91%

ATC C4 Sub Mk2

Name: ATC C4 Sub Mk2
Brand: ATC
SKU: c4-sub-mk2
Rating: 4.6 (25 reviews)

View at ATC

Built-in Power Amplifier

Balanced Output

XLR Input

Gain Switching

C4 Sub Mk2 | 12" SUBWOOFER

Hand-built in England, the ATC C4 Sub Mk2 is a high-performance active subwoofer, engineered to deliver professional studio quality sound to the home environment. Designed to integrate seamlessly into an existing audio system, its features have been carefully considered and its proprietary drive unit and active amplifier are designed to work together to reproduce the lower octaves of the audio band without compromise.

At its core is the SS75-314SC 12” (314mm) drive unit, meticulously engineered in-house by ATC to accurately reproduce sound below 160Hz. Its short coil operates within a very long magnetic gap to ensure minimal distortion across the full dynamic range, guaranteeing the highest quality audio experience.

The C4 Sub Mk2's active design integrates the driver and a 300W Class A-B MOSFET based power amplifier into a single system, ensuring peak performance. User controls allow for optimised integration with existing loudspeakers, delivering the same exceptional sound quality found in the world's top music and film recording studios.

Dealers selling ATC near you

Join us at T.H.E. Show SoCal 2026!

Overall Score 91/100

Deliciously Crispy

The ATC C4 Sub Mk2 delivers extended low-frequency reach and remarkably low distortion, driven by a new 12" SS75-314SC and 300W Class‑AB amp for punchy, fast dynamic bass. Reviewers at Audioholics and Alpha Audio praise its studio-grade build and seamless integration with mains, though it demands careful room tuning.

Audioholics

"The C4 Sub Mk 2 promises studio-quality bass thanks to a new 12-inch driver and 300-watt Class AB amp."

Alpha Audio

"However, we almost have to tame the C4; this is truly a beast!"

The Ear

"Consequently, the C4 Sub Mk2 delivers an extended low-frequency response while avoiding electronic equalisation, unlike many subwoofers available today."

Pros

Deep, clean bass down to ~22 Hz with high SPL capability (tight, extended low end).
Fast, dynamic response and very low distortion from the SS75-314SC driver paired with the 300W Class‑AB amp.
Studio-grade construction and integration: hand-built, heavily braced cabinet and analogue Linkwitz‑Riley filters for seamless blending with mains.

Cons

Premium price and positioning — aimed at serious enthusiasts and pros rather than budget buyers.
High output can be overwhelming in small rooms; requires careful placement and tuning to integrate correctly.
Pro-oriented connectivity (balanced XLR I/O) — no consumer RCA inputs.

Sound Quality

91/100

Bass

92/100

Reviews consistently report deep, powerful bass down to ~22 Hz (Alpha Audio: "Frequency range 22 Hz", Audioholics/The Ear: "extends the low-frequency response down to 22 Hz") and describe it as a "beast" that can make floors vibrate. ATC's new SS75-314SC driver and 70‑litre cabinet are credited for tight, extended low end; reviewers note it avoids excessive coloration while delivering substantial output (116 dB peak).

Dynamics

90/100

Reviews highlight fast, dynamic performance and low distortion: ATC's short-coil/long-gap motor and optimized 300W Class‑AB amp are said to produce "fast, dynamic bass with minimal colouration" and reduce power compression. Reported SPL headroom (110 dB continuous, 116 dB peak) and reviewers' notes about impactful movie playback confirm strong macro- and micro-dynamics.

Show Less

Integration

93/100

Multiple reviews describe outcome-level integration: Alpha Audio says a properly tuned C4 can be "inaudible" and "disappears," blending "seamlessly with the mids and treble," while The Ear highlights reduced phase shift/group delay aiding integration. Audioholics likewise notes ATC's design focus on "resolution and integration," supporting high marks for real-world blend with mains.

Build Quality

93/100

Build is described as studio-grade: hand-built cabinet with 1" thick panels, heavy bracing, and a robust motor assembly (The Ear, Audioholics). Reviewers note the unit is "big and heavy" (42 kg) with premium magnetic and venting design, supporting a high score for construction and durability.

Features Connectivity

90/100

Feature set is professional and usable: balanced inputs/outputs for daisy-chaining, 4th-order Linkwitz‑Riley analog low-pass options (50/65/80/320 Hz + 80 Hz industry standard), phase and polarity controls, stepped attenuator and limiter. Reviewers emphasize studio-friendly connectivity and analog controls that simplify precise matching to mains.

Value for Money

80/100

Price positioning is premium (review prices range widely; Audioholics lists $5,999; UK pricing reported between £3,990–£6,140). Reviewers praise performance and build but stop short of calling it an unequivocal "no-brainer"; suggestions to audition at home imply strong but specialist value for those seeking studio-quality, not a mass-market bargain.