ATC SCM50 ASLT Loudspeaker

Active Alternative

Equipment report
ATC SCM50 ASLT Loudspeaker

Audiophiles and active loudspeakers have had, shall we say, an uneasy relationship over the years. The squabble goes something like this: Active speakers (defined here as speakers equipped with on-board amplifiers and electronic crossovers) are the outsiders, creations of and for the recording studio—only pros need apply. The argument continues that while active designs tout tonal accuracy, they are just as often described as amusical and clinical-sounding beasts geared to play all day and night at ear-splitting levels.

Some of these generalizations contain seeds of truth, but many are mere clichés from a bygone era. Really, the only serious gripe that is still valid is that the “active” approach is antithetical to the audiophile norm—a culture of discrete-component system-building, with the freedom to choose any product in the electronics chain and not be wedded to it for life.

However, time, tastes, and technology have narrowed, if not mended, the great divide between the passive and active camps. Today, for example, there are countless hybrid models with powered bass transducers (Vandersteen, MartinLogan, GoldenEar). Wireless and DSP have also opened up fully active options for designers (Linn, Dali, Elac, KEF, Dynaudio). And I don’t need to remind anyone about the popularity of powered/DSP subwoofers, right? Suddenly plugging a loudspeaker into a wall outlet doesn’t seem like such an act of heresy.

One certainly doesn’t need to convince ATC of England of this. The company has been in this game since its founding in 1974. Acoustic Transducer Company (ATC for short) actually began by concentrating its efforts on the design and in-house manufacture of custom transducers for the pro-sound market. By the end of that decade it had started producing professional active monitors, adding electronics and amp packs soon thereafter, and then, finally, consumer-oriented products.

The SCM50 ASLT (active super linear tower) reviewed here has a particularly long and distinguished lineage within ATC, one that dates back to the mid-1980s. The original SCM50A came into being as the result of a request by Danish Radio for a compact monitor speaker for its broadcast trucks. Subsequently adopted by recording studios, it has steadily evolved with the passage of time. I’ve encountered ATC in recording studios as recently as a few years ago when I visited the late Doug Sax at The Mastering Lab.

The SCM50 ASLT is a three-way floorstander that tops out at around 40" in height and a foot in width, and thanks to its amp-packs extends rearward a full 18". For ATC-watchers, this model is the tower version of the famed SCM50 ASL Pro Monitor, which still graces many a studio today. The look is that of a traditional British loudspeaker—boxy, understated, yet handsomely brutish. The midrange and tweeter drivers are vertically offset relative to the woofer, reducing the effects of cabinet diffraction and permitting the user to orient the speaker according to taste—drivers inboard tend to pinpoint images and add depth to the musical stage, while outboard adds a bit more width. As described by Ben Lilly, Engineering Applications/Sales Manager, “The cabinet is braced and damped with 18mm MDF. Damping panels are a multi-layer bitumen-type product glued and stapled to the cabinet’s inner face. The baffle is 25mm thick. We use a thicker, heavier, more inert front baffle on many of our products because this panel faces the listener—panel resonances from this area are more audible.” There’s no scrimping on cabinet fasteners, either. The baffle is secured with fourteen Allen-type bolts, the woofer alone uses eight more. Should you wish to disguise these details, the grille frame is cleverly designed to snuggle around the edges of the projecting front baffle for low diffraction. Standard finishes include satin cherry, oak, walnut, and black ash. I found the overall fit and finish excellent—it speaks to solidity and permanence.

This is a tri-amplified loudspeaker that delivers 200W to the woofer, 100W to the midrange, and 50W to the tweeter. The Class AB MOSFET amplifiers mounted on the rear panel are augmented with a bank of heat sinks and large grab handles. The SCM50 accepts only balanced XLR inputs and the included power cords are detachable. In operation, the amps are dead silent.

The heart of every loudspeaker is its transducers. To ensure that heart is beating, ATC doesn’t leave its designs to third-party manufacturers. Each driver is a bespoke ATC unit, engineered and manufactured in its venerable factory in Stroud, England. Most recently, and after many years of development, ATC introduced its own 1" soft-dome tweeter, model SH25-76S S. It’s a non-ferrofluid, double-suspension design in a shallow waveguide. The 9" woofer is one of ATC’s top-drawer Super Linear models, purposefully engineered to reduce eddy currents and lower harmonic distortion. Easily the jewel in the crown of ATC transducers is the 75mm soft-dome midrange, model SM75-150S. Developed in the 1980s, it’s a dual-suspension design for better diaphragm control, greater heat dissipation, and higher power handling. Equipped with a huge three-inch voice coil, it’s renowned for its power handling and lack of compression. Per ATC practice it uses a short coil operating in a long magnetic gap (aka, it is underhung). This particular model is the pro “S” or super-version, which offers a larger magnet for increased sensitivity (92dB/1W/1m), extended upper-mid response, and lower distortion. To further extend response it is mounted in a “phase correction flange.” Like every driver in the ATC family, it is a massively built transducer that tips the scales at nearly twenty pounds—yes, you read that correctly. For one driver. The crossover is a fourth-order Linkwitz-Riley type, with hinge points at 380Hz and 3.5kHz.

Admittedly I felt an instant familiarity with these speakers. Truth be told, I’ve owned ATC passive two-ways like the SCM20SL for years. Also, I recently reviewed the excellent    SCM19A, an active two-way floorstander. Sonically, there is a signature design philosophy that ATC and its founder Billy Woodman have hewed to since the firm’s inception. It begins with the “instrument of the orchestra,” the piano. For a product to reproduce a piano’s full range of expressiveness and sustain, of harmonic authenticity and dynamic explosiveness, it must be capable of a very high level of musical truth. A pianist himself, Woodman (and his team) use the sound of a piano to weigh every ATC design.