Released in 1969 by KEF, the original KEF Concerto (Model SP1004) was a landmark three-way bookshelf loudspeaker. Designed by founder and ex-BBC engineer Raymond Cooke, it brought high-end, wide-frequency home audio into a mainstream footprint before remaining in production until 1977.
 
Origins and Design
The Creator: Raymond Cooke founded KEF (Kent Engineering & Foundry) in 1961, applying pioneering acoustic testing and synthetic materials to transducer design.
Three-Way Configuration: The Concerto was notable as one of the very first compact/bookshelf enclosures to successfully implement a dedicated three-way system, featuring a dedicated midrange to untangle congested frequencies.
The Iconic Driver Lineup: It utilized KEF's legendary first-generation driver array: the famous B139 "racetrack" bass driver, the B100 midrange unit, and the T27 dome tweeter, backed by a hardwired passive crossover network.
DIY Kits: In addition to factory-assembled cabinets, KEF famously sold the Concerto components as enthusiast speaker-building kits, allowing audiophiles to construct matching enclosures using official KEF crossovers and driver specs.
 
 
 
Core Specifications
System Type: 3-way, bass reflex enclosure
Internal Volume: 62 liters
Nominal Impedance: 8 ohms
Power Rating: 30 Watts
Frequency Range: 30 Hz to 30,000 Hz (some technical sheets claim 25 Hz to 40,000 Hz)
Crossover Frequencies: 400 Hz and 3,500 Hz
 
Driver Complement
Bass Unit (Woofer): KEF B139 (A6171) – A unique, flat-faced elliptical/oblong polystyrene woofer (330 x 240 mm)
Midrange Unit: KEF B110 (A6362) – A 130mm Bextrene cone midrange housed in its own independent, sealed internal enclosure
Tweeter: KEF T27 (A6340 / SP1003) – A 19mm Melinex dome tweeter
 
Physical Dimensions
Cabinet Size (H x W x D): 711 x 432 x 305 mm (28 x 17 x 12 inches)
Weight: 22.7 kg (50 lbs) per speaker
Cabinet Finishes: Walnut (this model), teak, or white wood veneer with brown, grey (this unit), or beige grille cloth