Precision cast and surface treated magnesium cone coupled to a natural rubber surround showing no sign of midrange (edge) resonances. Large magnet system with bumped back plate makes room for extreme coil excursions. Heavy copper rings mounted above and below the T-shaped pole piece reduce non linear and modulation distortion and increase overload margin. 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 reflexion, air flow noise and cavity resonance to a minimum. Gold plated terminals mounted on a glass fibre reinforced plate to reduce contact resistance and improve reliability.