Reference Series Model 104 (1973-76) and 104aB (1976-80)

In the early 1970s KEF invested heavily in digital technology to assist in the design and manufacture of loudspeakers. Using computers to control acoustic measurements allowed data to be stored in a form that significantly aided the design process as well as forming the basis of an advanced production quality control system. The first loudspeaker to benefit from this was the first of the new Reference Series, the Model 104.    
 
Model 104 was an 8 inch two-way system with an passive radiator augmenting the low frequency response, a format that was developed previously for the Cadenza system. The B200 bextrene coned bass driver for the 104 had a short coil/long gap magnet system for low distortion and the system included a three position acoustic contour control, which allowed +/-2dB of midrange level adjustment.  
 
In 1976 the system was updated into the 104aB, where aB was an abbreviation for ‘acoustic butterworth’, relating to the shape of the acoustic response of the midrange and treble drivers in the crossover region. Perfect integration of the units will only happen if the acoustic responses of the two units conform to a precise characteristic. Previously, crossover filters had been designed primarily on the basis of the electrical response of the filter but, in reality, the acoustic roll-off is also a function of the natural roll-off of the driver response. By considering the filter and driver as a combined system the filter response can then be optimised to give the precise acoustic roll-off necessary for perfect integration.
 
Specification: Model 104
System type: Two-way, stand-mount
Enclosure type: Passive radiator
Size: 630 x 330 x 260 mm (24.8 x 13 x 10.23 inches)
Weight: 15.8kg (34.75 lb)
Input Impedance: 8 ohms
Rated maximum power: 50W programme
Amplifier Requirements: 15-50 watts per channel into 8 ohms
System resonance: 35Hz, mechanical reflex
Frequency range: 30-30,000Hz
Frequency response: 50-20,000Hz +/-2dB
Sensitivity: 12.5 watts for 96dB at 1m and 400Hz in anechoic conditions
Crossover Frequency: 3000Hz
Finishes:  Walnut, Teak, White
Grille: black microcellular foam
System: SP1038
Drive units: B200 bass unit (SP1039), BD139 passive radiator (SP1042), T27 tweeter (SP1032)
Crossover: SP1041
 
Specification: Model 104aB
System type: Two-way, stand-mount
Enclosure type: Passive radiator
Size: 630 x 330 x 260 mm (24.8 x 13 x 10.23 inches)
Weight: 16.3kg (36 lb)
Input Impedance: 8 ohms
Rated maximum power: 100W programme
Amplifier Requirements: 15-100 watts per channel into 8 ohms
System resonance: 35Hz, mechanical reflex
Frequency range: 30-30,000Hz
Frequency response: 50-20,000Hz +/-2dB
Sensitivity: 12.5 watts for 96dB at 1m and 400Hz in anechoic conditions
Crossover Frequency: 3000Hz
Finishes:  Walnut, Teak
Grille: black microcellular foam
System: SP1038
Drive units: B200 bass unit (SP1039), BD139 passive radiator (SP1042), T27 tweeter (SP1032)
Crossover: SP1065