 Some speaker driver designs have provisions to do so (typically termed servomechanisms); these are generally used only in woofers and especially subwoofers, due to the greatly increased cone excursions required at those frequencies in a driver whose cone size is well under the wavelength of the some of the sounds it is made to reproduce (ie, bass frequencies below perhaps 100 Hz or so).Speaker drivers may be designed to operate within a broad or narrow frequency range.Small diaphragms are not well suited to moving the large volume of air that is required for satisfying low frequency response.