ISU 690

Membrane shape and materials are essential. For the finest treble, our engineers have patented the inverted dome tweeter, a Focal signature. The inverted dome shape offers the advantage of low directionality and a small-diameter, lightweight coil for better acceleration. As for the materials used, they combine the key points of a good loudspeaker: aluminum increases dome rigidity and reduces distortion, while the addition of magnesium provides excellent damping. The surround that connects the dome to its support uses Poron, a shape-memory material. This surround is derived from the famous Utopia Beryllium tweeter, and reduces distortion by a factor of three between 2000 Hz and 3000 Hz, where the ear is most sensitive.

The diaphragm, the key component of a loudspeaker, is at the heart of our acoustic engineers' research. Polyglass technology, exclusive to Focal, consists of applying fine glass microbeads to a cellulose pulp cone. This process reconciles the excellent damping of paper with the rigidity of glass. The stiffness index is almost 10 times that of polypropylene. Adjusting the mass-rigidity-damping ratio results in a remarkably linear frequency response curve, right from the membrane design stage. This innovation also significantly increases definition in the midrange register.