Rythmik's spec on their 18" sub with an MSRP of $1700.
Driver
DS1820 18" high excursion with custom sensing coil
Driver materials One piece black anodized dish aluminum with rubber surround
Cast aluminum basket
Multiple aluminum flux de-modulation shorting rings
Amplifier 900W RMS Hypex class-D patented servo controlled
Dimensions 21"(W) x 33" (H )x 22"(D) - (23" D with grille and heatsink)
Shipping Weight 180 lbs
Frequency Response 12 - 200 Hz (-4db@12hz) with LFE input
12 - 90 Hz (-4db@12hz) with LINE IN input
Multi-tune 16hz (3 port) and 12.5hz (2 port)
Crossover slope Selectable 12 or 24 dB / octave (PEQ)
Crossover range (Low pass) 25 - 100 Hz
Rumble Filter (High pass ) 12 Hz 18 dB / octave (defeatable, recommended for high SPL playback)
Phase adjustment 0 - 180 degrees continuously variable
Bass damping factor settings high (Q=0.5), med (Q=0.7), and low (Q=1.1)
Finishes Available in black matte paint or black oak vinyl
Warranty 5 years warranty on driver and 3years on electronics
45 day home trial with customer paying one-way return shipping
http://www.rythmikaudio.com/FV18_specs.html