https://www.livingvoice.co.uk/interview-kevin-scott-vox.html
“Q: What about the drive units?
The Bass driver is a 15” unit with a powerful 6kg Al Ni Co magnet assembly and a stiff, light conical paper diaphragm. This driver is loaded through a complex faceted phase plug into the throat of the folded exponential bass horn.
The Mid driver has a powerful 6kg Al Ni Co magnet structure to control a 75mm chemically hardened aluminium diaphragm with integrated former onto which the voice coil is wound. The diaphragm loads to the 300Hz mid-range radial exponential horn through a complex radial phase plug.
The HF driver uses a powerful Al Ni Co magnet structure and a complex phase plug. The diaphragm and former are made from a single piece of vacuum deposited atomised Beryllium. This is a very high tech process that allows the production of a diaphragm with vanishingly low mass and remarkable stiffness and it allows the 48mm diaphragm to operate up to 22kHz.
The Super HF driver uses a powerful Rare-earth cobalt magnet structure, a 35mm vacuum deposited atomised Beryllium diaphragm loaded through a complex radial phase plug into a slot dispersive horn. This unit operates up to 45kHz.”