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A Modern Field Coil Driver

Field coils have been around for over 150 years, and were all but replaced entirely with plentiful and inexpensive permanent magnets in the 1950s. However in spite of being expensive and labor intensive to make, field coils are the superior magnet for sound reproduction. They provide a constant highly uniform gap density, and a magnetic stiffness that is hundreds if not thousands of times higher than a permanent magnet. That uniformity and stiffness translates into very high accuracy and low distortion, better in both respects than permanent magnets are capable of. They are also adjustable. Varying the power supplied to the field coil changes the Thiele Small parameters of the driver, and as a result tunes the character of its sound.

Modern field coils are a blend of the old and new. A powerful 1.7 Tesla electromagnetic motor is the central driving force behind our driver. The frame is a heatsink, drawing thermal energy away from the motor. The moving mass is constructed with soft leather surrounds, hand-wound copper-clad aluminum voice coils, and lightweight curvilinear mulberry fiber formers and cones. The shape, weight, and material of the cones contribute to high sensitivity, an excellent combination of transducer speed and damping, full range response, and off-axis performance. The patented spider design holds the voice coil in tension with a flexible, acoustically transparent lattice and a carbon fiber composite collar, ensuring accurate, linear cone motion and no unnecessary resistances to the music signal whatsoever. The Type D dipole version of our driver takes advantage of the acoustically transparent spider to include a rear-firing whizzer, only one of its kind in the world. This provides phase coherent presentation across the full frequency range in both the front and rear of the driver.

The S1 and S2

The S1 loudspeaker minimally compensates for natural cabinet diffraction, and nothing else. The signal isn't needlessly degraded, as no filters or crossover circuitry are necessary. It simply holds the driver at ear level, where it plays with perfect phase and timing, free of coloration, and port tuned for deep, accurate bass. The S2 is a product of years of intensive development. It suspends the Type D field coil driver almost wholly in free space, attached at a single point to a layer-constrained, high mass, hardwood and glass-filled nylon mount for excellent imaging and clarity. Its Acoustic Elegance LO15 dipole woofer is "port constrained" on the front side to lower resonant frequency and raise efficiency. The baffle is folded into a discrete, open chamber in the back, which greatly reduces sound wave cancellations common in dipole applications, and delivers full and yet unmistakably dipole bass response.