When our editor, Dave Thomas asked me if I would be interested in reviewing a small active loudspeaker and preamp system, I have to admit to being a little hesitant. My hesitation stemmed from the fact that I had been used to listening to monolithic electrostatic speaker systems from Sound Lab and had become a little jaded toward dynamic speakers. Boy, am I glad I took this assignment because the system was the ATC SCM10A-2 loudspeaker and CA2 preamp. I’ll cut to the chase and say that this has been one thoroughly enjoyable experience. To find out why, please read on.

Dave put me in contact with Chris Barry, owner of High Fidelity Systems in Chicago, to pick up the ATC equipment. When I arrived at the store, Chris enthusiastically invited me to listen to a couple of other ATC speaker systems and I was impressed with what I heard. Hopefully the opportunity will arise in the future to review other ATC speakers.

It has been a long time since I have really listened to an active speaker system. The first time was more than 25 years ago when a professor friend of mine came over from England to teach. He had a system consisting of a Linn LP12, Meridian preamplifier and tuner, and an unknown active tri-amplified speaker system. The speakers were without question some the finest sounding that I had heard at that time. Their sound was transparent, dynamic, and a joy to listen to. The ATC SCM10A-2 loudspeakers have similar characteristics but to my surprise, have an even more refined sound.

ATC History
ATC stands for Acoustic Transducer Company. Billy Woodman, an acoustic engineer and musician, formed ATC in 1974 to design and manufacture custom high-performance drive units for the professional speaker market. The woofers and soft dome midrange are known for their exceptional power handling, low distortion and high output. This is a result of innovative design and manufacturing to the highest standards. The company evolved from just making drive units to producing complete state-of-the-art speaker systems and electronics for professional and home use.

Active Speakers Systems
Active speaker systems, for those of you who are not familiar, are basically speakers that contain the power amplifier(s) within the speaker enclosure. Examples that come readily to mind are powered subwoofers and personal computer add-on speakers which are driven from the output of a sound card. Active speakers are popular with the mass market “plug and play” crowd, but what about the serious audiophile and music lover? The vast majority of audiophile systems do not incorporate active speakers. Why? Well, the reasons are many and varied. One reason could be that it would take all the fun (or headache) out of trying to come up with the magic speaker, cable, and power amplifier combination that will yield audio nirvana. Another could be that audiophiles have not experienced an active speaker that met their standards for serious music reproduction. There aren’t that many manufacturers of high-end active speakers in the first place.

Active speakers have the potential to out perform their passive counterparts if they are well designed. In an active speaker a line level signal is fed to the speaker which passes first through an electronic crossover which divides the audio frequency range into parts. For example, let us consider a three-way system. The low frequencies would be sent to the amplifier which drives the woofer, the middle frequencies to the amplifier that drives the midrange, and the high frequencies to the amplifier that drives the tweeter. Notice that the amplifier delivers power directly to the driver, be it a woofer, midrange, or tweeter. This is one of the keys to superior performance. The power amplifier has complete control over the driver. There is no crossover network between the amplifier and the driver. Gone are the large inductors, capacitors, and resistors that comprise the crossover network in a passive speaker system. This gives the designer the freedom to design an amplifier that is optimized for a given driver resulting in much higher performance. The crossover network in an active system is done electronically (active filters) meaning there are no inductors, the capacitors are small value and the resistors are low wattage. This gives the designer another advantage in that superior precision parts can be used. Now the only sonically limiting factor is the quality of the amplifiers to which the precision parts are connected to form the active filters.

The ideal active speaker is one in which the electronic crossover and power amplifiers are sonically transparent, the finest drivers are used, the speaker enclosure is non-resonant, and everything is synergistically optimized to produce phase coherent, uncolored sound. This basically describes the ATC SCM10A-2.

