Cambridge Audio MSX Sub 300 black

Successor to the Minx X301, the MSX Sub 300 follows the proven formula: a 20 cm driver paired with a passive radiator (ABR), driven by a 300 W amplifier and an integrated DSP. Cambridge Audio has revised the design, modernised the finish and integrated this subwoofer into its new modular MSX range, designed for installations where space is just as important as sound quality.

A compact form factor for 300 watts

Measuring 266 × 315 × 278 mm and weighing 7.5 kg, the MSX Sub 300 remains surprisingly small for a subwoofer housing an amplifier of this power. The sealed enclosure uses an active 20 cm (8-inch) driver paired with a passive radiator of the same diameter: this ABR (Auxiliary Bass Radiator) configuration allows the unit to reach low frequencies without the need for a port, which limits air turbulence and reduces the size of the enclosure. The result is bass that reaches 31 Hz at -6 dB, a respectable figure for such a compact volume.

The matte finish, available in black or white, fits in with the aesthetic of the MSX range and Cambridge Audio’s recent products. The subwoofer can be tucked beside a piece of furniture, placed under a coffee table or positioned in a corner without drawing attention.

DSP in the service of precision

Digital signal processing is the real backbone of this subwoofer. The DSP analyses and corrects the signal in real time to maintain precise, controlled bass, even at high volumes. Cambridge Audio uses this approach across both MSX subwoofers to avoid the classic pitfall of small subwoofers: bloated, sluggish bass that muddies the rest of the frequency spectrum.

Manual adjustments complement this work. The crossover frequency is adjustable from 50 to 200 Hz, making it possible to fine-tune the blend with satellite speakers, whether the MSX10 and MSX20 or other models. The phase control, variable from 0° to 180°, helps synchronise the subwoofer with the main speakers depending on its position in the room. These two parameters, often overlooked on entry-level and mid-range subwoofers, make a noticeable difference to the coherence of the overall sound.

Integration into an existing system

The connectivity is straightforward: a stereo RCA input (line level) and an RCA pass-through output. This output allows a second subwoofer to be chained if the room requires it, or the signal to be sent to another device. There is no high-level connection (speaker terminals) or digital input: the MSX Sub 300 is aimed at amplifiers and receivers with a dedicated subwoofer output or usable pre-outputs.

In terms of compatibility, Cambridge Audio positions it primarily as a natural complement to the MSX10 and MSX20 speakers in 2.1, 5.1 or larger configurations. But there is nothing to stop it being paired with other compact or floorstanding speakers, as long as the upstream amplifier handles bass filtering correctly. The Cambridge Audio CXA61, CXA81 and EXA100 amplifiers offer a subwoofer output and flexible connection management. The automatic standby mode cuts power in the absence of a signal, a practical detail when the subwoofer remains permanently connected.

From the living room to the home theatre

With 300 W of power and a reach down to 31 Hz, the MSX Sub 300 covers a wide range of uses. For stereo music listening, it adds body and weight to small speakers, which often struggle below 80 Hz. In a home theatre setup, it reproduces the low-frequency effects of soundtracks with enough impact for medium to large rooms (approximately 15 to 30 m²), without claiming to rival 25 or 30 cm subwoofers in very large spaces.

The modular concept of the MSX range allows you to start with a pair of satellite speakers and add the subwoofer later, or to begin directly in 2.1 and build towards a surround system over time. This progressive approach is one of the system’s key strengths.

What sets the Sub 300 apart from the Sub 200

The two MSX subwoofers share the same philosophy, but not the same size. The Sub 200 houses a 16.5 cm (6.5-inch) driver and a 200 W amplifier: it is suited to small rooms and installations where space is very limited. The Sub 300, with its 20 cm driver and 300 W, offers greater bass extension, more power in reserve and a better ability to fill a larger space. If the room exceeds 15 m² or if home theatre is a primary use, the Sub 300 is the more relevant choice of the two.

Technical Specifications

Cambridge Audio MSX Sub 300

Speakers and Acoustic Performance

• Type: active subwoofer
• Power: 300 W
• Speakers
  • 1 x 20 cm active
  • 1 x 20 cm passive radiator
• Frequency response: 31 Hz (-6 dB) – 200 Hz

Signal Processing and Settings

• Signal processing: built-in DSP (digital signal processing)
• Real-time DSP bass optimisation
• Active filter (crossover): adjustable from 50 to 200 Hz
• Phase control: variable (0° to 180°)
• Automatic standby

Connectivity

• Inputs
  • 1 x stereo RCA input (line level)
• Outputs
  • 1 x RCA pass-through output

Design and Integration

• Compact format suited to living rooms and home theater installations
• Premium matte finish
• Available colours: matte black, matte white
• Designed to integrate with the MSX range and hi-fi / home theater systems

Dimensions and Weight

• Dimensions (W x H x D): 266 x 315 x 278 mm
• Weight: 7.5 kg

Box Contents

• 1 x MSX Sub 300 subwoofer
• Power cable
• Quick start guide
• Safety guide
• Registration card