SB ACOUSTICS SB29NRX2-00, 29cm NOREX PAPER CONE PASSIVE RADIATORFeatures Hard paper cone for improved piston operation (made in-house) Cast aluminum chassis for optimum strength Low damping medium hardness rubber surround for improved dynamic linearity and mechanical stability Easily adjustable moving mass Specs Effective piston area, Sd 312 cm2 Free air resonance, Fs 17 Hz Compliance, Cms 0.43 mm/N Moving mass incl. air, Mms 205 g Maximum mechanical cone excursion, Xmech ±17 mm Mechanical loss, Rms 3.0 kg/s Mechanical Q-factor, Qms 7.3 Equivalent volume, Vas 60 liters Net weight 1.45 kg T/S parameters measured on drive units that are broken in.