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T-Bolt III subwoofer

as reviewed by Karl Lozier







Genesis G-6.1 with integral dual Servo controlled 12" subwoofers each cabinet.

Herron VTSP-2 (tubed) preamplifier. Pair of Herron M-150 (solid state) amplifiers. Herron VTPH-1MM phonostage.

Allen Wright's VSEI level 5 Modified Sony 9000ES SACD/CD. VPI – Mk II mounted with SME IV Tonearm + Grado Reference cartridge.

Interconnects: Kimber Select KS 1030, KS 1021/Herron Special. Power cords: Kimber PK-10 Palladian/Purist Audio Dominus. Loudspeaker cables: Kimber Select KS 3038, KS 3035/DiMarzio Super M-Path.

IsoNodes, SSC pucks, Iso-Blocks, Denon CDR-W1500 CD/HDCD player/recorder, Front-end components fed by Shunyata Hydra 8 power conditioner and FIM 880 AC power receptacle. Welborne Labs X1 Gatekeepers.


This T-Bolt III is the latest incarnation of Carl Marchisotto's subwoofer based on the principles used in the woofer towers of his Grand Reference system. Marchisotto claims no secret formula. His primary goal was to design the lightest possible cone while maintaining resistance to flexing, bending, or breakup. This should equate to accurate piston movement. Marchisotto adds a high-quality class AB amplifier to accurately control the cone's movement, and decided that an exactingly designed, vented enclosure offered very real advantages. These include a reduction in cabinet size, which is now about sixteen inches wide and high and roughly twenty inches deep.

In this latest (and possibly last) update, the port has been moved from the front panel to the bottom of the cabinet. According to Carl, what is more important is that the port is now double-flared, as it is in his woofer towers. When I told him that the Mk III version sounded noticeably cleaner and better in the deep bass and mid-bass, he replied that this was essentially due to the new port design. There have been no other significant changes, as he has not been able to improve anything else. There is one esthetic change available as an option—a beautifully grained, lightly stained finish on natural ash. As hard to describe as the sound of a loudspeaker system, that finish has a subtle golden glow. Though the grille cloth is black, I can personally attest to the ease in changing the grille cloth to match any décor, or the cabinet itself.    

Subwoofers are typically used to cover the bass range below 60, or perhaps 50 Hertz, where even very expensive loudspeakers that feature six-inch (or smaller) woofers cannot produce sufficient high-quality bass response for musical enjoyment (though this may not apply to listeners who stick to chamber music or vocals). The octave between 60 Hertz and 30 Hertz is extremely important for full musical enjoyment, and certainly for show-off movie soundtracks.

Placement is exceedingly important for best performance in the lower frequencies. Try a corner placement if it is available within six feet or so of the main loudspeakers. When setting the output level or roll-off frequency, start by listening to a well-recorded baritone voice. It should not change when adding the subwoofer.

As a result of the light, well-controlled cone, the T-Bolt III offers fine, clean response far above the deep bass range, so it can mate with even the smallest loudspeakers. Marchisotto's dealers report that it mates particularly well with speakers (such as electrostatic, ribbon, and planar types) that are notoriously difficult to blend with subs. I found the response above the deep bass range to be extremely good. I certainly have not heard a better subwoofer in my home. At no time was I able to hear any hint of trouble with a pair of these subs, even at extremely loud listening levels. The bass range was clean, clear, and detailed. I could not ask for more or better in that important 30-to-60-Hz octave. In the relatively rare range below 30Hz, the T-Bolts continued to respond, but lacked the power and authority of competitors at double their price, which may have larger cabinets but do not provide the clean and fast response of the T-Bolt III.

I now use the T-Bolt IIIs in my home theater system, in a room about 32 by 14 feet, and have never been less than completely satisfied. Moderate size, extreme control flexibility, plus automatic on/off add to the impressive performance of the T-Bolt IIIs for music or home theater listening. Karl Lozier


  • System Type: Powered, front firing ported subwoofer - Front firing allows it to be placed in various locations, such as in a cabinet, without affecting performance.

  • Driver Diameter: 12 inches - We developed a unique driver with the attack speed of a small woofer and the very deep bass of a large one.

  • Driver Construction: A blend formulation consisting of both natural and synthetic fibers Highly rigid with lower mass than Kevlar, aluminum, magnesium or titanium drivers.

  • Response: 20Hz to 160Hz - We roll off the response below 20Hz to eliminate spurious low frequency noise found in some digital discs.

  • Crossover Frequency: Continuously variable low pass 40Hz to 160Hz, fixed high pass 100Hz. - The wide range, low pass crossover allows proper integration with a wide range of large and small speakers.

  • Phase: Continuously variable from 0 to 180 degrees - Allows subwoofer's sound wave to properly integrate with loudspeaker, independent of room placement.

  • Power:Manual or auto on/off, detachable power cord, 120 or 240 Volt operation
    Sensing circuit allows subwoofer to be automatically powered on and off by preamplifier or receiver.

  • Amplifier: Fully discrete Class A/B outputs - Wattage output is ample enough to provide more low-end impact than any competitor's subwoofer.

  • Finish: Black or cherry wood veneer - The cabinet is handcrafted to very high wood finishing standards to compliment the finest of furnishings.

  • Cabinet Size: 16" H x 16"W x 18"D (20"D with allowance for grille and power cord) - Small size allows for ease of placement in any room.

  • Weight: 85 lbs.

  • MSRP: $1795

T-Bolt III
Retail: $1795