Audio T Verdict
The ATC SCM40A combines the clarity and tonal accuracy of the passive SCM40 with amplification and active crossover filters designed specifically for its three drive units.
A dedicated 150W amplifier controls the bass driver, with separate 60W and 32W channels powering ATC’s renowned soft-dome midrange and high-frequency driver. This direct relationship between amplifier, crossover and driver gives the SCM40A impressive control, consistency and dynamic freedom.
The sealed cabinet produces bass that is tight, accurate and easier to follow rhythmically than many reflex-loaded alternatives. The dedicated 75mm midrange remains the defining feature, reproducing voices and instruments with exceptional openness and natural detail.
A suitable pre-amplifier or source with a properly controlled variable output is essential. Each speaker also requires its own mains supply and line-level XLR connection.
ATC SCM40A Three-Way Active Floorstanding Speakers
The ATC SCM40A is a three-way active floorstanding loudspeaker system supplied as a stereo pair.
Each enclosure combines ATC’s 164mm bass driver, 75mm soft-dome midrange and 25mm dual-suspension tweeter with three dedicated Class A/B amplifier channels and an active electronic crossover.
This integrated design removes the need for a separate stereo power amplifier while allowing ATC to optimise the crossover, amplification and drive units as one complete system.
How Active Loudspeakers Work
A conventional passive speaker receives a full-range amplified signal and divides it between the drivers using a passive crossover inside the cabinet.
The SCM40A divides the incoming line-level signal before amplification. Bass, midrange and high frequencies are then passed to separate amplifiers connected directly to their corresponding drive units.
This avoids placing a high-power passive crossover between the amplifier and driver, while giving ATC precise control over crossover filtering, phase behaviour, amplifier output and overload protection.
A Pre-Amplifier or Controlled Variable Output Is Required
The SCM40A does not provide source selection or a conventional listening-volume control.
It must be connected to a suitable pre-amplifier, streamer or DAC with a safe and properly controlled variable analogue output. A fixed-level source must not be connected directly.
242W of Tri-Amplification per Speaker
Each SCM40A contains three grounded-source Class A/B amplifier channels, providing 242W of combined output.
- Bass amplifier: 150W
- Midrange amplifier: 60W
- High-frequency amplifier: 32W
The power is distributed according to the requirements of each drive unit rather than being shared through a passive crossover.
This dedicated arrangement helps the speaker maintain control during demanding bass passages while preserving midrange clarity and fine high-frequency detail.
Dedicated 75mm Soft-Dome Midrange
ATC’s 75mm soft-dome midrange is central to the SCM40A’s performance.
Much of the human voice and the defining tonal character of musical instruments falls within the range reproduced by this dedicated driver.
Relieving the bass driver of midrange duties helps reduce distortion and allows voices, strings, guitars, brass and percussion to remain natural and clearly separated when recordings become complex.
Its broad, controlled dispersion also contributes to stable stereo imaging across a useful listening area.
ATC 164mm Bass Driver
Low frequencies are handled by ATC’s 164mm short-coil bass driver, powered directly by its dedicated 150W amplifier.
Its substantial motor assembly and carefully controlled voice-coil geometry are designed to provide low distortion and accurate movement throughout the driver’s operating range.
Combined with the sealed cabinet, the bass driver prioritises pitch definition, timing and control rather than using a reflex port to add artificial upper-bass weight.
ATC Dual-Suspension Tweeter
High frequencies are reproduced by ATC’s 25mm dual-suspension soft-dome tweeter with a precision alloy waveguide.
Supporting the dome at two points helps control unwanted movement and allows the tweeter to operate without ferrofluid within the magnetic gap.
The precision waveguide controls dispersion and supports a smooth transition from the soft-dome midrange.
ATC matches the response of the stereo pair to within approximately 0.5dB, helping produce consistent tonal balance and precise imaging.
Active Crossover and Phase Compensation
The SCM40A uses active crossover frequencies of 380Hz and 3.5kHz.
Fourth-order critically damped filters divide the incoming signal before amplification, with phase compensation used to support coherent integration between the three drive units.
The crossover and amplifier electronics are designed together, removing the uncertainty involved in matching an external amplifier to a passive crossover network.
Integrated Protection
Active FET momentary gain reduction protects the system during excessive signal peaks without relying solely on conventional fuse protection.
