A double treated, hard paper cone which is designed to be very stiff without losing the damping capability, together with a natural rubber surround produce a well behaved roll off characteristic and reduce potential resonance problems. A large magnet system with a bumped back plate together with a long 4-layer voice coil gives long linear excursion. The magnet system has a Tshaped cross section of the pole piece for low modulation distortion. Extremely stiff and stable injection moulded metal basket keeps the critical components in perfect alignment. Large windows in the basket both above and below the spider reduce sound refl exion, air fl ow noise and cavity resonances.