Loudspeakers

Tuned Mass Damping
However stiff you make the cone or dome of a moving-coil drive unit, ideally obviating all 'breakup' resonances within the driver's passband, the roll surround can still let the side down. It has to be flexible to allow cone movement, so is itself subject to bending resonances; and because it forms an annulus around the external diameter of the diaphragm, it represents quite a large radiating area.

The most significant disruption to frequency response occurs when the surround is moving in opposite phase to the cone. Focal's novel solution is to adapt a well-known technique from other fields of mechanical engineering called TMD (tuned mass damping), in which carefully dimensioned and positioned masses act to suppress resonance. In the Utopia's midrange drivers a single 'mass' takes the form of a small rib moulded into the very edge of the roll surround. KH