these originated in 1977 and were purposly underrated, infact every 4B made was 280 watts per side plus or minus 4 watts, during that time they came rated at 200, then 250 watts [but the output remained unchanged], in the case of the 3B I THINK it was actually 147± per side but rated at first 100, then 120, but as I never owned 3B's back then I never was that concerned and I am therefor not certain.