Bowers & Wilkins DB4S Active Subwoofer Rosenut

The DB4S is the most compact subwoofer in the Bowers & Wilkins DB Series, designed to deliver the same engineering philosophy as the larger DB1D, DB2D, and DB3D in a more room-friendly enclosure. Where the DB1D and DB2D employ dual-opposed driver configurations for force cancellation, the DB4S takes a single-driver approach with a front-firing 250mm (10in) Aerofoil cone bass unit — the same driver technology found throughout the DB range and the 700 Series loudspeakers it is designed to complement.

Aerofoil Cone Technology

The Aerofoil cone at the heart of the DB4S uses a variable-thickness profile engineered for maximum rigidity with minimal mass. Unlike conventional flat or uniformly curved cones, the Aerofoil shape is optimised so that each section of the cone is precisely the thickness it needs to be to resist bending and flexing at the frequencies it handles. This approach allows the cone to maintain pistonic behaviour deeper into its operating range, reducing distortion and delivering tighter, more controlled bass than a conventional driver of the same diameter.

Amplification and DSP

Driving the Aerofoil cone is 1000W of Class D amplification supplied by Hypex, a specialist in high-efficiency amplifier modules widely used in professional and high-end domestic audio. The digital preamplifier incorporates Dynamic EQ, which continuously optimises the frequency response to maintain balanced bass output regardless of volume level. This ensures the subwoofer sounds authoritative at low listening levels without becoming boomy or uncontrolled at higher volumes.

Control and Connectivity

The DB4S is configured entirely via the Bowers & Wilkins smartphone app over Bluetooth Low Energy (BT-LE) — there are no physical controls on the subwoofer itself. The app provides access to crossover frequency, phase, EQ presets, and volume, along with a calibration routine for room correction. Signal connectivity includes two balanced XLR inputs, two unbalanced RCA inputs, and two 3.5mm inputs. For integration with home automation systems, the DB4S offers a 12V trigger input and an RS-232 port via a 9-pin D connector. The subwoofer includes auto-sensing power management, switching on when it detects an audio signal and entering standby (less than 0.5W) after approximately 20 minutes of silence.

What the Press Says

• "Great sound" and "superb calibration controls" — What Hi-Fi? (March 2021)