Excellent condition and played at sane volumes! $400. Figure another $50 to cover shipping and PalPal fees. Here's a description from ML's site:
Abyss represents MartinLogan's ultimate Design Series subwoofer. Featuring a high-resolution 12-inch aluminum cone driver Abyss effortlessly provides exceptional bass. Performance aside, the real story is Abyss' innovative user-configurable design. Capable of both front- and down-firing operation and featuring flexible crossover controls Abyss is capable of providing superb bass from any location – whether in a corner, under or behind furniture, or even installed in a cabinet.
Low-Distortion Aluminum-Cone Driver
Abyss's high-resolution driver combines a 12-inch aluminum-cone diaphragm with a high-intensity magnet structure to achieve huge excursion and output capability without sacrificing detail. By eliminating cone flexure, even at long voice-coil excursions, aluminum diaphragms help our advanced-technology bass drivers achieve the very low distortion necessary for proper blending with MartinLogan electrostatic speakers.
Front-Firing or Down-Firing Option
To maximize performance when installed inside of a cabinet or other custom installation, Abyss's standard down firing configuration easily converts into a front firing configuration. A grill cover and 90° RCA adaptors are provided for use in front firing applications. When used in a down-firing configuration the grill can also be used to cover the connection panel.
Advanced Switching Amplifier
Abyss's amplifier belongs to recently developed class of switch-mode designs that incorporate a variety of innovative techniques to reduce noise, distortion, and heat to the lowest possible levels. In particular, the switching frequency is much higher than in typical subwoofer amplifiers of this type. It can produce a true 300 watts continuously.
Inverse Mathematical Equalization
An IME (inverse mathematical equalization) filter is derived from the inverse of the unfiltered driver response. Precision IME filtering yields extremely accurate low-frequency response – far superior to that provided by the simple second-order, high-Q filters typical of competitively priced subwoofers.
Seamless System Integration
Abyss's connections and controls are designed to enable easy, seamless integration with any stereo music or multi-channel home theater system. It's main left/right line-level inputs feed into a precision low-pass filter with a cutoff frequency variable from 30 to 80 Hz. For systems in which a surround processor supplies the crossover, Abyss provides an LFE input that completely bypasses its internal filters. It also has an unfiltered line-level output to allow operation of multiple subwoofers in a serial configuration.
Energy Transfer Coupler Spikes
The Abyss is supplied with sturdy, 1/4-20 MiniETC™ spikes, which can be used in place of the standard feet to enhance stability on thick carpets or to create tighter coupling between speaker and floor.
Although ports are a convenient and cost-effective way of increasing low-frequency output, they rely on resonant energy in a way that impairs bass quality. A good sealed system will exhibit less transient-blurring group delay while maintaining smooth, consistent response regardless of output level or voice-coil temperature. Listen carefully to the sound of a bass drum, and you'll hear the difference.