michael chuaMay 8, 2018HIFI DRIVERS4", Midrange, PL11MH09-08, Premium Line, Vifa Vifa PL11MH09-08 Thiele / Small Parameters Sealed Box 1 liters. F3=160Hz, Q=0.81 Sealed Box 1.5 liters. F3=156Hz, Q=0.71 Sealed Box 2 liters. F3=160Hz, Q=0.65 Ported Box 3 liters. F3=90Hz Ported Box 5 liters. F3=75Hz