The SCM40A also includes DC fault protection and a thermal trip, with fault indication provided by an LED mounted on the rear panel.
Protection circuitry should not be treated as a substitute for responsible use, but it provides additional security during demanding playback.
Balanced XLR Inputs
Each speaker provides a female XLR line-level input with a sensitivity of 1V.
A complete stereo system therefore requires two analogue signal cables, with one cable running from the controlling pre-amplifier or source to each speaker.
Balanced connections are particularly useful when the speakers are positioned several metres away from the source equipment, helping reduce susceptibility to electrical interference.
Matching ATC Pre-Amplifiers
The
ATC SCA2 reference pre-amplifier
is the natural high-level partner, providing balanced source connections and balanced XLR outputs suitable for longer cable runs.
The more compact
ATC CA2 Mk2 pre-amplifier
provides analogue system control, record playback and headphone listening.
A compatible streamer or DAC with a high-quality variable output may also connect directly, provided its volume behaviour and output compatibility are fully understood.
A Streamlined Active System
Because the power amplification is built into the speakers, the SCM40A can form a high-performance system with relatively few separate components.
A suitable streaming pre-amplifier can provide music streaming, digital conversion, source selection and volume control in a single component, with balanced analogue cables running directly to the speakers.
Read our
guide to streamlined active Hi-Fi systems
for more information about this type of setup.
Sealed Floorstanding Cabinet
The SCM40A uses a sealed enclosure rather than a reflex port.
This avoids port noise and gives the low-frequency response a gradual roll-off, prioritising timing, pitch definition and control.
The curved cabinet is laminated, internally braced and damped to reduce unwanted vibration and internal resonance.
Although the sealed design offers useful positioning flexibility, nearby walls and corners will still increase bass output and should be considered during installation.
48Hz to 22kHz Frequency Response
ATC specifies a frequency response extending from 48Hz to 22kHz at the stated minus 6dB points.
The SCM40A is designed to reproduce low frequencies accurately rather than adding an exaggerated upper-bass lift to make every recording sound artificially large.
Where deeper extension is required, a carefully positioned and adjusted active subwoofer can complement the speakers.
The
ATC C1 Sub Mk2
provides a natural option for music and home cinema systems.
112dB Maximum Output
ATC specifies a maximum sound pressure level of 112dB.
This provides useful dynamic headroom for orchestral music, rock, electronic recordings and other material with significant contrasts between quiet and loud passages.
The SCM40A’s ability to play loudly is combined with ATC’s emphasis on clarity, tonal accuracy and low distortion.
Room Positioning
Begin with the speakers positioned symmetrically and given moderate clearance from the rear and side walls.
Adjust the distance between the speakers, their wall clearance and toe-in gradually while listening to familiar recordings.
The preferred position should produce a stable central image, controlled bass and an even tonal balance without allowing nearby boundaries to dominate the presentation.
Integrated Foot Plinth and Spikes
The SCM40A includes an integrated foot plinth and is supplied with four M8 floor spikes per cabinet.
The spikes add approximately 25mm to the cabinet height. Both speakers should be levelled carefully so they remain stable and do not rock during use.
Suitable spike shoes or floor protectors should be used on wood, laminate, tile and other vulnerable surfaces.
Allow for the Full Installed Dimensions
Each speaker measures 980 x 370 x 344mm and weighs 36kg. The spikes increase the installed height to approximately 1005mm, while the grille increases the overall depth to approximately 378mm.
Additional space is required behind each cabinet for its XLR connection, mains lead and ventilation.
SCM19A or SCM40A?
ATC SCM19A
- Two-way active floorstanding design
- 150mm Super Linear mid and bass driver
- 182W bi-amplification per speaker
- More compact cabinet
- Suited to smaller and medium-sized rooms
View the ATC SCM19A
ATC SCM40A
- Three-way active floorstanding design
- Dedicated 75mm soft-dome midrange
- 242W tri-amplification per speaker
- Greater bass and dynamic scale
- Suited to medium-sized and larger rooms
Active SCM40A or Passive SCM40?
