ATC SCM19A Loudspeaker


Equipment report
ATC SCM19A Loudspeaker

This review might not sit well with some of my audiophile friends. I’m referring to a large and ardent band of devotees who enjoy the “chase” in the high end—those who make every audio-system component choice with the deliberation of a chess grandmaster contemplating a critical move, weighing each option, mod, or upgrade and scrutinizing the results for the smallest shred of improvement. Indeed, this open-system approach is a big part of the hobby, and I don’t begrudge anyone his level of enthusiasm. It’s what we do. Truth be told, once upon a time I would have included myself in this group. Back then, the very idea of a semi-closed system that a bi-amplified loudspeaker like the ATC SCM19A represents would have been heretical to my high-end aspirations. But, as they say, that was then.

Here’s the backstory: I’ve owned a couple versions (passives) of the ATC SCM20SL over the years. I recently reviewed its successor, the SCM19 (Issue 245), which proved to be a better overall speaker than my SCM20’s in most every way. The idea of an active loudspeaker intrigued me but what really sparked my interest was an ATC demonstration of active versus passive at CES 2015. It was a shootout between the SCM40 and its active cousin the SCM40A—otherwise identical three-way, acoustic-suspension floorstanders. The latter, however, was equipped with an internal electronic crossover splitting the signal into tri-amplified power. The former was the traditional passive design and received comparable power from ATC amplifiers and traditional speaker cabling. The differences were startling. Improved imaging, a vastly greater sense of dimensionality and immersion, and a level of low-frequency control that said to me in no uncertain terms “there is no going back.” When I was informed that ATC had plans for an active version of the SCM19, I told them I was all in. Would the differences I experienced at the CES demo translate into my own listening room with the two-way version?

A brief history: ATC of England begin producing custom transducers for the professional sound market in 1974. Active monitors and electronics soon followed. Since then it has developed a worldwide reputation not only for speakers that will play loudly but also for the bulletproof reliability the pro market counts on. The consumer market has been a tougher reach for ATC in part because it’s a company that doesn’t engage in smoke and mirrors or eye-catching derring-do. Rather it lets its products do the talking. Thus its look and cosmetics speak to solidity and permanence. Fit and finish are always seamless but not indulgent. However, with the advent of the new Entry Series that comprises three décor-friendly, passive, stand-mount models and a trio of floorstanders (two are active), plus a flurry of excellent reviews and word-of-mouth, ATC seems to be gaining a well-deserved, consumer-based foothold in North America.

The SCM19A is a two-way, acoustic-suspension floorstander but it’s probably more accurate to think of it as the standard SCM19 fused atop an extended cabinet designed to house the electronic crossover and bi-amplification. Therefore the actual internal volume that the transducers “see” is identical, although—and this is of no small importance—the passive crossover network components have been removed and thus are no longer subject to vibration from the internal back wave of the drivers. To increase floor stability for the slender tower enclosure, ATC provides a wooden plinth “outrigger” stabilizer with threaded floor spikes. The ATC-engineered Class AB MOSFET amplification is installed in the bottom half of the tower. The biamplified system powers the mid/bass drive with 150W, and sends 32W to the tweeter. The second-order crossover slope at 2.5kHz incorporates phase compensation. Keep in mind that because it is an active design, the frequency spectrum is split by the crossover at line-level prior to amplification. Consequently, all this power is available to the drivers without the significant power losses of a passive network. Heavy aluminum heatsinks rise vertically above the power button, balanced input, and IEC plug.

The SCM19A tweeter (model SH25-76 in the ATC catalog) is a 25mm soft dome. It’s a short-coil, long-gap, dual-suspension design that mirrors ATC’s highly respected 3" soft dome midrange. This design enables the use of a narrow magnetic gap and negates the requirement for ferrofluid—and the potential negative effect of the fluid drying out over time. The tweeter is set in a resonance-free, machined-alloy waveguide that’s been designed to optimize dispersion and allow for the flattest possible on-axis frequency response. Midrange and bass frequencies are handled by ATC’s 6.5" Super Linear mid/bass unit—a driver recognizable by its sophisticated diaphragm structure that integrates the profile of a traditional cone with that of a 75mm soft dome. Per ATC tradition, the mid/woof features a short coil in a long gap, a massive ceramic magnet, and a long-throw suspension for linearity at extreme dynamic levels. The ultra-rigid basket construction appears sturdy enough to support an eighteen-wheeler. Per ATC practice these drivers have been designed and manufactured in-house. They are not off-the-shelf items from a third party.

Once plugged in and warmed up for about a half an hour or so, the SCM19A resembles the passive SCM19 in tonal balance and overall sonics, which is to say it is highly neutral through the midrange and presence range. There’s a warmer tinge to its overall character thanks to its weighty lower mids and upper bass—major pluses in a compact two-way. There’s excellent high-frequency extension and air to keep winds and brass satisfied. For vocal articulation, sibilance is naturalistic but never to the point where it tips over into snippy edginess.

Far and away its biggest asset (and this was also true of the SCM19) remains its fast, dynamic, and transparent midrange—one that anchors images, from vocals to violins, and establishes their palpable presence in the room. Whether it’s the gravel and grit of a Tom Waits’ vocal or the soothing, silvery soprano of Alison Krauss, the SCM19A is a “voice” speaker that is addictive in its verisimilitude. Its resolution of internal harmonies like the Buckingham/McVie backing vocals to Stevie Nicks’ lead during “Gold Dust Woman” is definitive in the way it reproduces each vocal nuance. Particular credit goes to the newly designed tweeter, which integrates perfectly with the midrange and bass rather than sounding like a separate sound source. The result is a near-ideal point-source coherence matched by transducers that seemingly speak with one harmonious voice. This trait can be heard with every piano note, or the draw of a violin bow across an E string.