The single full range pure beryllium driver of Focal Utopia headphones.
Focal 6WM UTOPIA-M Mid Bass Drivers
Focal Elegia Headphones at Audio Affair
What are the differences between different electrodynamic loudspeaker drivers? How did AKG / Sennheiser / Focal solve the same problem in different ways? : r/oratory1990
Hifi 40mm Headset Driver For Focal Listen Pro Headphone Speaker 32ohm 120db Titanium Film Earphone Repair Parts Bass On Sale 2pc - Earphone Accessories - AliExpress