Project 21 is an extensive project consisting of a satellite two-way with a bass enclosure. All drivers are driven actively through a DSP-based crossover. Four-channel level controls are used at each speaker location, which are RF-remote controlled. This is a joint project from Jean-Claude Gaertner and Jan Didden. In Part I Jean-Claude discusses the design considerations and prototype measurements of the satellites. He shows extensive measurement results on the chosen drivers as well as the completed satellite, response simulations and satellite construction details.