Used - Please review pictures for conditionFOCAL 13W7653 order no. fa-X13W7653 31 cm bass driver with high quality cone. The basket is made of die-cast. To avoid compression effects the driver possesses a pole piece hole. The spider is rear ventilated for better cooling. resonance frequency fs = 45,99 Hz impedance R = 4 Ohm sound pressure level SPL = 90,39 dB (2,83V; 1m) DC resistance Re = 3,2 Ohm force factor BL = 18,38 N/A effective piston radiating area Sd = 530,93 cm2 effective mechanical mass incl. air load mms = 153,51 g equivalent volume of compliance Vas = 30,89 l total Q factor Qts = 0,39 (Qms=5,61, Qes=0,42) mounting diameter d = 289 mm overall diameter d = 335 mm mounting depth (not countersunk) t = 172 mm mass m = 9,1 kgrecommended cabinet 1: closed cabinet with 9,1 L volume from 90/57 Hz (-3dB/-8dB) recommended cabinet 2: 34 L volume bass reflex cabinet with HP100 reflex tube, 24 cm long. from 44/36 Hz (-3dB/-8dB).