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ATC launches NEW C4 SUB MK 2 Active Subwoofer


ATC Loudpeakers are launching the C4 Mk 2 active subwoofer system. Designed to unite the highest standards of driver and electronics engineering in a single system, the C4 Sub Mk 2 deploys the all-new proprietary 12-inch SS75-314SC sub-bass driver powered by a newly developed 300W class AB amplifier design, both elements hand-built
and installed within a substantial cabinet at the company’s Stroud-based production HQ.

New ATC sub-bass driver
The C4 Sub Mk 2 features the new SS75-314SC sub-bass driver, the first to be purpose-built for an ATC sub-bass system and developed by the R&D team to reproduce the lowest four octaves of the audio band. In order to achieve this the design exploits ATC’s signature short-coil/long-gap configuration to its natural limits with an exceptionally long 30mm magnetic gap, surrounded by a 6-inch/150mm N48M Neodymium magnet – the most powerful ever assembled by ATC and a first
for the company. In support, the wholly redesigned motor system features a new rubber roll- surround for high excursion capability, a new spider for optimised compliance geometry, and high flow motor venting for low noise and compression.

As well as minimising distortion, this unprecedented short-coil/long-gap configuration ensures the voice coil remains within the motor structure – even at high drive levels – maximising cooling, reducing power compression, and improving reliability. Turbulent air noise within the driver is minimised by a large, flared vent running through the centre of the motor structure, which has the added benefit of increasing voice coil and motor cooling.

Consequently, the C4 Sub Mk2 delivers an extended low-frequency response while avoiding electronic equalisation, 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 loudspeakers.

New 300W ATC amplifier

The all-new 300W class AB design is precisely optimised to the requirements of the new driver, resulting in fast, dynamic bass with minimal colouration. Two balanced line inputs provide connectivity for stereo or AV/home cinema systems while two balanced outputs are available to feed partnering ‘main’ stereo loudspeakers or to ‘daisy-chain’ multiple subs. Low-pass filters are analogue, 4th order Linkwitz-Riley, with filter frequency options ensuring optimal integration with partnering speakers. In addition, an industry-standard 80Hz low-pass filter and an ‘off’ option (for use with external processing) are joined by a polarity switch, variable 180° phase adjustment and a stepped attenuator over a 21 dB range for precise level matching.

The cabinet
Hand-built and finished at ATC’s cabinet factory and sharing styling with the brand’s ‘Classic’ and ‘Tower’ series loudspeakers, the C4 Sub Mk 2’s 70 litre cabinet employs 25mm/1-inch thick panels and heavy bracing. It’s available in standard Cherry, Black Ash, Walnut and Oak real-wood veneers, as well as Satin Black and Satin White finishes, or in premium Rosewood, European Crown Cut Walnut, Burr Magnolia and Pippy Oak real-wood veneers, with the option of high gloss over
veneers and black/white piano lacquers also available.

The size and performance of the C4 Sub Mk 2 make it a natural complement for ATC SCM19, SCM20, SCM40, SCM50 and SCM100 active/passive systems and high performance loudspeakers of a similar size. Multiple subs can be employed to further elevate performance in larger rooms or when partnering larger loudspeakers. Buffered linkable inputs and outputs make connection of multiple subs easy.

Designed and engineered with a focus on resolution and integration, the C4 Sub Mk2 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. It provides an upgrade path to customers owning smaller loudspeakers and lacking space for larger stereo loudspeakers whilst also strengthening ATC’s options in AV applications.

ATC C4 Subwoofer Mk2

Price and Availability

ATC C4 Sub Mk 2 typical UK retail prices (inc VAT)
Standard finishes: £3990
Premium finishes: £4750
Add high gloss over veneers: +£1979
Piano black/white: £6140