SCM40A Active
- Three amplifiers built into each speaker
- Active electronic crossover
- No separate stereo power amplifier required
- Female XLR signal input
- Each speaker requires mains power
- Amplification is selected and matched by ATC
SCM40 Passive
- Requires a separate stereo amplifier
- Allows independent amplifier choice
- Uses a passive three-way crossover
- Conventional speaker-cable connection
- No mains connection at the speakers
- Offers greater future amplifier flexibility
View the passive ATC SCM40
Finish Options
Cherry
A warm natural veneer with individual variation in grain, colour and shade.
Black Ash
A dark natural veneer with visible grain and an understated appearance.
Satin Black
A uniform painted finish suited to contemporary systems and darker furniture.
Satin White
A brighter painted finish designed to complement lighter rooms and modern interiors.
System Matching
Well Suited To
- High-performance active stereo systems
- Medium-sized and larger listening rooms
- ATC SCA2 and CA2 pre-amplifiers
- Streaming pre-amplifiers with variable outputs
- Longer balanced interconnect runs
- Listeners prioritising clarity and accuracy
- Low-box-count reference music systems
Check Before Buying
- Each speaker weighs 36kg
- Each cabinet requires a mains connection
- A pre-amplifier or variable output is required
- Two line-level XLR cables are required
- The rear amplifier increases cabinet depth
- Room boundaries will affect bass balance
- Natural veneers vary in appearance
Setup Guidance
- Connect all equipment while switched off
- Begin with the controlling volume set low
- Install and level the floor spikes carefully
- Use floor protectors on vulnerable surfaces
- Keep signal cables separated from mains leads
- Begin with moderate wall clearance
- Adjust toe-in using familiar recordings
Browse our
stereo speakers
,
pre-amplifiers and Hi-Fi amplifiers
,
music streamers
,
digital-to-analogue converters
,
Hi-Fi subwoofers
and
analogue interconnects
, or explore the complete
ATC range at Audio T
.
Key Features
- Three-way active floorstanding loudspeaker system
- Supplied as a stereo pair
- ATC 25mm dual-suspension soft-dome tweeter
- Precision alloy high-frequency waveguide
- ATC 75mm soft-dome midrange driver
- ATC 164mm short-coil bass driver
- Grounded-source Class A/B tri-amplification
- 150W bass amplifier per speaker
- 60W midrange amplifier per speaker
- 32W high-frequency amplifier per speaker
- 242W total amplifier output per speaker
- Active fourth-order crossover filters
- Integrated phase compensation
- Active overload and fault protection
- Female XLR input on each speaker
- 48Hz to 22kHz frequency response
- 112dB maximum sound pressure level
- Matched response within approximately 0.5dB
- Sealed, curved and internally braced cabinet
- Integrated foot plinth and adjustable spikes
- Cherry, Black Ash, Satin Black and Satin White finishes
- Warranty extendable to six years following qualifying registration
Frequently Asked Questions
Are the ATC SCM40A speakers supplied as a pair?
Yes. The SCM40A is supplied as a stereo pair.
Do they require a separate power amplifier?
No. Each speaker contains dedicated bass, midrange and high-frequency amplifiers.
Do they require a pre-amplifier?
They require a suitable pre-amplifier or source component with a properly controlled variable analogue output.
What connections are required?
Each speaker requires its own XLR signal connection and mains connection.
How powerful are the internal amplifiers?
Each speaker provides 150W for bass, 60W for midrange and 32W for high frequencies, creating 242W of tri-amplification.
What is the difference between SCM40 and SCM40A?
The SCM40 is passive and requires an external amplifier. The SCM40A contains an active crossover and three dedicated amplifier channels within each speaker.
Can a subwoofer be added?
Yes. A suitably positioned and adjusted active subwoofer can extend the system’s lowest frequencies.
How large and heavy is each speaker?
Each cabinet measures 980 x 370 x 344mm and weighs 36kg. The spikes add approximately 25mm to the height and the grille adds around 34mm to the depth.
Why Buy From Audio T?
- ATC active-speaker demonstrations
- Pre-amplifier and variable-output source matching
- XLR interconnect and cable-length guidance
- Comparison with passive ATC loudspeakers
- Room-positioning and toe-in assistance
- Subwoofer and system-integration advice
- Floor-spike and surface-protection guidance
- Streaming, DAC and turntable system matching
- Ongoing setup and system-development support
Contact your local Audio T store
to discuss matching and installing the ATC SCM40A within your room and music system.