The KEF Model 104aB, launched in 1976 by the British brand KEF, was an evolution of the pioneering Model 104 (1973). The "aB" stands for "Acoustic Butterworth," representing an optimized crossover filter design that ensured smooth, accurate acoustic roll-off between its drivers.
 
Design and Evolution
The Origin (1973): KEF introduced the original Model 104 as an early entry in its digital-aided Reference Series, utilizing an 8-inch B200 bass/midrange driver and a T27 tweeter.
The "aB" Update (1976): KEF upgraded the crossover network to an Acoustic Butterworth response, markedly reducing midrange and treble coloration.
Upgrade Path: KEF even offered official 104-to-104aB modification kits via dealers so older speaker owners could get the revised acoustic performance.
 
Key Technical Specifications
Driver Layout: Two-way system featuring a T27 high-frequency tweeter, a B200 (8-inch) bextrene-cone bass/midrange driver, and a coupled BD139 passive bass radiator (or auxiliary bass radiator configuration) to extend low-end response.
Enclosure: Sealed/passive-radiator integrated 35.5-liter cabinet designed to give deep bass from a relatively slim bookshelf/standmount footprint.
Acoustic Contour Control: Featured a three-position switch on the front baffle providing ± 2 dB of adjustment to the midrange level for room tuning.
 
If required, we provide in-house produced wooden floor stands, which tilt these large floorstanders to an optimal listening positioning.