ATC C4 Sub Mk2 Subwoofer

£3,990.00£6,140.00 inc. VAT

Trade-in available.

Released in November 2023, the superb C4 Sub Mk2 by ATC is a high-performance active subwoofer, designed to deliver the exceptional levels of performance demanded by audiophiles, film lovers and music lovers worldwide.

Integral partnering with ATCs range of loudspeakers, the performance and features of C4 Sub Mk2 make it ideally suited to stereo, AV and home cinema applications.

Available in thirteen (13) finish options. Grille included.



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C4 Sub Mk2

The C4 Sub Mk2 by ATC delivers an extended low-frequency response without employing electronic equalisation, quite unlike many subwoofers available today.

Instead, the more elegant combination of exceptional transducer engineering and a marginally larger cabinet volume is used. The simplicity of this approach reduces phase shift and group delay, aiding the integration of the sub with the partnering monitor loudspeakers.

Ultimately, it delivers a more balanced and coherent experience for the listener, extending the low-frequency response without masking details or changing the tonal character in the upper bass / lower mid-range.

Drawing on 34 years of experience in amplifier design and development, ATC’s electronic engineering team have delivered an all-new amplifier for the new subwoofer. The 300W class AB design is hand-built by A TC at their UK facility and precisely optimised to the requirements of the drive unit, resulting in fast, dynamic bass with minimal colouration.

Two balanced inputs provide connectivity suited to both stereo and AV/home cinema systems plus two balanced outputs provide connections to partnering loudspeakers or to ‘daisy-chain’ multiple subs. Low-pass filters are analogue, 4th order Linkwitz-Riley and filter frequency options ensure optimal integration with a wide range of studio monitors.

An industry-standard 80 Hz low-pass plus an off option (for use with external processing) are also provided. A polarity switch plus a continuously variable 180° phase adjustment allows further optimisation of the subwoofer crossover, and a stepped attenuator with a 21 dB range provides precise level matching.


  • High performance sealed box design using 12-inch / 314 mm ATC proprietary sub driver.
  • Ideal partner to SCM19, SCM20, SCM40, SCM50, SCM100 loudspeakers.
  • Suitable for use in stereo / AV / home cinema applications.
  • On-board 300 W convention cooled discrete MOSFE T class A/B amp.
  • 2 x balanced XLR inputs.
  • 2 x balanced XLR outputs (unfiltered / processed).
  • User adjustable gain, low pass frequency, polarity and phase settings.


  • Amplifier: Grounded Source MOSFET based Class A-B, convection-cooled.
  • Output Power: 300 W into 8 Ω
  • THD+N: <0.003 % / -90 dB, at 100 Hz, 300 W into 8 Ω over 90 kHz bandwidth
  • Balanced Inputs: 2 x Rear Panel Mounted Female XLR, pin 2 hot
  • Input CMRR: 90 dB at 20 0Hz
  • Input Impedance: 20 kΩ (differential)
  • Balanced Outputs: 2 x Rear Panel Mounted Male XLR, pin 2 hot
  • Output Impedance: 100 Ω (differential)
  • Frequency Response: <2 Hz (-3 dB) – 320 Hz (-6 dB, set by panel-controlled LP filter)
  • Low Pass Filters: 4th Order Linkwitz Riley
  • Gain Control: 0 / +6 / +10 dB
  • Level Control: 0 dB – 11 dB in 1 dB steps.
  • Polarity Control: In-phase / Out-of-phase ref. Input
  • Limiter: A TC Active FE T Momentary Gain Reduction.
  • Sensitivity: 1.55 V rms for full power
  • Mains Input: 220-230 V or 115 V, factory set.
  • Power Consumption: Idle 8 W / 14 VA. 1/8th Power 170 W / 230 VA. Full Power 500 W / 600 VA.
  • Bass Drive Unit: 1 x SS75-314SC 8Ω
  • Low Frequency Cut-off: 2 2Hz (-6 dB, half space, low pass filter set at 80Hz).
  • Low Pass Filters: 50 / 65 / 80 / 320 Hz. (-6 dB, 4th order Linkwitz Riley).
  • Max SPL: 110 dB continuous, 116 dB peak.
  • Sensitivity: +4 dBu ref. 88 dBC.
  • Dimensions: (H x W x D): 568 x 465 x 519 mm
  • + Heatsink: Additional 40 mm depth.
  • + Optional Spikes: Additional 22 height.
  • Net Weight: 42 kg
  • Shipping Weight: 64 kg

Full ATC Range Available

Unilet Sound & Vision are official retail partners for ATC Loudspeakers, providing sales, advice and assistance on their entire range of high-quality audio products. Please do get in touch if you would like a demonstration or wish to purchase.

More Information

Additional information

Weight 42.0 kg
Dimensions 56.8 × 46.5 × 51.9 cm

Black Ash, Burr Magnolia, Burr Poplar, Cherry, European Walnut, Oak, Piano Black, Piano White, Pippy Oak, Rosewood, Satin Black, Satin White, Walnut

Purchase Options

Home Delivery, Click & Collect, Trade-In Available



Formed in 1974 by Billy Woodman to manufacture custom drive units for the professional sound industry, ATC Loudspeakers quickly became noticed with their 12-inch PA75-314 driver, a design capable of handling more power and producing less distortion at a higher SPL than any other unit then on the market.

Today, through an outstanding commitment to multi-channel mastering and direct involvement with leading players in the professional audio industry (including Sony Music and Telarc), ATC products are installed at some of the world’s most prestigious multi-channel studios and auditoria. Wherever the best is required, you will find ATC.

ATC Acoustic Engineers | Unilet Sound & Vision


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