Bookshelf Speakers — ATC SCM19

The SCM19 is a stand-mounted passive loudspeaker with two drivers, part of the Entry Series of ATC, the British maker that builds its own drive units and has worked in both studio and domestic audio since the 1970s. It sits above the smaller SCM7 in that series and is hand-assembled at the company's site near Stroud in Gloucestershire. The design is a sealed box rather than a reflex one, and ATC offers it in cherry or black ash veneer as well as satin black or satin white paint.

Key specs that matter

Treble above 2.5 kHz is handled by a neodymium-powered 25 mm soft dome, and a 150 mm SL mid/bass unit covers everything below. The -6 dB response runs from 54 Hz to 22 kHz. Sensitivity is 85 dB for 1 W at 1 m, nominal impedance is 8 ohm, and the maximum SPL is 108 dB. Speakers are paired to within 0.5 dB, and dispersion is given as plus or minus 80 degrees horizontally and plus or minus 10 degrees vertically, both coherent. The cabinet is 438 mm high, 265 mm wide and 300 mm deep, with the grille adding 34 mm to the depth, and each speaker weighs 17.8 kg. Connection is through binding posts that take 4 mm plugs and allow bi-wiring.

Engineering and use context

ATC's own tweeter design is mounted behind a waveguide machined from precision alloy, and both drivers have doped-fabric diaphragms. The mid/bass driver uses a dual-profile diaphragm, in which a conventional cone surrounds an integral 75 mm soft dome, and its voice coil is short and sits in a long magnetic gap. That motor assembly weighs 9 kg and uses a ceramic magnet, while the flat-wire coil is wound by hand at the factory. The cone hangs on a long-throw suspension. The MDF cabinet has curved side panels that arch toward the back panel, a shape chosen to reduce internal standing waves, and the grille attaches with hidden magnets. ATC also stresses a flat impedance curve, which makes the load easy for an amplifier to handle. Like other ATC products, the SCM19 carries a 6-year warranty.

Pairing

ATC recommends amplifiers rated from 75 to 300 W. With a sensitivity in the mid-80s and a sealed bass alignment, an amplifier toward the top of that range is the more sensible match than one near the bottom, and the split terminals make it possible to use separate cable runs or two amplifier channels for the mid/bass unit and the tweeter.

Alternatives

The ATC SCM7 is the compact Entry Series stand-mount, with a 125 mm mid/bass unit, 84 dB sensitivity and a 300 x 174 x 215 mm cabinet.