1986 to 1997 – 12,000 units Quad 99 - 1999 to 2002 Stereo Power Amplifier Quad 303 – 1967 to 1985 – 94,000 units Monobloc Power Amplifier Quad 50E - 1966 to 1983 - 12,000 units Current Dumping Power Amplifiers Quad 405 – 1975 to 1982 – 64,000 units Quad 405–2 1982 to 1993 – 100,000 units Quad 306 – 1986 to 1995 – 25,000 units Quad 606 – 1986 to 1997 – 27,700 units Quad 707 - 1997 to 1999 Quad 909 - 1999 to 2002 Integrated Amplifier Quad 77 - 1994 to 1999 Loudspeakers In late 1949 (or early 1950), the company launched the CR corner ribbon loudspeaker. This used a Goodmans Axiom 150 cone loudspeaker for the lower frequencies and an electromagnetic ribbon loudspeaker, designed by Acoustical, for the higher frequencies. Fewer than one thousand units were sold. In 1957, they released the Quad Electrostatic Loudspeaker (ESL), the first production full frequency range electrostatic loudspeaker renowned for sonic transparency and very low distortion. Its sonic neutrality and transparency were offset by its extreme directionality, moderate power handling, the need for a large room, and moderate bass extension; its novel electrical characteristics could render some amplifiers unstable, which could result in damage to either or both. The ESL was quickly adopted by the BBC for monitoring the sound quality of their broadcasts. The BBC eventually replaced them with moving coil based monitor speakers developed by several manufacturers, such as the highly successful LS3/5A, that were more easily transported and stored, and were more representative of typical contemporary hi-fi speakers. Quad launched ESL-63, successor to the original ESL, in 1981. The newer design featured larger panels and an innovative stator design, made up of eight concentric rings fed from the centre outwards through analogue delay lines, so that the audio signal radiated out as though emanating from a single point. Subsequent electrostatic models, the 988/989, the 2805/2905 and then the 2812/2912 were successive refinements of the ESL-63 design, featuring increased power handling and output levels, more sophisticated overload protection, and greater structural rigidity. Following the Verity acquisition, Quad developed and market a range of conventional electrodynamic loudspeakers alongside its electrostatic line, available in both passive and active (i.e. featuring in-box amplification) configurations. Many of Quad's products, including the Quad Electrostatic Loudspeaker (ESL-57), are still serviced by the Company's Service Department in Huntingdon. References External links http://www.iaggroup.com/ https://web.archive.org/web/20150811030914/http://www.iaggroup.com/quad1.html https://web.archive.org/web/20150228214406/http://www.iaggroup.com/WHARFEDLE.html http://www.fidele.co.uk/