Abstract: A droplet generator for a continuous stream ink jet print head has a cavity for containing ink, and nozzle orifices passing ink from the cavity to form jets. An actuator means vibrates the ink in the cavity such that each jet breaks up into ink droplets. The actuator means is disposed on the opposite side of the cavity to the nozzle orifices, and a surrounding wall of the cavity extends between the actuator means and nozzle orifices for containing the ink therebetween. The surrounding wall has inner and outer constituent wall. The resistive component of the wave impedance of the outer wall passively damps vibration of the inner wall by dissipating its vibration; the reactive component of the wave impedance of the outer wall actively restrains vibration of the inner wall, ensuring that each jet breaks up into ink droplets at the same predetermined distance from its respective nozzle orifice.