ATC SCM20A SL

The ATC SCM20A SL Classic is a high-performance 2-way active stand-mount loudspeaker designed for critical listening in small to medium-sized rooms. In addition, it delivers studio-grade accuracy in a compact format where performance cannot be compromised.

The SCM20A SL Classic replaces a passive crossover system with an integrated active amplifier module. As a result, it achieves higher precision, better driver control, and improved dynamic range compared to passive designs.

Sealed cabinet for precise timing

The SCM20A SL Classic uses a sealed enclosure design. Therefore, it delivers tight timing and controlled low-frequency performance below the cutoff point. In addition, this design reduces resonance and improves overall clarity and transient response.

ATC 150 mm Super Linear mid/bass driver

ATC equips the speaker with a 150 mm Super Linear mid/bass driver. As a result, it produces accurate midrange reproduction and controlled bass response. At the same time, it maintains low distortion across a wide dynamic range.

25 mm S-Spec soft dome tweeter

The SCM20A SL Classic uses a 25 mm S-Spec soft dome tweeter with dual suspension. Therefore, it delivers detailed and extended high frequencies. In addition, it integrates smoothly with the mid/bass driver for a coherent overall sound.

On-board active amplifier system

The loudspeaker includes a 250 W on-board “Amp Pack” module. Therefore, each driver is powered directly by dedicated Class A/B amplifiers. In addition, this direct drive approach improves control, dynamics, and efficiency.

Active crossover and signal path

The SCM20A SL Classic uses a balanced input stage feeding a 2nd order active crossover. As a result, it provides precise level matching and timing between drivers. Furthermore, the active design reduces distortion compared to passive crossover networks.

User-adjustable tuning controls

The amplifier module includes adjustable input sensitivity and bass shelf controls. Therefore, users can fine-tune the speaker to match room acoustics and system preferences. In addition, this improves flexibility in different listening environments.

Rigid cabinet construction

ATC builds the cabinet to be heavy and inert with extensive bracing and damping. As a result, it minimizes unwanted vibration and cabinet coloration. In addition, bitumastic damping panels further improve structural stability.

Main Features

High-performance 2-way active stand-mount loudspeaker
150 mm ATC Super Linear mid/bass driver
25 mm S-Spec dual-suspension soft dome tweeter
Integrated 250 W on-board Class A/B amplifier module
2nd order active crossover (balanced input)
Direct drive amplification per driver
User-adjustable input sensitivity and bass shelf
Sealed cabinet design for precise timing
Heavy braced and damped enclosure construction
Hand-built in England
6-year warranty

Specifications

Acoustic Specifications

Mid/Bass Driver	1 × 150 mm (6″) SB75-150SL, 8 Ω
High Frequency Driver	1 × 25 mm (1″) SH25-76S, 6 Ω
Low Frequency Cut-off	55 Hz (−6 dB, anechoic)
High Frequency Cut-off	25 kHz (−6 dB)
Matched Response	±0.5 dB
Crossover Point	2.2 kHz
Maximum SPL	108 dB continuous / 114 dB peak (per pair, IEC weighted pink noise @ 1 m)
System Sensitivity	85 dBC SPL @ 1 m (pink noise, −18 dBu, 1 V input, 0 dB bass boost)

Electronic Specifications

Balanced Input	1 × XLR female (pin 2 hot)
Input Impedance	20 kΩ (differential)
Input CMRR	>60 dB @ 10 kHz
Input Sensitivity	2.2 dBu / 1 Vrms for full power
Sensitivity Adjustment	−6 dB switchable + −6 dB variable (up to 14.2 dBu / 4 Vrms range)
Bass Shelf EQ	−2 dB to +3 dB (1 dB steps)
Crossover Filters	2nd Order Linkwitz-Riley
Amplifier Type	Grounded Source MOSFET Class A/B (convection cooled)
Amplifier Power Output	200 W (bass) + 50 W (HF), 8 Ω
THD+N	<0.0017% / −95 dB (1 kHz, 1 dB below rated power, 90 kHz bandwidth)
Frequency Response	<2 Hz to >200 kHz (−3 dB)
Limiter	ATC Active FET Momentary Gain Reduction
Protection	DC offset & over-temperature (LED indication)
Mains Input	115 V / 230 V (factory set)
Power Consumption	Idle: 26 W 1/8 power: 116 W Full power: 312 W
Heat Output	89–382 BTU/hr (idle to full power)

Physical Specifications

Dimensions (H × W × D)	450 × 250 × 411 mm 17 11/16″ × 9 13/16″ × 16 3/16″
Net Weight	24.3 kg / 53.6 lbs