From the linked page:
"The New Larger Subwoofer, in its restyled round-corner lowboy cabinet, is the lowbass section of our renowned Super Tower IIa/R tower (active 30 and 38 cm polycone woofers (12" and 15"), slot-loaded 38cm passive (15")) in an 226 l, 63 kg (138 lbs) light or dark oak veneered enclosure made from 25 mm (1") thick MDF. It is designed for the audiophile desiring the ultimate in separate lowbass modules without the expense involved purchasing the best competitive units of other manufacture. Distortion (0.5% / 1W), bandwidth (-3 dB at 17 Hz), sensitivity (92 dB/1W), and maximum undistorted output levels (115 dB/1m plus at 20 Hz) are unsurpassed and not even approached by all but one or two very costly competitors. Press comment on the lowbass performance of the STIIa/R include: "World Class" (High Fidelity Ap 85); "Awesome...left bruises on my abdomen" (Hifi News & Record Review, England, Ap 85); "Excellent dynamic response and overall accuracy...superb power handling capabilities...has an ability to show that bass can provide the listener with important sound-stage information" (Audio, Aug 85). "