Abstract: When the concept of active modal control is applied to sound field control in enclosures,effective sampling and re——construction of the spatial field are the main problems that have to be solved theoretically.It is even more important to realize a stable and controllable system in experiment.In this paper,a conceptual theoretical analysis for active modal control in an enclosed sound field is given.Various methods are used to compensate the potential unstable poles of the applied feedback control system.A series of experimental results are obtained and discussed,by which some of the the natures of active modal control systems are delineated.