroid, prolate spheroid, ellipse, ellipsoid, prolate ellipsoid, cylindrical, oblate shape, egg shape. In one embodiment, the closed hollow body is made of substance that has a light, rigid, seamless and uniform thickness similar to a bird or chicken egg. The dynamic reflector in the present invention moves simultaneously with its diaphragm to produce an omni directional radiation pattern. Compared with a static reflection system, the dynamic reflection system provides better phase response. Hence the reproduced sound is more realistic, has better precision, clarity and staging.