SCM20ASL LE and C4 Sub Mk2 LE 2024


The SCM20ASL Limited Edition is a 2-way active loudspeaker released to mark the beginning of ATC’s 50th Anniversary year. This exclusive new model, limited to just 150 pairs, packs ATC’s finest transducer engineering and active loudspeaker technology into a compact sealed cabinet, finished to exceptional standards in a stunning high-gloss blue lacquer. Complementing the cabinet, the front baffle is hand-upholstered in dark blue full-grain Napa leather.

Key Features:

  • Compact sealed cabinet finished in high-gloss blue with leather upholstered baffle
  • On-board ATC active 250W ‘Amp Pack’ module
  • 2nd order Linkwitz-Riley active crossovers
  • 2 x class A/B MOSFET amplifiers, 200W bass/mid & 50W high frequency
  • User adjustable input sensitivity & bass shelf controls
  • Hand-built in England

C4 Sub Mk2 LE

The C4 Sub Mk2 LE, limited to 20 units, is a high-performance 12″/300mm active subwoofer, designed to deliver the exceptional levels of performance demanded by audiophiles and film & music lovers and integral to partnering with ATCs range of loudspeakers. The subwoofer performance and features make it ideally suited to stereo, AV and home cinema applications.

Key Features:

  • High performance sealed box design using 12”/314mm ATC proprietary sub driver
  • Suitable for use in stereo, AV and home cinema applications
  • On-board 300W convention cooled discrete MOSFET class A/B amp
  • 2 x balanced XLR inputs
  • 2 x balanced XLR outputs (un-filtered/processed)
  • User adjustable gain, low pass frequency, polarity and phase settings
  • 6 Year warranty.



Acoustic Specifications

Bass/mid driver: 1 x 150mm/6”, SB75-150SL 8Ω
High Frequency Driver: 1 x 25mm/1”, SH25-76S 6Ω
Low Frequency Cut-off: 55Hz (-6dB, anechoic)
High Frequency Cut-off: 25kHz (-6dB)
Crossover Point: 2.2kHz
MaxSPL: 108dB continuous, 114dB peak (per pair, IEC Weighted Pink Noise, 1m, anechoic)
Sensitivity: +4dBu rev 95dBC (Bass Boost 0dB, Input Sensitivity 1V, Pink noise)

Electronic Specifications

Balanced Input: 1 x Rear Panel Mounted Female XLR, pin 2 hot
Input Impedance: 20kΩ (differential)
Input CMRR: >60dB (10kHz)
Input Sensitivity: 2.2dBu/1Vrms for full power
Input Sensitivity Control: -6dB switchable, -6dB variable. Total adjustment 2.2dBu/1Vrms to14.2dBu/4Vrms
Bass Shelf: -2dB to +3dB, switchable in 1dB steps
Crossover Filters: 2nd Order Linkwitz Riley
Amplifier type: Grounded Source MOSFET, class A/B, convection cooled
Output Power: Bass 200W (8Ω), H.F. 50W (8Ω)
THD+N: <0.0017%/-95dB (1kHz, 1dB below rated power, 90kHz BW)
Frequency Response: <2Hz to >200kHz (-3dB)
Limiter: ATC Active FET Momentary Gain Reduction
Electronic amp protection: Amplifier d.c. offset and over-temperature (both indicated by rear panel LED)
Mains Input: 220-230V or 115V, factory set. Please observe rear panel markings and labels!
Power Consumption: Idle 26W/41VA, 1/8th Power 116W/161VA, Full Power 312W/398VA
Heat Output: Idle 89BTU/hr, 1/8th Power 311BTU/hr, Full Power 382BTU/hr

Physical Specifications

Net Weight: 27kgs/59.5lbs
Dimensions: (H x W x D) 450x250x361mm / 17 11/16 x 9 13/16 x 14 3/16 inches
Amp pack protrudes a further 64mm / 2 1/2  inches from rear

Shipping Weights and Dimensions
Gross Weight: 31.3kg / 68.9lbs
Carton Dimensions (LxWxH): 56 x 38 x 60cm / 22 x 15 x 23 ½ inches
A carton contains a single speaker

C4 Sub Mk2 LE

Acoustic Specifications
Drive Unit – 12″ SS75-314SC 8Ω
Low Frequency Cut-off: 22Hz (-6dB, half space, low pass filter set at 80Hz).
Low Pass Filters: 50Hz, 65Hz, 80Hz, 320Hz. (-6dB, 4th order Linkwitz Riley).
MaxSPL: 110dB continuous, 116dB peak (IEC Weighted Pink Noise, 1m, half space, low pass filter @ 80Hz).
Sensitivity: +4dBu ref. 88dBC (single channel driven, Gain +6dB, Level 0dB, pink noise, low pass filter @ 80Hz).

Electronic Specifications
Amplifier type: Grounded Source MOSFET based Class A-B, convection cooled
Output Power: 300W into 8Ω
THD+N: <0.003%/-90dB, at 100Hz, 300W into 8Ω over 90kHz bandwidth
Balanced Inputs: 2 x Rear Panel Mounted Female XLR, pin 2 hot
Input CMRR: 90dB at 200Hz
Input Impedance: 20kΩ (differential)
Balanced Outputs: 2 x Rear Panel Mounted Male XLR, pin 2 hot
Output Impedance: 100Ω (differential)
Frequency Response: <2Hz (-3dB) – 320Hz (-6dB, set by panel-controlled LP filter)
Low Pass Filters: 4th Order Linkwitz Riley
Gain Control: 0, +6dB, +10dB
Level Control: 0dB -11dB in 1dB steps. Total range 21dB with use of Gain switch
Phase Control: 0-180° ref. Input
Polarity Control: In-phase/Out-of-phase ref. Input
Limiter: ATC Active FET Momentary Gain Reduction.
Sensitivity: 1.55Vrms for full power (single channel driven, Gain 0dB, Level 0dB)
Mains Input: 220-230V or 115V – Factory set. Please observe panel markings and labels!
Power Consumption: Idle 8W/14VA. 1/8th Power 170W/230VA. Full Power 500W/600VA.
Additional: Mute via ¼”/ 6.35mm Jack socket, controlled via latching footswitch*.
*Footswitch supplied separately, latching type, ¼”/6.35mm jack connection.

Physical Specifications
Dimensions: (H x W x D): 568 x 465 x 519mm / 22 3/8 x 18 5/16 x 20 7/16 inches
Heatsink protrudes a further 40mm / 1 9/16 inches from rear and optional spikes add an additional 22mm/ 7/8 inches to height.

Net Weight: 42kg / 92.6lbs.


In this series