ATC SCM20 Bookshelf Loudspeaker Reviewed

Published On: February 13, 1990
Last Updated on: October 31, 2020
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ATC SCM20 Bookshelf Loudspeaker Reviewed

Although it is not a very large unit, ATC has endowed the SCM20 "with dynamic capabilities which are found only in massive or expensive systems." In fact, our reviewer noted he had "yet to find much material which taxes the SCM20. It also avoids "any fatigue-inducing 'edges'" while vocals

ATC SCM20 Bookshelf Loudspeaker Reviewed

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ATC-SCM20-Review.gifBribery, hypnosis, threats -- it doesn't matter what method you
employ. If your other half doesn't want big speakers in the
house, t'ain't nothing you can do but opt for a smaller system.
And it's tough if you have your heart set on a specific brand
with no small system in its line-up. For readers who have tasted
the delights of ATC's studio monitors, it's been a long wait, but
they've finally come up with a model which precludes the domestic
battles preceding the purchase of the SCM50s or SCM100.

Read more high end bookshelf speaker reviews from B&W, PSB, Paradigm, LS3/5a and many more.

The SCM20 has been on the drawing board for nearly four years,
though eagle-eyed and eared show visitors will have seen and
heard prototypes from various points in the model's evolution.
ATC wisely chose to demonstrate these prototypes over the past
two years, not to antagonize but to tantalize. Only by showing
that the company was serious about offering a small system could
it prevent space-shy, would-be ATC owners from shopping elsewhere
in despair. That's because these prototypes promised a manageable
box boasting all of the virtues which have made ATC the choice
for the BBC, Abbey Road Studios, Pink Floyd, Nimbus, Peter
Gabriel and a bunch of other major players.

The virtues present in the SCM20 include every one of the
company's signature techniques bar the option for active
versions; the box is simply too small to contain one of the
company's onboard amplifiers. That aside, the similarity to the
larger, dearer beasts is absolute, beginning with the same 25mm
viscous damped fabric dome tweeter sourced from Vifa in Denmark.
The tweeter features ferro-fluid cooling for high power handling
and therefore greater reliability. We as domestic users benefit
from the uncouth behavior of studio habituees because products
designed for the pro sector are expected to be abused. ATC, like
other monitor builders, is forced to over-engineer everything
they offer; the result is a tweeter which should withstand
whatever a hi-fi user can throw at it.

What's new to this model is the ATC-designed and manufactured
180mm bass unit, notable because the magnet is as large as the
driver itself. Dubbed the SB75-150 Sc (ATC makes its drivers
available to other manufacturers, hence a model number), the
woofer incorporates a polyester-weave diaphragm coated with an
ATC-developed damping material. The 75mm diameter voice coil is
made from copper ribbon wire around a Kapton former; length of
the coil is 8mm, with a gap length of 20mm, and maximum cone
excursion is a whopping 40mm before there's any risk of damage.

The magnet features a vented pole piece and a 20mm thick front
plate, the assembly glued and bolted with four 8mm cap screws.
This in turn is fixed to a low pressure die-cast aluminum
chassis with eight 5mm cap screws, looking as structurally sound
as one of those multi-part alloy wheels favored by the likes of
Ferrari. To give you some idea of the sheer confidence this
bullet-proof construction inspires, each woofer assembly weighs

The drivers cross over at 2kHz via a 10-element network made up
of massive individually-calibrated, hard-wired, hand-wound air
core inductors and hand-made 150V AC metalized polypropylene
capacitors. Compensation for level differences between drive
units is via T-Pad resistor networks to ensure that the load as
seen by the amplifier does not change. Despite being one of the
hungriest speakers this side of an Apogee -- a gluttonous 83dB
for one watt at one meter -- it presents an easy load, its
nominal 8 ohm impedance never dropping below 5.4 ohms. Bi-wiring
is not an option with this speaker, which reflects ATC's desire
to manufacture products which are complete in themselves, so as
best to ensure their performance. (This is also an irrefutable
argument in the defense of active systems employing amplifiers
designed specifically for the speaker.)