Product Description
The ATC SCM10A-2 is a two-way design that incorporates a 5” mid/bass driver and a 1” soft dome tweeter. The speaker’s dimensions are 11.5” high by 9” wide by 12.25” deep. The enclosure has a front to back tapered shape and is composed of a special gray finished laminate material. The speaker grill is made of black perforated metal. The back of the speaker is an aluminum extrusion which acts as a heatsink for the power amplifiers output stage transistors. The structure is very rigid, non-resonant, and visually attractive. Internally, the SCM10A-2 features the ATC proprietary twin channel power amplifier with the Grounded Source output stage and the electronic crossover. The crossover is a fourth-order Linkwitz-Riley which provides a crossover frequency of 2.8 kHz and time (phase) alignment. Frequencies above the crossover frequency are sent to the 50 watt class A power amplifier that drives the tweeter and frequencies below are sent to the 200 watt class AB amplifier which drives the mid/woofer. The mid/woofer is awesome. I have never seen a 5” driver with such a massive motor structure. This accounts for the low distortion high output of the SCM10A-2. Connections to the speaker are at the back as one would expect. There is a female XLR for the line level input signal. The signal can be balanced or unbalanced. The input impedance is 10K ohms which is an easy load for solid-state preamplifiers but might prove to be less than optimum for some vacuum tube preamplifiers. The AC power input is via an IEC connector which sits next to the power switch.

The CA2 Preamplifier
The CA2 preamplifier is an attractive unit with a silver-gray chassis with a black anodized inlaid faceplate. The CA2 can be configured to accommodate five line level inputs or four line level inputs and one phono input. A phono card is optional. Looking at the unit from the front and going from left to right, you will see the volume control, input selector switch, and push button switches for the tape monitor, mute, and standby functions. Looking at the unit from the rear there are RCA jacks for the inputs and tape out. The line out is via a pair of male XLR connectors. The line outputs are not balanced even though XLRs are used. The headphone output is a standard quarter inch phone jack. Power into the unit is an IEC connector with the power switch above the connector. Looking inside the CA2 reveals two solid-state class-A amplifier circuits comprised of discrete components. Each amplifier has its own power supply. The amplifiers are designed to drive cables up to 50 meters in length with virtually no sonic degradation. The CA2 has an input impedance of 20k ohms which is no problem for the output from solid state gear. However the potential of gear with vacuum tube outputs might not be fully realized. The gain of the CA2 is about 16.5dB which translates to an amplification factor of about 6.67. This is more than adequate for most line level signals, particularly CD players. The level from lower output devices like phono stages and tuners might require that the volume control be turned past 12 o’clock to provide a satisfactory listening level. This is really no problem in practice.

The Setup
My listening room is about 22’ long by 12’ wide by 7.5’ high and is located in the basement of my home. My carpeted concrete floor is a big plus for clean bass and minimal high frequency reflection. The speakers were positioned along the short wall to fire down the length of the room. The wall and corners behind the speakers have been treated to be acoustically dead. This is not a true live-end dead-end (LEDE) approach but it works for this particular room. For this review the SCM10A-2s were placed on 2’ high rigid stands and positioned 6’ away from the back wall and about 2’ from the side walls with 7’ between speaker centers. The listening position is 10’ from the fronts of the speakers. Some rooms may require that the speakers be placed closer to the back wall to enhance the bass output.

During the review period the SCM10A-2s were driven with the CA2 and my reference solid-state preamplifiers with excellent results. The interconnect used between the preamplifiers and the SCM10A-2s were the Chord Chameleon 2 and my own custom designs. These interconnects gave excellent results with only minor differences between them. However, for this review I will focus on the sound reproduction capabilities of the ATC system (CA2 and SCM10A-2) with the Chord interconnects that Chris Barry supplied and recommended.

The Sound
Now we get to the heart of the matter. What is this thing called love? Well for me, in an audio sense, it’s this ATC system. You might be saying to yourself how can anyone get worked up over a small two-way with a 5” mid/woofer. Well my friends, prior to this fortuitous experience I would have been saying the same thing. But the more I listened, the more I loved what the ATC system was doing and not doing. LP after LP, CD after CD, the music just kept flowing. The ATC system is honest and faithful to the recording. It is as musically engaging as the source material permits. Bad recordings sound bad and great recordings sound great.

Many small speakers tend to sound small. Also, they tend to compress dynamic range particularly at high listening levels. You won’t have that problem with the SCM10A-2s. They are designed to put out a sound pressure level of 105dB at 1 meter continuously. The can be played loud with low distortion. The soundstage width, depth and height are basically determined by the recording.

