Nanoparticles can be synthesized by precipitation. State-of-the-art is the precipitation of nanoparticles in stirred tanks or high-pressure T-mixers. The study presents two new reactor concepts for continuous precipitation of nanoparticles. Both of them utilize ultrasonic sound as a mixing accelerator. The first reactor has a conical chamber, which is used to study the micromixing quality, the micromixing time, the cavitation intensity and the precipitation of barium sulfate nanoparticles. The second reactor has a so-called cavitational chamber, which is an optimized conical reactor. Both reactors are compared with each other. Additionally a possibility for the scale-up is shown.