One of the main issues limiting the performance of practical active sound control systems is acoustic output power limitations of real loudspeakers. Various loudspeaker characteristics and parameters are considered with respect to active sound control requirements. Issues such as loudspeaker resonant frequency, Q, nonlinearities, excursion limitations, thermal power, and group delay are discussed. Some discussion of required or resulting controller solutions is included to illustrate the effects of each parameter or characteristic on performance. Finally, a practical set of desirable loudspeaker characteristics is suggested to provide improved performance of active sound control systems.