The bass performance is exceptional in terms of quality. It is tight, clean, and articulate. The first disc I played was Super Bass 2 [Telarc CD-83483]. This is a recording of three master bassists, the late great Ray Brown, John Clayton, and Christian McBride. You can clearly hear the interplay of the three bassists along with their individual technique and bass tone. One of the best recordings of acoustic bass is Brian Bromberg’s Wood [A440 Music Group]. This CD was beautifully reproduced as well. In the event you plan to play music or soundtracks with deep high amplitude bass and want to feel the room shake, I would suggest adding a very high quality subwoofer to fill out the bottom and a half octaves. As good as the 5’ mid/woofer is, it simply does not defy the laws of physics. The bass output of the SCM10A-2s should be sufficient for most small to medium size rooms.

The midrange is as detailed and transparent as the best dynamic speakers. You won’t quite get the level of transparency and detail that electrostatic speakers can give but the response of the midrange is still very smooth. No particular frequency or band of frequencies is emphasized. Musical instruments with acoustic output that falls within this range are faithfully reproduced. Vocals, whether male or female, are also faithfully reproduced. Rachelle Ferrell, who I consider to be one of the most gifted musicians of our time, has incredible vocal technique and highly intelligent vocal arrangements. Her CD First Instrument [Blue Note CDP 7243 8 27820 2 5] showcases her talents as songwriter, arranger and vocalist. The ATC system allowed the emotion and dynamics of her voice to come through unimpeded.

The 1” soft dome tweeter reproduces high frequency information in an open, clear, and detailed manner. There is none of the etching, sibilant exaggeration, or high frequency ringing that some tweeters produce. Well recorded cymbals sound like they should, with a natural decay and shimmer. The upper ranges of violin and piano are beautifully reproduced.

Conclusion
The SCM10A-2 active speaker and the CA2 preamplifier provide the basis for an excellent music reproduction system that will bring big smiles to music lovers. This system is not biased to one particular type of music. You can equally enjoy classical, jazz, blues, and rock or anything else you desire. If you are looking for a high quality, high performance system for use in a small to medium size room, this ATC system might just be the ticket. Highly recommended.

H. Courtenay Osborne

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Specifications:
CA2
Main Output Level Amplitude: 7.5V into 600 ohms
THD: >110db
Crosstalk: 98db @ 10kHz
Frequency Response: DC - >200kHz
Output Impedance: 10 ohms
Tape Output: Direct
Input Impedance: 20k ohms
Input Sensitivity: 150mV for IV out at full gain
Connections: All inputs RCA style (phono) connectors. Main Outputs XLR unbalanced. Tape output RCA style (phono). Headphone 'Jack'
Power Supply: Selectable between 100V-230V
Power Consumption: 35VA max.
Dimensions(mm): 320x80x280 (HxWxD)
Weight: 6.8kg

Price: $2142.00

SCM10A-2
Drivers: Tweeter – 25mm (1”), Mid/Bass – 125mm (5”)
Cut-off Frequencies (-6dB free standing): 45Hz & 22kHz
Amplitude Linearity ±2db: 70Hz - 17kHz
Matched Response: ±0.5dB
Dispersion: Horizontal - ±80° Coherent, Vertical - ±10° Coherent
Max. continuous SPL (@ 1 meter): 105dB
Crossover Frequency: 2.8kHz via active crossover with time (phase) alignment
Input Connector: Male XLR
Input Sensitivity: 1V
Input Impedance: >10k ohms balanced XLR
Amplifier Output: HF – 50 watts rms, Mid/LF 200 watts rms
Overload Protection: Active Momentary Gain Reduction (both amplifiers)
Power Requirements: Voltage - 110, 115, 230 (factory set), Frequency – 50/60Hz, Power - Nominal 50 watts, driven 250 watts
Cabinet Dimensions (HxWxD): 290 x 230 x 310mm
Overall Weight: 15.5kg (34lb)
Stands/Brackets: Optional matching floor stands and wall brackets are available at extra cost

Price: $3900.00


Address
ATC (U.K.)
Gypsy Lane
Aston Down
Stroud
Gloucestershire
GL6 8HR.
Phone: 01285 760561
Fax: 01285 760683
Email: info@atc.gb.net

Flat Earth Audio (U.S. Distributor)

Distributors of ATC, MANA & SME
P.O. Box 110
Seymour, CT 06483
203-888-3759
203-888-3769 fax
www.flatearthaudio.com
fea@flatearthaudio.com