A droplet generator for a continuous stream ink jet print head comprising: an elongate cavity (13) for containing the ink; nozzle orifices (7) communicating from within to without said cavity (13) for passing ink from the cavity (13) to form jets, said nozzle orifices (7) extending along the length of said cavity (13); actuator means (3) for vibrating the ink in said cavity (13) such that each said jet breaks up into ink droplets at the same predetermined distance from its respective nozzle orifice (7), said actuator means (3) being disposed on the opposite side of said cavity (13) to said nozzle orifices (7); and extending between said actuator means (3) and said nozzle orifices (7) a surrounding wall of said cavity (13) for containing the ink between said actuator means (3) and said nozzle orifices (7), said surrounding wall comprising inner and outer constituent walls, the resistive component of the wave impedance of said outer wall being such that the outer wall passively damps vibration of the inner wall by dissipating its vibration, the reactive component of the wave impedance of said outer wall being such that the outer wall actively restrains vibration of the inner wall, said outer wall thereby ensuring that each said jet breaks up into ink droplets at said same predetermined distance from its respective nozzle orifice (7).