 The 5F series Twin utilized the finest heavy duty Concert Series Jensen P12-N Alnico V blue-dome loudspeakers (conservatively rated in 1957 at only 18 watts apiece).In the day, players would rarely ever open such high-fidelity amplifiers to their distortional limits.These "high-power" tweed Twin amps would deliver peaks up to 80 plus watts of power when turned high.