ATC SCM7 MkIII Bookshelf Speaker Review

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ATC SCM7 MkIII Bookshelf Speaker Review

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ATC-7-speaker_no-grill-650x1024.pngATC originally made its mark in professional recording studios. In 1974 Billy Woodman created ATC and began manufacturing a 12-inch driver that could handle more power and produce less distortion at higher SPL levels than existing drivers. ATC soon followed the 12-inch driver with a soft dome midrange driver in 1976, and then complete speaker systems soon thereafter. During the intervening 40 years, ATC has expanded into powered and active speakers, as well as standalone electronics.

Today's review will concentrate on one of ATC's least expensive and smallest consumer speakers, the SCM7 ($1,499/pair). This two-way system was designed for nearfield and small-room listening, and it combines ATC's legendary ability to play loudly with low distortion with a small footprint that can fit into a tight space easily. Given that consumers have more choices in small monitor speakers than any other speaker category, the ATC SCM7 faces some tough competition. Let's see how it fares.

Additional Resources

The SCM7 isn't a new model; this third version, named the mark III, has been completely redesigned. It features ATC's new SH25-76 25mm soft dome tweeter that uses a special dual suspension system that suppresses rocking modes, as well as a short edge-wound voice coil in a long narrow magnetic gap to eliminate the need for ferrofluids for cooling. With a 15,000 gauss (1.5 tesla) neodymium magnet, a precision-machined 5.5mm rigid alloy waveguide, and a heat-treated top plate that increases heat dissipation, the SH25-76 tweeter delivers (according to ATC) "optimum dispersion, flat on-axis frequency response, and resonance-free operation." The SCM7's midrange/woofer is 125mm (five inches) in diameter and uses a 45mm (two-inch) soft dome with a 3.5kg magnet system and a 45mm flat-wire voice coil. The magnet system and carefully weighted and doped fabric cone contribute to the driver's overall performance, which is aimed at creating a speaker with excellent horizontal dispersion, wide bandwidth response, and convincing bass response.

The biggest physical difference between the second- and third-generation SCM7 is its cabinet shape. Instead of the fairly standard box used by the mark II, the mark III's cabinet has curved sides to reduce internal resonances and increase overall cabinet rigidity. Another external difference is the mark III's magnetic grill cover attachments instead of the old-style, push-in kind. This makes for a much cleaner look when the grills are removed as well as far quicker and easier attachment and removal. The back of the SCM7 has two pairs of five-way binding posts that can be bi-wired if you wish.

Unlike many small monitors that rely on a port or vent to augment their bass response, the SCM7 is a sealed cabinet. The advantage of not using a port is that it eliminates the group delay issues and phase anomalies that a port creates. This makes it much easier to blend the SCM7 seamlessly with a subwoofer. Instead of producing a mid-bass hump, the SCM7's bass rolls off smoothly with substantial output down to 70 Hz.

The Hookup
SB45-125SCweb-res-140x93.jpgDuring most of the review, the ATC SCM7 speakers were situated in my nearfield desktop system because that is their intended primary application. ATC has a whole slew of larger speakers, such as their SCM11, that are better suited for room-based applications (unless your room is very small). In order to get the speakers set up so that my ears were on a horizontal plane between the tweeter and midrange/woofer, I used a pair of closed-cell, high-density "stands" that I made, as well as a pair of Ultimate Support adjustable speaker platforms to raise and angle the speakers so they were parallel with each other. After trying them at various angles varying from pointing straight forward to a 45-degree angle, I opted for about a 40 degrees of angle (according to the Genelec Speaker Angle app).

I used several different power amplifiers with the ATC SCM7 speakers, including the Wyred4Sound mAMP, the April Music Eximus S1, and the little Olasonic Nano-UA1 integrated amplifier. Even though the SCM7 speakers are only rated at an 84dB efficiency and the Olasonic only puts out 26 watts into four ohms, this combination generated adequate volume levels on commercial material for a desktop or even a small-room environment. On my own recordings, which have a lower overall volume level than most commercial releases, at times I longed for more output from this combination, especially during FFF (triple forte) passages, when the Olasonic just ran out of juice.

Although the SCM7 speakers had adequate bass output down to 70 Hz in my desktop system, if you require further bass extension, the use of a subwoofer is recommended. I coupled the SCM7 speakers with a Velodyne DD10+ subwoofer. Crossing over from the SCM7 speakers to the subwoofer at 70 Hz delivered a smooth transition from the monitors to the subwoofer. For part of the review period, I used the crossover to reduce the bass sent to the SCM7s, but most of the time I let the SCM7s bass roll off naturally with no additional bass attenuation. Obviously, one way to increase the SCM7's power handling would be to use a crossover to reduce the bass directed to the SCM7s, but this can also reduce transparency because of the additional circuitry and cabling. Also, because the SCM7 speakers have such extended power handling, the need to shield them from having to cope with low bass frequencies is reduced, especially when compared with other similarly sized small monitors.


Click on over to page 2 for the Performance, the downside, the competition and comparisons, and the conclusion . . .

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