The enclosure, measuring a manageable 440x240x310mm (HWD), is a
cabinet-tapper's delight. Made from 18mm thick veneered MDF with
a 36mm thick baffle, it's lined internally with 6mm thick
bitumastic sound deadening pads. The review pair, in the optional
yew veneer instead of the standard walnut or black, was quite
simply the most beautifully finished speaker I have seen in
years. Kudos go, I believe, to Castle for the woodwork, which
takes a lot of the sting out of the #1320 per pair price tag. In
other words, the small ATCs, like the Sonus Fabers and Monitor
Audio Studio 10s, are among very few small high-priced systems
which reek of perceived value. And the cabinet-rappers will
rejoice, because the construction is dense enough to endow the
SCM20 with a weight of nearly 23kg apiece.

Completing the package is a thin black grille which fits snugly
around the raised baffle. Its frame is substantial, but the
design is open-edged to prevent diffraction problems. Listening
tests confirmed that the grille should be left in place.

ATC has a reputation for conservatism (small 'c') and have in the
past been at odds with the hi-fi community. Without suggesting
that the company is yet at a stage where it will be supplying,
say, free Calotherm 'magic cloths' with each speaker, ATC does
take seriously such details as speaker stand selection, choice of
cable and the quality of the terminals. On the SCM20, the company
uses a hefty gold binding post sourced from Michell; my only
complaint is that the hole for banana plugs was undersized even
for Michell's own bananas. Speaker cable comments are limited to
suggesting minimum thicknesses according to the lengths of the
cable runs and a simple 'single strand solid core cable is
unsuitable', with which I heartily concur. It's the speaker stand
requirements, though, which are slightly out of the ordinary.

Naturally, you'd expect a speaker weighing 50lb in old money
(¬don't¬ convert that to metric, Trevor) to need a rugged,
substantial stand. Fair enough. What I was not ready for was the
need to place the SCM20s on stands as tall as the 24in (ditto,
Trevor) Partington Dreadnoughts, thinking that a speaker
measuring 440mm tall would have been better suited with 25% less
lift. As it turns out, the added height compensates for very
limited vertical dispersion, which ATC acknowledges. The
instructions advise listeners to install the speaker so that the
bass driver rather than the tweeter is aligned with the
listener's ear. Although many small two-ways -- the LS3/5A, the
Infinity 2001, the Sonus Fabers -- can boast exceptional image
height, the SCM20s simply produce a field which corresponds
approximately to the height of the speaker baffle. By positioning
the SCM20 with the woofer at ear height, the listener won't feel
too cheated in this respect.

Stage width, on the other hand, borders on the sensational. The
SCM20 effectively opens the sound with enough of a spread to
counter what might have been a squashing effect due to limited
height dispersion and only average front-to-back depth. As a
result, the SCM20 is not the speaker I'd recommend to anyone who
places three-dimensionality above the more important sonic
attributes. The SCM20 still manages to sound like a large
speaker, partly because of the 'open plains' stage width and
partly because the speaker delivers dynamic and high levels
without any strain; it's just not the speaker I'd use to show off
Willy de Ville's 'Assassin Of Love' or the Human League's 'Don't
You Want Me'.

ATC isn't too bothered by this because their priorities are sonic
rather than spatial. I can't really argue, because -- in reductio
-- I too would rather enjoy perfect mono than awful stereo. So
what ATC focusses on are low distortion, controlled bass,
detailed treble and a resistance to compression due to vast
dynamic and/or level swings. And in these respects, the SCM20 is
a champion, especially given that the enclosure is probably
smaller than even the amplifiers which will be used to drive it.

Don't let the easy impedance fool you into mating the SCM20 with
any amp less than 'substantial'. I tried no less than six power
amplifiers and the absolute minimum with which I was completely
happy was the Aragon 4004, a 200W/channel amplifier costing some
#500 more than ths ATCs. Although I heard superb sounds issuing
from the ATCs when they were driven by the Croft 60W/channel OTL
power amplifier (at #999), some compression during crescendos
could be heard when the levels were boosted to just above
'normal', or 84dB at 2m in my parlance. And as for the #17,000
Carver Silver Sevens, well, it was glorious but at the same time
too ludicrous to contemplate.

Remember that the difficulty in driving the ATCs, aside from a
revealing nature which will show up any amplifier-related sonic
deficiencies, has nothing to do with vicious impedances; tube
amplifiers, therefore, need not be eliminated as possible power
sources. It's simply a matter of brute force, and ATC quite
accurately recommends a real 100W/channel if a pair of SCM20s are
to be welcomed in your home.

