Magnavox Duode 33

The Duode 33 was introduced by Benjamin Electric Ltd. in 1936 as a Magnavox loudspeaker employing the patented dual-element voice-coil system developed by A. Cecil Barker. The design used two mechanically and inductively coupled coil elements to improve high-frequency response while maintaining low-frequency efficiency. Barker's invention was described in detail in Wireless World (6 March 1936), where the associated patents were credited to him. The commercial loudspeaker was manufactured by Benjamin Electric Ltd. through its Magnavox Speaker Section under the direction of Burgess Dempster.

The name "Duode" was not Barker's patent but a trademark registered by Benjamin Electric Ltd. for loudspeakers in 1936. Advertisements published in 1937 promoted the model as the Benjamin Duode Thirty-Three, manufactured under Magnavox patents and registered designs. The Duode 33 therefore represents a collaboration in which Barker supplied the patented loudspeaker principle while Benjamin Electric owned and marketed the Duode trademark.

Specifications

• Type: Electrodynamic loudspeaker
• Voice-coil impedance: 15 Ω
• Field supply: 6-30 W, optimum 12 W
• Power handling: 7 W maximum
• Recommended amplifier power: 2 W minimum domestic use
• Transformer: Integral output transformer, 65 mA primary rating
• Special features: Barker dual-element ("Duode") voice-coil system, hum-neutralising coil, high-inductance field coil, extended frequency response to approximately 15 kHz.

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