ATC SCM7 v.3 loudspeaker

In 1974, in England, Australian Reverse-Pommy pianist and recording engineer Billy Woodman founded the Acoustic Transducer Co. (ATC) as a maker of loudspeaker drive-units. That makes ATC a few years younger than Spendor (1969) and a few years older than Harbeth (1977). When I mentioned all that to a quick-witted audio buddy, he immediately came back with "Middle Child Syndrome!"

It does seem that ATC has gotten less attention in the US than its older and younger British siblings. In an effort to rectify that, ATC is updating their loudspeaker designs and changing their US distribution arrangements.

ATC developed the first soft-dome midrange driver, and pioneered self-contained active (ie, powered) speakers. The company remains independently owned, and their products—which include preamplifiers, power and integrated amplifiers, a CD player–DAC, and a new CD receiver with USB input—are made in England. Celebrity owners of ATC speakers include T Bone Burnett, Coldplay, Enya, Diana Krall, Lenny Kravitz, Ziggy Marley, Tom Petty, Pink Floyd, the late Lou Reed, the Rolling Stones, Paul Reed Smith, Sting, and Roger Waters. The last pair of loudspeakers Stereophile founder J. Gordon Holt purchased were ATCs.

ATC offers both Professional and Consumer lines of speakers, the latter in wood veneers and, usually, in both passive and active versions. The four models in their Consumer Entry Series, including the entry-level Entry SCM7, are passive only. All of ATC's Professional speakers are active, with some also available in passive form. With two exceptions, the pro models are offered in a finish of semigloss black paint.

In many instances, ATC constructs pretty much identical speaker designs for both markets. One such pair of twins is the SCM50, with ATC's 1" soft-dome tweeter, 3" dome midrange, and 9" woofer. The Consumer SCM50 is available (as active or passive) in a choice of Black Ash, Cherry, Maple, Oak, Pippy Oak, Rosewood, and Walnut, or (by special order) in a veneer of any legally available hardwood. The Professional SCM50 is available (as active or passive) in black paint, and has a blanked-off cutout on the front panel to enable relocation of the tweeter above the midrange driver if the cabinet is to be positioned horizontally rather than vertically. The passive pro model uses a Speakon connector for its amplifier input.

However, such design twinship is not always the case. The entry-level SCM16A Pro and SCM20ASL Pro active monitors (both about to be replaced, though old stock may still be available) have distinctive aluminum cabinets with curved sidewalls and radiused front panels and edges, built-in front-panel tilt-back, and no grilles. Those two aluminum cabinets are unique to the Pro line. There are also Pro models with double woofers that lack exact Consumer twins, in that the Pro versions are stand-mounted while the Consumer versions are towers.

One Consumer speaker appears to be in a class of its own. The EL150 is ATC's "statement" model, at $47,770/pair passive and $84,999/pair active, in the standard veneer of burr magnolia. Its very wide and shallow cabinet is reminiscent of Sonus Faber's Stradivari or Elipsa. (An ATC speaker's model number indicates its internal volume, in liters; eg, the SCM19 has a volume of 19 liters.)

Perhaps one reason ATC's profile in the US has always been lower than Harbeth's or Spendor's is because US audiophiles historically have resisted the idea of active speakers. Although powered speakers offer advantages in implementing crossover slopes and in amplifier efficiency, over the years, I've been told many times that US audiophiles absolutely insist on choosing their own power amplifiers and speaker cables.

I wonder whether that conventional wisdom might be crumbling. What makes me think that US audiophiles might be getting ready to seriously consider ambitious active speakers is the market success of such models as Audioengine's 5+ ($399/pair). I don't think that all of Audioengine's customers are using their 5+s on desktops with computers; I suspect that many use them as the main speakers of a stereo system. Time will tell.

I wrote about ATC's SCM11, a two-way stand-mounted speaker, in December 2009 and about the SCM40, a three-way tower with ATC's famous dome midrange, in April 2010. John Atkinson concluded his measurement report on the SCM11 with this: "The ATC SCM11 is a well-engineered little speaker. I am not surprised John Marks liked it as much as he did, though I would point out that its measured behavior suggests it will work better when listened to fairly close."


I'd been lent the SCM11 and SCM40 by ATC's then importer and distributor for its Consumer models, Flat Earth Audio, of Connecticut. In mid-2013, ATC decided to consolidate its US presence by reassigning the responsibility for consumer speakers to Transaudio Group, which had represented ATC's professional products in the US for many years. To emphasize its expansion into the consumer market, Transaudio has established a subsidiary, Lone Mountain Audio. At present, Lone Mountain Audio represents only ATC.

