Test speaker system ATC SCM100 ASL: active professionals

The ATC SCM100 ASL active loudspeakers bring studio-quality reproduction to the home and are among the best value speakers in their category, especially considering the fact that fully matched Tri-Amping power amplifiers, “wired” to the speakers, are already included. The only drawback is the not very attractive, angular design of the loudspeakers, which can scare away fans of LifeStyle.

The test: Denis Goncharov, Consumer magazine. Video&Audio

Acoustic system ATC SCM100 ASL

CONSTRUCTION

The British ATC Acoustic Transducer Company was founded in 1974 by the Australian engineer Billy Woodman. Originally headquartered in the suburbs of London, the company moved to a quieter, more tranquil location in the town of Stroud in pastoral Gloucestershire in 1985.

ATC brand is more famous in the world of professional acoustics and enjoys the indisputable authority in this environment. Its customers include the BBC, CBS, EMI, Sony DVD and SACD Mastering studios in New York, Pioneer Mastering, Real World, Gateway Mastering, Pink Floyd, Naxos and TelArc, the Todd AO, Paramount Pictures, Warner Brothers and many others. The number of companies-users of ATC equipment has long ago exceeded a thousand. Since recently, in addition to professional monitors the company releases “home” audio equipment: active speakers and their passive analogues, amplifiers. But the company’s “hobbyhorse” is considered to be active acoustics, which best embodies the principles of Woodman.

As a young engineer who had just moved to England, Woodman set himself the ambitious goal of combining the natural sound quality of the best hi-fi speakers of the time with the wide dynamic range of horn speakers. Woodman also strived to design the speaker with a wide dispersion pattern to give the listener a wide range of high quality stereo effects.

None of the loudspeakers on the market at the time conformed to such requirements: British Rogers, for example, which served as BBC court monitors, had natural sound but a limited dynamic range, while the American speakers of those years had luxurious dynamics but tolerated some tonal liberties.

So Woodman had to do some research of his own to realize that dream and, after several years of work, he built his own midrange speaker, complete with a dome diaphragm made of paper with a viscous coating that improves the damping properties of the cone. To increase the sensitivity of the loudspeaker and to control its radiation pattern the paper dome is inserted into a shallow horn. Today, Woodman’s horn-dome midrange is considered one of the best in the world, and many manufacturers are even trying to copy his design.

All parts of its speakers, with the exception of tweeters and cabinets, are manufactured in-house by ATC. The speaker cabinets are made from ATC patterns by British furniture companies and the tweeters are bought from renowned firms such as Vifa and Seas. Before they go into stock, ATC loudspeakers undergo a stern inspection: they are “swept” with a signal amplitude of 20V. Once they pass this test, the loudspeakers can safely operate in any studio or home theater system. In each pair of loudspeakers ATC sound parameters are maintained with high accuracy: for example, the frequency response is within 0,5 dB.

We tested the active speakers ATC SCM100ASL in the floor-standing version these models also have passive versions and active, but designed for mounting on low racks. Traditionally PBX speakers are built in strictly rectangular, solid MDF cabinets, fastened inside with numerous cable ties. The front of the speakers is additionally stiffened by a several centimeters thick wooden plate, into which the speakers are inserted – there are no decorative gadgets, the entire structure is reliable and extremely functional.

As far as we know, the designers of ATC departed from this “classic” design only once, succumbing to the “perverse” influence of fashion, they have produced a model EL150 SLP with oval cabinets. The SCM100ASL cabinet is placed on a low pedestal below, barely looking out from the main cabinet. More speaker colors are available year by year, and the SCM100ASL is available in Yew, Cherry, Walnut and Rosewood veneers or painted black.

The speakers are equipped with a Seas Excel series tweeter equipped with a 25mm dome, silver voice coil and dual neodymium magnet system. From 3.5kHz the tweeter takes over from Woodman’s 75mm diaphragm horn dome MF driver. The driver uses a 75mm 3.5mm voice coil, suspended in a 5mm magnetic gap. The coil is surrounded by a massive 7.5kg magnet system.

The clearance is a hundredth of an inch, making it possible to cool the coil by the magnet itself. ATC traditionally uses speakers with a short voice coil and a long magnetic gap – this combination ensures that the coil is always in the linear field, even at maximum volume. As a result the tonal balance of the ATC loudspeakers is very little affected by the level of sound emitted, a property that is essential in the professional studio, but is also useful in the home system.

