Cambridge Audio MSX Sub 300 Subwoofer

The Cambridge Audio MSX Sub 300 is a compact active subwoofer that pairs an 8-inch driver and matching passive radiator with a 300-watt amplifier, reaching down to 31Hz for larger rooms and bigger soundtracks. It is the more powerful of the two MSX subwoofers, with DSP that keeps deep bass controlled rather than boomy as the level climbs.

Key Features of the MSX Sub 300

• Dedicated 300W Amplifier: More power for larger rooms and higher output.
• 8-Inch Active Driver with Passive Radiator: A larger driver and matching passive radiator move more air for deeper, fuller bass.
• Reaches 31Hz: Extension into the bottom octave for cinematic low frequencies.
• Onboard DSP: Keeps the deepest notes controlled as the volume rises.
• Variable Crossover: Adjustable from 50 to 200Hz to match the roll-off of your main speakers.
• Variable Phase: 0 to 180 degree control time-aligns the sub with your speakers for tighter bass.
• Auto-On: Powers up with signal, sleeps when idle.
• Built for Larger Spaces: The sub to choose when the room is too big for the Sub 200.
• RCA Input and Pass-Through: Connects to any subwoofer or preamp output and forwards the signal on.
• Two Matte Finishes: Matte black or matte white to match the MSX speakers.

300 Watts for Larger Rooms

The Sub 300 steps up from the Sub 200 with a bigger amplifier and a larger driver, the combination Cambridge Audio recommends when a room is too large for the compact sub to fill comfortably. The extra 100 watts and the move to an 8-inch driver give it more headroom and deeper reach, so it can pressurize a bigger space without straining. The tuning philosophy carries over unchanged: scale and authority, but always under control rather than loose and overbearing.

8-Inch Driver and Passive Radiator

An 8-inch active driver works with a matching 8-inch passive radiator to move significantly more air than the Sub 200's 6.5-inch array. The passive radiator is an undriven cone energized by the active driver through the cabinet, reinforcing the deepest notes without a port and the noise a port can make at high output. That is how the Sub 300 reaches 31Hz cleanly and stays composed when a soundtrack calls for real low-frequency weight, rather than collapsing into a boom.

DSP Keeps the Bottom Octave in Control

Digital signal processing manages the driver so the deepest bass stays defined as you push the level. By shaping output and frequency response on the fly, the DSP lets the Sub 300 chase low-end impact without losing grip, which is what separates a sub that adds atmosphere from one that just muddies the room. It is the same approach as the Sub 200, scaled up to match the bigger driver and amplifier.

Blending the Sub 300 With Your Speakers

The Sub 300 gives you the same integration controls as its smaller sibling, which matter even more as output goes up. The variable crossover, from 50 to 200Hz, sets where the subwoofer takes over from the main speakers, while the variable phase control, sweeping 0 to 180 degrees, aligns the sub with those speakers for a clean blend rather than a smeared one. Spend a few minutes here and the Sub 300's output feels like an extension of your speakers, not a separate source of bass.

A Compact Cabinet in Two Finishes

Even with the larger driver, the Sub 300 stays manageable at roughly a foot tall, so it fits rooms where a traditional floor-shaking subwoofer would dominate. Matte black and matte white finishes match the MSX satellites and Cambridge Audio's L/R active speakers, keeping a larger system visually consistent.

Connections and Setup

The Sub 300 takes a low-level RCA input from a subwoofer output, an AV receiver's sub pre-out, or a stereo preamp, and offers an RCA pass-through to feed another component. Auto-on brings it up when it senses a signal and returns it to standby when the room goes quiet. Setup is straightforward: one cable, then level and crossover dialed in, with phase set to taste and the sub handling its own power.

More in the Cambridge Audio MSX Series

The MSX Sub 300 is the larger, more powerful subwoofer in Cambridge Audio's MSX modular range.

• MSX Sub 200 - The more compact active sub for smaller rooms.
• MSX10 - The compact satellite the Sub 300 partners in a modular system.
• MSX20 - The larger dual-driver satellite.

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Cambridge Audio MSX Sub 300 Specifications