A type of loudspeaker driver intended to produce high frequencies, typically those above 2,000Hz. Soft dome tweeters, invented in 1967 by Bill Hecht, are based around a voice coil that is free to move within a magnetic field. The magnetism in the voice coil varies with the audio signal, moving the coil against the fixed magnetic field. The coil is attached to a diaphragm – in the case of a soft dome tweeter, resin-impregnated silk or other fabric formed into the shape of a dome – which moves as the coil moves, creating sound waves in the air. Unlike low-frequency drivers, dome tweeters do not have a basket or frame, consisting of a plate that attaches to the magnet. Soft dome tweeters are characterized by good accuracy and linear response, with a wide dispersion pattern.