They're speakers which will creep up on you, one of those odd
occurrences where you don't really know how good a product is
until you take it away. While they're impressive by any small
monitor standards, the initial surprises -- De Mille-ian stage
width, better-than-you'd-expect bass, the ability to pump out the
SPLs -- are also available from like-sized competitors for the
same or less money. But not all at once.

As with any review of a small loudspeaker, the first area which
must be addressed is that of bass reproduction. Why? Because it's
usually where most of the sacrifices occur, at least until the
laws of physics are repealed. ATC states a -6dB point of 55Hz,
with the speaker's lowest response of +/-2dB being 80Hz. What
this translates to in practice is a speaker which is never less
than adequate for the majority of recordings bar those which are
heavy on synthesizers, church-type organs or big percussion. The
clever bit, though, is two-part.

The first is dealing with the roll-off in a graceful manner,
allowing the speaker to excuse itself from deep-bass duties in a
way which doesn't show up this particular inadequacy. Just as the
Wilson WATT stops dead and says, 'Hey, I ain't goin' no lower and
that's that', so does the SCM20 make a stance by simply reducing
its output in a consistent and non-jarring way. Either approach
is valid, but the latter manages to squeeze out a bit more than
the former.

Read more on Page 2


The second part of the quart-in-a-pint-pot tradition is to exploit other areas of bass-related performance so as to distract the listener from the missing bottom notes. The LS3/5A, for example, has for years fooled people with its carefully applied frequency bump in the 100-125Hz region. What ATC has done is endowed the SCM20 with dynamic capabilities which are found only
in massive or expensive systems. That exceptional cone travel of 40mm, the ferro-fluid cooling, the watch-like build tolerances and the bomb-proof enclosure combine to provide the dynamic capabilities which allow the SCM20 to play loud without compression and without blurring any low level information.

Read more high end bookshelf speaker reviews from B&W, PSB, Paradigm, LS3/5a and many more.

Whether or not dynamic contrasts are a substitute for sheer
weight can only be determined by either your personal tastes or
musical preferences. Even when comparing the SCM20s to much
larger systems such as the Apogee Diva (image height
notwithstanding), I find the small ATCs' shortcomings to border
on the insignificant. Unlike readers who indulge in a diet
consisting primarily of orchestral music or the kind of synthetic
funk which spans 20-20kHz (courtesy of Yamaha, Roland and
Synclavier), I have yet to find much material which taxes the
SCM20. Back to the Willy de Ville track, its Stygian bass notes
were marginally less powerful than when heard through the Stage
or Diva. The Depeche Mode colossus 'Personal Jesus' also exposes
this. On the other hand, the notes were so well-controlled that
what was lost in quantity was more than compensated for by

But people don't buy small speakers if bass is a priority. The
ATCs excel in the midband and treble, delivering clean, detailed,
undistorted sound at high levels, enough to appease the most
critical sound engineer while at the same time avoiding any
fatigue-inducing 'edges'. This means that either the professional
or the civilian can listen to the ATCs for hours on end without
inviting earache. Vocals, particulary those with lots of
character like Leon Redbone's or Willy de Ville's, are reproduced
in such a lifelike manner that the net result is an above-average
number of goose bumps.

The SCM20 is not perfect, and I'm not about to gloss over the
loss of image height or the lack of extreme bass. But in all
other areas it comes close to being the best small monitor I've
ever used. The only real competitors are the similarly-priced
Sonus Faber Electa or the dearer Amator, but they opt for greater
'musicality' rather than accuracy. In other words, the latter are
more forgiving. But on balance, both have an equal number of
strengths and weaknesses, so an arbitrary points system would peg
them at a draw. In which case you've gotta do what an
audiophile's gotta do: listen to them.

Competitors aside, ATC has delivered on its promise of an SCM50
or SCM100 for the real world. It's a wee masterpiece, and it
makes me more impatient to hear their next offering, an even
smaller system at half the price due in '92.

But maybe I shouldn't have told you that...

Read more high end bookshelf speaker reviews from B&W, PSB, Paradigm, LS3/5a and many more.

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