Abstract: Extended frequency range Helmholtz resonators particularly useful for sound absorption over a relatively wide frequency range are disclosed. The resonators are conventional Helmholtz resonators with the addition of an active acoustic driver in the resonator cavity driven at appropriate amplitudes, frequencies and phases to provide a high degree of absorption of sound not only at the resonant frequency of the resonator, but for substantial frequency bands above and below the resonant frequency. To provide the active drive to the acoustic driver in the resonant cavity, one or more microphones are used to detect the sound to be absorbed, which signal is processed and amplified to provide a drive to the acoustic driver to best absorb the incoming sound. Various embodiments are disclosed.