The Acoustic Transducer Company (ATC) announced the C4 Sub Mk 2 active subwoofer system. The C4 Sub Mk 2 deploys the 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.

The C4 Sub Mk 2 features the new SS75-314SC sub-bass driver using ATC’s long-gap/short-coil configuration to its natural limits with a long 30mm magnetic gap, surrounded by a 6-inch/150mm N48M Neodymium magnet. As well as minimizing distortion, this short-coil long-gap configuration “ensures the voice coil remains within the motor structure – even at high drive levels – maximizing cooling, reducing power compression, and improving reliability.” Turbulent air noise within the driver is minimized by a “large, flared vent running through the center 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 equalization, 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.

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 integration with partnering speakers. In addition, a 80Hz low-pass filter and an ‘off’ option (for use with external processing) is joined by a polarity switch, variable 180° phase adjustment and a stepped attenuator over a 21 dB range for level matching.