SW63

About the SW63

The Gradient SW-63 is a Finnish-made dipole subwoofer specifically designed to mate perfectly with the Quad ESL-63 electrostatic speakers. Introduced in 1991 and manufactured until 1999, it was the first Quad product not designed or made by Quad itself. The SW-63 features two 300mm long throw woofers in a dipole configuration housed in a cabinet that also raises the Quad ESL-63 to a more optimal listening height. It includes an active electronic crossover with bass level and midrange tone adjustments, fixed at a crossover frequency of 115 Hz, extending the system's frequency response down to 28 Hz (-3dB). The subwoofer requires a second stereo power amplifier to drive it, with selectable impedance options of 4 or 16 ohms. Recommended amplifier power ranges from 50 to 250 watts. The system is praised for its seamless integration with the Quad ESL-63, allowing higher sound pressure levels without distortion and maintaining the unique dipole radiation pattern. Dimensions are 66 x 47.5 x 28.5 cm (WHD), weighing 18.5 kg, and available with black or brown grille cloth finishes. The SW-63 remains highly regarded as part of one of the best speaker systems of all time.