Original Factory Radian Diaphragm 1750PB for Most 1.4" & 2" Radian PB or ZT Drivers 16 Ohm. Also Used On 636PB, 651PB, 745PB, 835PB, 850PB Except 760NEOPB, 745NEOPB, 950PB. Specs. Overall Frame Diaphragm Diameter: 5.9" (150mm) Voice Coil Diameter: 2.92" (74.4mm) Diaphragm Material: Aluminium Alloy Dome with Vented Mylar Surround Nominal Impedance: 16 ohms