For many years KEF were the exclusive manufacturers of the LS5/1A monitor for the BBC, a high performance system that demanded meticulous production control. The Reference Series Model 5/1AC was a KEF designed, active system based on the same speaker, and it found use in many of the new independent radio stations of the day.   

 

The system was a two-way with active crossover network, internal 75W power amplifiers for each drive unit, thermal overload protection circuit and a three position bass equalization.  

 

Specification: Model 5/1AC
System type: Two-way, stand-mount
Enclosure type: Reflex
Size: 890 x 440 x 510 mm (35 x 17.3 x 20 inches)
Weight: 45kg (100 lbs)
Finish: Oiled Teak
Grille: Grey
Frequency range: 30Hz-15kHz
Crossover Frequency: 1.75kHz
Maximum sound pressure: 112dB at 2m on axis
Sensitivity: 775mV for full output
Input Impedance: 10kOhms balanced or unbalanced line bridging
System: SP1099
Drive Units: Goodmans C129/15pr, 2 x Celestion HF1400 tweeter
From approx. 1984: T52 tweeter (SP1187) offered as service upgrade