The linearity of the speaker's response curve is mainly a function of three conflicting parameters: lightness, rigidity, and damping. Currently, only one material permits a joining of these parameters: Beryllium. For domes with identical masses, beryllium is seven times more rigid than titanium or aluminum, the latter two well known for their rigidity. This results in a sound wave propagation three times faster than titanium and two and a half times faster than aluminum. In the end, the linearity of the frequency response curve, the acoustic transparency, and the impulse response of the beryllium tweeter are maximized and offer near-perfect sound.

Flax cones are made of a high-quality flax fiber core enclosed by two thin layers of glass fiber. Flax is twice as light as fiberglass, because the fiber is hollow. It also has very-low elasticity, which makes it ideal to increase the flexural rigidity of the sandwich structure. To design a high-performance diaphragm, you have to optimize a complex set of criteria, which are for the most part contradictory. The composite solution using flax in a sandwich structure with fiberglass skins is a very harmonious way of combining low mass with high internal damping, high velocity of sound, and high flexural rigidity.

The flax cone is made in France exclusively by Focal since 2013. With their original design, the cone is entirely oriented towards acoustic performance. Flax cone are characterized by their natural sound, with low coloration, their richness of reproduction in the midrange register and their tighter bass.