Information supplied by Jim in Australia a current Full Range owner

Impedance 4 ohms nominal, (using transformer interface boxes as supplied).

Frequency response 25 Hz to 30 KHz (+ - db not stated)

Sound pressure 115db using 4 channels at 100watts (ie 2 stereo amps or 4 monos)

Cross over points 400Hz and 3500Hz

My speakers come with both passive (2 way) or active (2 or 3 way) crossovers. I first drove these old speakers with 100watt Krells then 250watt Classe's and lastly 400watt Krell mono's. The 100watts did the job, 250 a little better, 400 much better. They need power a pair of FBP600s would be great.