Floorstanding loudspeakers — ATC SCM40

The SCM40 is a floor-standing passive speaker with three drivers from the ATC hi-fi catalogue and the lowest-cost three-way model the company offers. The current curved-cabinet version replaced a 2007 design of the same name and was priced at 3,275 GBP per pair in the UK and 7,999 USD per pair in the US. ATC gives it a 6-year warranty, of which the basic term is two years, extended to six once the owner registers the product.

Key specs that matter

Inside are a 25 mm neodymium soft dome tweeter, a 75 mm soft dome midrange and a 164 mm SC bass unit - with crossover points at 380 Hz and 3.5 kHz. The response is rated at 48 Hz to 22 kHz at the -6 dB points, and pairs are matched within 0.5 dB. Sensitivity is 85 dB at 1 W and 1 m, nominal impedance is 8 ohm and maximum SPL reaches 112 dB. Coherent dispersion is specified at plus or minus 80 degrees horizontally and plus or minus 10 degrees vertically. Including the foot plinth the speaker stands 980 mm tall, 370 mm wide and 305 mm deep, with the spikes fitted it gains 25 mm in height, and its grille adds 34 mm of depth. Each cabinet weighs 31 kg.

Engineering and use context

ATC built the enclosure as a fully sealed infinite-baffle design in MDF, extensively braced, with gently curved side walls and a front baffle wider than the rear. The SH25-76 tweeter uses a dual suspension, runs without ferrofluid and sits behind a precision-machined 5.5 mm alloy waveguide, with a 1.5 tesla neodymium magnet driving a short edge-wound coil. The midrange is the SM75-150, whose hand-doped acrylic dome is carried on a dual suspension of its own. Below the lower crossover point a long-throw woofer takes over, built with a hand-coated carbon-paper cone, a short voice coil in a long magnetic gap and a large optimised motor. The metal grille attaches magnetically, and the cabinet rests on an MDF plinth fitted with four M8 x 1.25 mm spikes. Finish choices are Cherry or Black Ash wood veneer, plus two paints, Satin White and Satin Black.

Pairing

ATC recommends amplification between 75 and 300 W per channel. The impedance curve is designed to stay flat so the load is easy on the amplifier, and the rear binding posts take 4 mm plugs and support tri-wiring, allowing separate cable runs to the bass, midrange and treble sections.

Alternatives

The ATC EL50 Anniversary is the brand's active floor-standing model, made in a run of 50 pairs, with on-board amplifier channels of 200 W, 100 W and 50 W per driver.