Blitzby Apple Watch Screen Protector 44mm Plus One woofer cones. The Kappa 63.9i 6-1/2-Inch 3-way speakers feature light, but stiff woven glass-fiber woofer cones that won't flex or distort. This patent pending technology deliver a cone with more surface area than competing models of the same size. The Kappa 63.9i 6-1/2-Inch 3-way speakers feature light, but stiff woven glass-fiber woofer cones that won't flex or distort. Plus One woofer cones This patent pending technology deliver a cone with more surface area than competing models of the same size.