Sonus Faber Gravis VI walnut

Sonus Faber Gravis VI, the sealed subwoofer from the Reference collection

Reaching down to 18 Hz without the bass becoming bloated is the goal of the flagship Gravis subwoofer range. Sonus Faber has been working on the subject for a long time: its first subwoofer, the Gravis FB100, dates back to 1986. The Gravis VI extends this expertise to complement speakers from the Reference collection, with two 320 mm drivers in a sealed enclosure and 1700 watts of continuous amplification.

Two 320 mm drivers in a sealed enclosure

The Gravis VI’s acoustic foundation is based on two 320 mm (12-inch) long-excursion drivers, fitted into an airtight cabinet. This sealed-enclosure design, rather than a ported bass-reflex tuning, prioritizes bass control and transient precision: the subwoofer releases less unwanted energy and follows the rapid attacks of a double bass or a soundtrack explosion more accurately. In return, a sealed enclosure reaches slightly less deep than a similarly sized vented cabinet, a compromise Sonus Faber offsets with the radiating area of two large drivers and the available power.

Each diaphragm is a three-layer sandwich cone: two layers of woven synthetic fibers surround a Nomex honeycomb core. This structure remains rigid without weighing down the moving assembly, allowing it both to move a great deal of air and retain control of movement. The wide rubber surround allows the large excursions required for the very lowest frequencies.

By default, response extends down to 18 Hz at the -6 dB point, with a fourth-order Linkwitz low-cut slope. The Gravis VI therefore reproduces the infrabass that most floorstanding speakers leave aside, while the upper limit (the crossover frequency) remains adjustable according to the speakers with which it is paired.

1700-watt Class AB amplification

The built-in amplification operates in Class AB and delivers 1700 watts RMS, with peaks of 2400 watts. Class AB is not the most common choice for active subwoofers, where Class D dominates due to its efficiency: Sonus Faber instead favors linearity and a certain warmth in the bass here, even if it means dissipating more heat. The power reserve is especially useful in large rooms and during dynamic peaks, when two 320 mm drivers demand current without weakening.

Fine adjustment from the app

All setup is handled through a dedicated app, available for iOS and Android. It allows continuous adjustment of the crossover frequency between 40 and 150 Hz, with a 24 dB-per-octave slope, to define the precise point at which the Gravis VI takes over from the speakers. Phase can be adjusted across a full 360 degrees, enough to align the subwoofer with the main speakers even in challenging configurations.

The app also provides access to adjustable delay from 1 to 20 milliseconds, useful for synchronizing bass with the rest of the system or with a second subwoofer, as well as a parametric equalizer offering up to eight filters. These filters, combined with automatic room calibration, correct the peaks and dips that the room inevitably imposes on bass, where an unadjusted subwoofer begins to boom on certain notes. Four presets store different uses, and the main volume remains directly accessible on the subwoofer.

Three inputs for all systems

The Gravis VI accepts three types of connection. The two unbalanced RCA inputs receive a line-level signal, left and right channels or an LFE channel, as supplied by a home theater processor. The two balanced XLR inputs are suitable for long cable runs and high-end preamps, where balanced operation limits interference pickup. The high-level input, on a four-pole Neutrik Speakon connector, connects directly to the amplifier’s speaker terminals: the subwoofer then receives the same signal as the speakers and retains the amplifier’s sonic signature.

Automatic standby and wake-up, with an adjustable threshold, prevent the electronics from remaining powered on continuously. To avoid using a signal cable, Sonus Faber optionally offers a wireless transmitter, the Gravis Transmitter, compatible with the Gravis III, V and VI.

Square cabinet, leather and lacquered wood

Beneath its finely crafted exterior, the Gravis VI remains an imposing object. The square cabinet is topped with a hand-finished wood or high-gloss lacquer panel, including a red finish with grain oriented at 45 degrees, while the sides are clad in black leather and enhanced with aluminum. The brand has matched the subwoofer’s aesthetics to those of the speakers in the Reference collection, so that it integrates into a system without looking out of place.

The weight speaks for itself: 52 kg per unit, measuring 616 mm high, 448 mm wide and 585 mm deep. This mass contributes to the cabinet’s inertia, so it moves all the less when the drivers push hard. A rubber isolation pad decouples it from the floor. The Gravis VI is sold individually: one is enough to fill a room, but installing two subwoofers distributed in different locations often smooths bass response more effectively.

Technical specifications

System

• Type: dual-driver active subwoofer, sealed enclosure
• Drivers: 2 long-excursion Ø 320 mm woofers, honeycomb sandwich cone, wide rubber surround

Acoustic performance

• Frequency response: 18 Hz to Fc (continuously adjustable by the user), at −6 dB, 4th-order Linkwitz acoustic filter, default setting

Amplification

• Built-in amplifiers: high-performance Class AB
  • RMS power: 1700 W
  • Peak power: 2400 W

Power supply

• AC input voltage: 100 – 120 Vac – 50 / 60 Hz or 220 – 240 Vac – 50 / 60 Hz, factory selected
• Power consumption:
  • Standby: < 2 W
  • Rated power: 2100 W
• Fuse:
  • T12A H250V (100 – 120 Vac – 50 / 60 Hz)
  • T6.3A H250V (220 – 240 Vac – 50 / 60 Hz)

Connectivity

• 2 unbalanced line inputs (LINE), left and right / LFE channels, RCA connectors
• 2 balanced line inputs (LINE), XLR connectors
• 1 high-level input (HIGH LEVEL), Neutrik Speakon© 4-pole connector

Controls and operation

• Direct access to main volume (Master)
• Control via dedicated app:
  • 4 selectable presets
  • Volume adjustment
  • Continuously adjustable crossover frequency from 40 to 150 Hz, 24 dB / oct filter slope
  • Continuously adjustable signal phase from 0° to 360°
  • Up to 8 parametric equalization filters
  • Adjustable delay from 1 to 20 ms
  • Automatic room calibration
  • Automatic power on / off with selectable threshold

Cabinet and finishes

• Square-shaped cabinet
• High-gloss lacquered wood
• Black leather
• Aluminum

Isolation

• Isolation system: rubber pad

Dimensions and weight

• Product dimensions (H x W x D): 616 x 448 x 585 mm per unit
• Packaged dimensions (H x W x D): 810 x 600 x 725 mm per unit
• Net weight: 52 kg per unit
• Packaged weight: 60 kg per unit

Documentation

• User manual
• Quick start guide
• Firmware update