Floorstanding loudspeakers — Fischer & Fischer SN/SL 770.1 AMT

The SN/SL 770.1 AMT is a passive floor-standing loudspeaker with a cabinet of natural slate, built by Fischer & Fischer, a company owned by Thomas Fischer and based at Stationsweg 8a in Schmallenberg-Dorlar, Germany. The maker says its products have been made for 45 years. The double name refers to two surface versions of the same design - SN keeps the natural slate surface, while SL receives a polish and a lacquer finish, available on request in RAL colours or in car paint shades.

Key specs that matter

Six drivers share the work. Two 220 mm Fischer & Fischer cones act as subwoofer units, a third 220 mm cone handles the bass section, and two 180 mm cones cover the midrange. The two larger groups use a sandwich membrane of carbon paper and foam, while the midrange units combine carbonised paper with a carbon foil layer and carry an aluminium phase plug. High frequencies reach an Air Motion Transformer, a unit Mundorf builds to a special custom order. The quoted response runs from 24 Hz to 27,000 Hz within 3 dB, nominal impedance is 4 ohm, sensitivity is 92.5 dB at 1 W and 1 m, and the maximum acoustic pressure is given as 115 dB.

Engineering and use context

Fischer & Fischer builds the enclosure in three parts from slate plates 20 and 23 mm thick, a material the maker chose for its low resonance, and the enclosure works on the bass reflex principle. The filters are of first and second order and are corrected for both phase and impedance. The slate body alone measures 1550 mm in height, 275 mm in width and 420 mm in depth. It stands on a levelling floor system of aluminium, which brings the overall size to 1610 x 380 x 475 mm, and the complete speaker weighs 159 kg.

Pairing

Connection is by tri-wiring terminals rated at 63 A and rhodium plated, supplied with bridges of pure silver for owners who run a single cable. With the bridges removed, the three terminal pairs let the subwoofer, bass and upper sections be driven from separate amplifier channels or fed by three independent cable runs from one amplifier. A partner amplifier with good current reserves into this slate tower's low load is the sensible choice, while the high sensitivity means that very high output power is not a precondition for reaching normal listening levels.

Alternatives

The Fischer & Fischer SN/SL 1000.1 AMT is the larger slate floorstander of the range, with two 260 mm subwoofer cones, two bass cones and a weight of 283 kg.