The SCM100 ASL has a 314mm paper diaphragm driver for frequencies under 380Hz. The driver uses ATC’s patented SLM Super Liner Magnet technology developed in 1986. The technology is designed to eliminate the eddy currents generated in the motor, which occur in the surface layer of the metal parts of the driver and cause non-linear sound distortions.

To suppress this undesirable effect, ATC replaced the thin layer of the magnet pole tip and surrounding areas with a special SLM material, which is electrically insulating but permeable to magnetic fields. The SLM has a complicated structure: there are iron fines suspended in the polymer and a volume of material interspersed with oxide layers. As a result, the coil is not shielded from the magnetic field, but the eddy currents in the SLM volume are suppressed.

Each speaker in the SCM100 ASL is served by its own amplifier, the whole kit is called an Ampack and has a total power of 400 watts: 50 watts for the tweeter, 100 watts for the midrange and 200 watts for the midwoofer. The amplifier circuits in the ATC are designed by Woodman’s companion, Tim Isaac. He built his first prototype of three separate amplifiers for each channel in 1985., since then, the company’s engineering staff has regularly refined the circuitry.

Each monoblock amplifier is optimized to work with its dedicated speaker, and each monoblock has an isolated power system, although the amplifiers are assembled on a single chassis to save space. All ATC amplifiers are MOSFET based and operate in pure Class A up to 2/3 power.

The SCM100 ASL crossover uses proprietary 4th order Linquitz-Riley crossover filters, also designed by Isaac. There is precise analogue phase correction at the band split frequencies, so the ATS speakers have no equalisation systems or built-in DSP, everything that is needed is already done by the engineers at the active crossover assembly stage.

Connection to the preamplifier or signal source is via XLR connectors. The fully balanced input of the integrated amplifier allows cables of up to 50m length to be connected to the speaker, although this feature is hardly useful in domestic environments.

SOUND

The SCM100 ASL loudspeakers sound with pinpoint accuracy, with careful handling of timbres and overtones, and their natural, neutral character is maintained throughout the entire range, from the lowest octave to the extreme treble. In addition to all other advantages, Englishmen have accurate tonal balance and a good dynamic range of sound, the speakers realistically convey fine dynamic contrasts and microamplitude information, while they do not tend to artificially emphasize the nuances of the recording – a weakness, which allow themselves other studio monitors.

However, this does not mean that the speakers will forgive the recording any mistakes – poor track moments will immediately come to light with full clarity. I liked that the dynamics and attack of sound is maintained not only in HF and MF, bass is not inferior to the middle in terms of speed, intelligibility, enviable sound articulation slowly begins to spoil only in the lower octave.

The rare gift of SCM100 ASL speakers is their ability to intelligently build up a scene at a low volume and then hold a focused image already at any input power. Musicians’ positions are precisely reproduced even in orchestral compositions, the scene is not impaired either on the edges or in the background, bass groups are very clearly shown. Show concert hall reverb – no problem, so on orchestral recordings performed by SCM100 ASL musicians never look suspended in space, the listener always gets information about the size of the room where the recording took place.

Another advantage of the speakers, in addition to a very wide and deep, transparent scene – a total detachment of the stereo image from the speakers themselves, they seem to vanish into thin air, the listener can freely move around the room without risking to go beyond the zone of the correct stereo effect. Almost from any position you can “see” all the same contrasting holographic picture.

The SCM100 ASL is very difficult to find the disadvantages, in fact, there are none at all. But it seemed that this system demonstrated very good, but not the extreme macrodynamics of sound at the edges of the spectrum: the system tends to slightly reduce the amplitude of the drum beats or the sharpness of the hi-hat sound.

PRICE

Depends on the finish, the average cost of 685,000 Dollars.

MEASUREMENTS

The SCM100 ASL loudspeakers exhibit excellent linearity in the 40-20kHz operating range with a ± 2.5dB non-uniformity.

Angular uniformity is also excellent, with a sensitivity curve very close to the axis in the 30° direction, with minimal dips in the top octave and near the top of the crossover. The lower limit of ± 3 dB was 34 Hz.

Graph of the AFC measured on-axis and at 30 degrees

The editors of the Consumer Video & Audio magazine would like to thank Nirovision

and Fostergroup salon m. Krasnye Vorota for their help in making this test.