Designed to be positioned vertically on a speaker stand, Model 104aB is
a further development of the highly acclaimed Model 104, 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.
The new network was designed by computer and in combination with the t27 it gives a close
approach to a theoretical third order Butterworth response. A comparasion of
measured and theoretical responses shows that sound output remains within ±1 dB
of the ideal curve over most of the frequency range from 500 to 20,000 Hz.
Likewise the phase response is very nearly perfect. KEF engineers have called
the new circuit an acoustic Butterworth (aB) filter network.
The aB section has three functions:
1 - To compensate for the high frequency roll-off
due to voice coil inductance.
2 - To exactly
compensate for the Q and impedance of the drive unit at this fundamental
response frequency.
3 - To provide
terminal volts on the drive unit for a constant voltage input, which vary
with frequency in such a way that the acoustical frequency response
corresponds to that of a third order Butterworth high pass filter.
The effect of the modification is immediately audible as a marked
reduction in colouration and is particularly beneficial in the reproduction of
voices and stringed instruments.
The improvement in transient response gives increased depth perspective
and much sharper imaging when reproducing stereophonic signals.
To achieve an extended frequency response from a compact cabinet
without loss of efficiency. Model 104aB incorporates a 13" x 9" bass
radiator acoustically coupled to an 8" bass unit. Operating in phase below
45 Hz the two units combine to offer the equivalent radiating area of a
15" bass unit. All this from an enclosure just 13' wide. This system is
rated to handle 100 watts on normal musical programme and the high frequency
unit is protected by a fuse against fault conditions such as switching
transients and high speed spooling.
Model 104 loudspeaker systems may be upgrated to Model 104aB
specification using the Model 104 modification kit which is available from KEF dealers.
Specifications:
System: 2-way, stand-mount with
passive radiator
Drive Units:
Low Frequency : 1 x B200 bass
unit (Sp1039); 1 x BD139 passive radiator (SP1042)
Highh Frequency : T27 tweeter
(SP1032)
Crossover : SP1065
Rated Max. Power: 100 watts
programme
Frequency Response: 50 - 20,000
Hz ±2 dB
Nominal Impedance: 8 Ω
System Resonance: 35 Hz
mechanical reflex
Dividing Frequencies: 45 Hz and
3,000 Hz
Sensitivity: 12,5 watts for 96
dB (at 1 m and 400 Hz in anechoic conditions)
Amplifier Requirements: 15- 100
watts into 8 Ω
Internal Volume: 35,5 litres
Finishes: Walnut or Teak
Grille: Black foam
Dimensions (H x W x D): 630 x
330 x 260 mm (24,8" x 13" x 10,2")
