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Those speakers were known as dynamic speakers, they used the big coil on the back as apower suupply filter choke and to create the magnetic field for the voice coil.
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Hi techcon.
You are correct. "Give that man a kewpie doll!"
Because it was not practical to achieve the necessary constant-level magnetic field strength using available permanent magnets back in the old days, they drove a DC signal through a speaker's "field coil." And that's the way they created their desired constant-level magnetic field.
By the way; I'm referring to those old floor-model radios in their truly gorgeous wooden cabinets.
techcon, I have another question for you. What problem was caused in those radios that DID use a speaker's field coil as an inductor to attenuate AC ripple in some DC power supply?
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Only thing I can think of right off is some hum in the audio.
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Hi techcon.
Again, you are correct. I see my questions are two easy for you.