The instrument
The D 520 from Dynacord was specially designed for the Imperator amplifier. Both devices came onto the market in 1970.
Details
The D 520 loudspeaker is built for a continuous load (sine wave) of 80 watts and peak values of 110 watts and has a transmission range of 40 Hz - 8000 Hz and an impedance of 16 ohms. It is equipped with a Goodmans bass speaker. (Source: Hans Ohms)