Sunfire True Subwoofer MKII

Description

The Sunfire True Subwoofer MKII is one of the landmark designs in the history of high-performance compact subwoofers. Developed by Bob Carver and introduced as an evolution of the original True Subwoofer, the MKII pursued an almost counterintuitive goal: deliver the deep, high-output bass normally associated with a large enclosure from an enclosure measuring only 11 inches on each side. Its combination of extreme amplifier power, long driver excursion, sophisticated protection circuitry, and a push-pull driver arrangement made it an unusually ambitious product for its era.

At the heart of the MKII is a 2,700-watt built-in amplifier incorporating Sunfire’s patented Tracking Downconverter power-supply technology. Rather than requiring a massive conventional power supply, the system dynamically supplies the amplifier with the energy demanded by the signal. The result is an extraordinary power-to-size ratio. The MKII employs opposed active and passive driver elements with approximately 2.35 inches of stroke, allowing it to move a remarkable volume of air despite its tiny cabinet. Contemporary specifications rated frequency response at approximately 18 Hz to 100 Hz, with output capability exceeding 110 dB under suitable conditions.

The MKII also addressed one of the original model’s quirks. The revised driver/passive-radiator balance reduced the tendency of the cabinet to physically move across the floor during demanding passages, while the MKII delivered somewhat greater maximum output. Secrets of Home Theater and High Fidelity measured an impressive 105.3 dB at 25 Hz in near-field testing before the limiters began operating. The reviewer also noted that the subwoofer remained remarkably free of audible boominess and praised its ability to add the lowest octave to both music and movie soundtracks.

The extensive rear-panel controls make the MKII adaptable to both two-channel and home-theater systems. The continuously variable phase control runs from 0 to 180 degrees, while the crossover can be adjusted from approximately 35 to 100 Hz. A high-pass output can also be used to relieve the main speakers of some low-frequency workload. The design incorporates limiting and clipping-protection circuitry, allowing the system to produce very high levels without the obvious distress often associated with small subwoofers being pushed beyond their limits.

Contemporary reviewers were enthusiastic about the engineering accomplishment. Audio described the cabinet as “minuscule for a subwoofer of its output and frequency range,” while The Audiophile Voice characterized the original concept as capable of “prodigious deep bass” from an extraordinarily small enclosure.

For music, the MKII is particularly interesting when used to supplement rather than overwhelm the main speakers. It can restore fundamental weight to pipe organ, synthesizer, orchestral bass drum, and the lowest piano notes while remaining physically unobtrusive. For home theater, its enormous output capability makes it equally suited to reproducing explosions, earthquakes, spacecraft launches, and other LFE effects.

The Sunfire True Subwoofer MKII remains a fascinating example of Bob Carver’s engineering philosophy: use amplifier technology, driver excursion, electronic control, and clever enclosure design to challenge the conventional relationship between cabinet size and bass performance. Even decades later, its 11-inch cube, 2,700-watt amplifier, and genuine sub-20-Hz capability make it an unusually memorable piece of high-end audio history.

Review Quotes

• “The engineering that went into this product is really amazing.” — Secrets of Home Theater and High Fidelity
• “Minuscule for a subwoofer of its output and frequency range.” — Audio
• “Prodigious deep bass” from an exceptionally small enclosure. — The Audiophile Voice

Product Specifications

• Type: Powered compact subwoofer
• Amplifier: 2,700 watts, built-in
• Power supply: Patented Tracking Downconverter
• Driver configuration: Opposed active/passive push-pull design
• Driver bore: 8 inches
• Driver stroke: Approximately 2.35 inches
• Air displacement: Over 235 cubic inches
• Frequency response: 18–100 Hz, approximately +0/–3 dB
• Crossover range: 35–100 Hz
• Crossover slope: 36 dB/octave
• Phase: Continuously adjustable, 0–180°
• Inputs: Line-level and speaker-level
• High-pass output: 70 Hz, 6 dB/octave
• Dimensions: 11 × 11 × 11 inches
• Weight: Approximately 48 lbs.
• Finish: Black