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British company B&W believes it has found a way to improve the sound
fidelity from loudspeakers (WO 98/51121). B&W previously tried using a
tapered pipe at the rear of the vibrating speaker cone to soak up unwanted
sound, but resonances spoilt the effect. So it now puts the cone inside a
plastic sphere, which connects to a tapered tube filled with glass fibre. Using
the sphere pushes the unwanted resonance down to 40 hertz, which lets a single
cone reproduce pure sound in the 200-hertz to 7-kilohertz band.