Woofers have new surrounds, crossovers had electrolytic capacitors replaced (original caps included), new grill cloth, new modern binding posts, original ADS badges. These are legendary speakers, based on German designs by Braun. Imported, and improved upon by NASA engineer, audio legend Godehard Guenther. Frequency Response:  40 - 23,000 Hz, ±3 dB;  25 - 30,000 Hz, ±5 dB Impedance:  6 Ω (nominal);  4 Ω (minimum) Efficiency:  93 dB SPL with 2,8 V RMS Crossover:  12 dB/oct at 550 Hz and 4,000 Hz Power Rating:  75 Watts (nominal),  150 Watts (max. Peak program) Recommended Amplifier Power:  15 Watts minimum - 150 Watts maximum Dimensions (H x W x D):  21⁵⁄₈" x 12¼" x 10½" Weight:  Approx. 35 lbs (16 kg) Cabinet:  Select natural walnut over extra-high-density particle board, solid walnut edge inserts