Is there a rule of thumb for powering up field coil speakers? I have a vintage cabinet with two FC speakers in it. Not sure of the brand specs etc. I'd like to get an idea of the voltage and current required to make them work. I don't plan on over a few watts powerwise to operate them. I have a few variable HV power supplies for testing if needed.Sorry if this is a dumb question.
Thanks
Thanks
I recommend the Biot-Savart toolbox in Matlab.
If you don't have access to Matlab, you can do the math in excel... I have seen Biot-Savart implementations in excel before.
You should identify the pole-piece of the speaker (material) if possible, and work to just barely saturate that material given the gap width.
You can start by measuring the resistance of the wires. I think there are ways to back out the maximum field strength of the coil from the inductance too, but I can't remember off the top of my head.
Once you have a good idea of the number of turns and the copper gauge, you can come up with a target current flow to saturate the polepiece. If the copper shielding breaks down before then (loosely drawn from coil capacitance), then you would have to go with a pulsed current instead of a DC current.
If I'm way off base, feel free to correct me. I'd love to help more on this.
If you don't have access to Matlab, you can do the math in excel... I have seen Biot-Savart implementations in excel before.
You should identify the pole-piece of the speaker (material) if possible, and work to just barely saturate that material given the gap width.
You can start by measuring the resistance of the wires. I think there are ways to back out the maximum field strength of the coil from the inductance too, but I can't remember off the top of my head.
Once you have a good idea of the number of turns and the copper gauge, you can come up with a target current flow to saturate the polepiece. If the copper shielding breaks down before then (loosely drawn from coil capacitance), then you would have to go with a pulsed current instead of a DC current.
If I'm way off base, feel free to correct me. I'd love to help more on this.
Thanks. I'm at work atm but I see a MATLAB download is available. Guess I need to do some research. I have a 6 tube (01A's) farm radio I'm trying to restore. Maybe drive a small SE amp with it to power the FC's.
I'll give it a try. Read a few things online about using a variable HV supply with an audio signal applied. Said to increase the voltage (in series with a resistor)
until the sound levels out. I guess the main issue is that many were used as the PS choke and the actual current and applications are endless.
I appreciate the help, Thanks
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