Because I was revisiting the broader subject of professional equipment that audiophiles should know about (such as the Lindell AMPX class-A power amplifier I wrote about last December), or at least consumer equipment with professional roots, I requested the loan of ATC's Consumer SCM19, the next size up from the SCM11. The SCM19 is also ATC's least-expensive loudspeaker whose woofer incorporates their Super Linear magnet technology. I was then told that ATC was updating all its models, starting with the smallest, the SCM7, and that the updated SCM19 would not be available for several months.

I agreed to review the SCM7 because I was curious what ATC's updated entry (this is v.3) in the evergreen British Shoebox Monitor sweepstakes would sound like—that despite Lone Mountain Audio's Brad Lunde hastening to point out that the SCM7 contains no more BBC LS3/5A DNA than any other British-made shoebox-sized two-way. ATC's design goals for the SCM7 are to offer a minimonitor with excellent dynamics and best-in-class bass. For the first time, the tweeter has been designed and built in-house by ATC.

The SCM7 v.3
The cabinet of the previous-generation SCM7 had square corners and flat sides—definitely a 1980s–90s look. Its drivers were mounted on a black-painted baffle board with radiused edges and grille-attachment grommets. This board covered most of the front panel, the rest of which was veneered.

ATC Loudspeaker Technology Ltd.
US distributor: Lone Mountain Audio
7340 Smoke Ranch Road, Suite A
Las Vegas, NV 89128
(702) 307-2727

Supperconductor's picture

Headline typo.

John Atkinson's picture

Thanks - JA

audiolab's picture

I know you are right in that low c on a piano is 27.5hz, I will not argue that low c on a bass guitar is 41hz (I do not know of such things), but who decided low c on an organ is 32hz. Any half decent sized organ in a cathedral or concert hall will have a 32ft stop that yields a low c of 16hz. Some people would point you to two organs in the world that have a 64ft stop that yields a low c of 8hz, some would even point out that technically one of those two could play a resultant tone of a 128ft stop resulting in a almost purely accademic low c 4hz. I am quite happy to settle with it at 16hz and what a wonderful note it is to !

John Atkinson's picture

audiolab wrote:
I will not argue that low c on a bass guitar is 41hz

The low E string (not C) on a bass guitar or double bass is tuned to 41.2Hz, but most of the energy lies an octave higher, at 82.4Hz. See fig.3 at

John Atkinson
Editor, Stereophile

jmsent's picture

In the absence of enclosure resonance as an explanation, that fairly substantial dip in the measurement between 600 and 1 kHz might be the result of a woofer "edge resonance". Surprising, given the pedigree of the company.

John Atkinson's picture

jmsent wrote:
that fairly substantial dip in the measurement between 600 and 1 kHz might be the result of a woofer "edge resonance".

I had wondered if that were the problem, but I thought that cone/surround termination problems occurred a little higher in frequency, between 1kHz and 3kHz.

John Atkinson

Editor, Stereophile

jmsent's picture

I would normally take place a bit higher up in frequency on a driver this size. But certain cone/surround combinations can push it down. But whatever the cause, that sharp dip is fairly severe, and I'm still surprised they'd let it go to market with this flaw.

RoryB's picture

Looking at the magnitude of the peak/dip couplet, which does look like a surround resonance (probably due to the relatively wide surround; a Klippel scanning laser vibrometer could reveal the true cause), it is visible in the graph but at +3/-3dB in magnitude, it is not terribly severe. At the lower frequency where it occurs, you are less likely to notice it. You might notice it more as a coloration if it occurred at 2-3 kHz, and more would need to be done to correct it. A thicker surround or a variable thickness surround could correct this problem, but it would reduce broadband sensitivity of the driver.

Bob Loblaw's picture

In the article the term active and powered to describe speakers with built-in amplification is used interchangably. They are not the same thing. An active speaker has an active crossover and 1 amplifier for each driver, such as with ATC's active speakers.

A powered speaker is a passive speaker with an amplifier built in. The Audioengine A5+ is a powered passive speaker.

Active speakers have several advantages over passive and powered passive speakers and it's a disservice to your readership not to acknowledge the difference when there are those out there who may not know better.

ryder's picture

I am well aware that small monitors cannot go too loud or too deep in the bass. Having said that, can this SCM7 v3 go loud without losing control at moderate to high volume levels? Can it go louder than say the Harbeth P3ESR?