Well I am the proud owner of a JBL-PRO Cinema Subwoofer in my room it is flat at 25hz and this subwoofer really shakes my home, I am using an Adcom 555 in bridge mode to power this beast.
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4641
Subwoofer 4641 Specification Sheet

Single 460 mm (18 in) High Power Subwoofer.
Approved by Lucasfilm, Ltd. for THX® system installations.





Low Frequency Driver: 2241H
Frequency Range: 25 Hz - 500 Hz (-10 dB)
Power Capacity (Continuous Pink Noise): 600 Watts
Power Capacity (Continuous Program): 1200 Watts
Sensitivity: 98 dB SPL (1W, 1m, 3.3ft.)
Crossover Frequency: 80-150 Hz recommended
Nominal Impedance: 8 Ohms
Dimensions (HxWxD): 1010 x 674 x 450 mm (39 3/4 x 26 1/2 x 17 3/4 in)
Net Weight: 60 kg (131 lb)