An improved method and device for controlling cone breakup (divisional modes) in extended range, cone diaphragm type electromechanical acoustical transducers for reproducing an acoustical signal from a corresponding electrical signal is provided. The transducer assembly includes a low mass cone shaped diaphragm, a voice coil former of 30 mm or less in diameter, and a shaped device no wider than the diameter of the voice coil former and extending into the inner volume of the cone but no taller than the height of the outside edge of the cone. This shaped device defines the shape and volume of a small mass of air within the boundary layer of air where molecular adhesion of air molecules to the cone diaphragm surface becomes a significant variable in the performance of the extended range transducer.