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Old 10th March 2006, 11:47 AM   #1
knubie is offline knubie  Norway
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Now here you have a really theoretical idea

Well you all the story about the capacitor, the inductor and the frequency, they are all over the place, all the time...
Not good friends, but they tend to meet in the middle, so to say...

If we now would make a planar or an ESL with rods, as usual by DIY, but then spin a wire around the rod, we would the have an inductor generating an electromagnetic force as used by a planar, and an electrostatic force also (I guess).
Isolation between rod and wire and power in wire...

Point is that (if used as an electrostatic) frequency response as seen by amp with inductance and capacitance is more straight as opposed to an capacitor and a resistor. If used as an planar, we wouldn't have to use all these f..... big magnets right, or am I just the ultimate dumb smuck....
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Old 11th March 2006, 02:04 PM   #2
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Point is that (if used as an electrostatic) frequency response as seen by amp with inductance and capacitance is more straight as opposed to an capacitor and a resistor. If used as an planar, we wouldn't have to use all these f..... big magnets right, or am I just the ultimate dumb smuck....
No, you’re not a “dumb smuck”. You are using your creativity to try to make something better, and that’s always admirable. But you since you admit to being a “knubie”, let me try to help a little with your understanding of inductors and capacitance, or at least convince you that you need to gain a bit more understanding elsewhere about these elements.

I can put a capacitor and a resistor together to make a low-pass filter (series R, shunt C). If I rearrange to have a series C with a shunt R, I get a high-pass filter. OK, now let’s substitute an inductor instead of the capacitor with that same resistor, and then look at these two arrangements again. The opposite effects happen: the high-pass becomes a low-pass, and the low-pass becomes a high-pass. So, this is where you are thinking of these two components as being opposites, and in a sense you’re right. In engineering, we call them “duals” rather than opposites.

The more difficult-to-understand story comes if we connect an inductor and a capacitor together. They form a resonant circuit which has a “natural” frequency at Fn=1/(2*pi*SQR(LC)). Depending on how you connect the L and the C together you could make a low-pass filter, a high-pass filter, a band-pass filter or a band-reject filter, but they all have something like either a peak or a dip at Fn. Resistors that are also in the circuit tend to dampen or blunt the sharpness of the peaking or dipping at Fn, but Fn always remains a “special” single frequency of a resonant circuit. Filter theory is well beyond what we can cover in these postings. I believe that there are several websites teaching basic electrical theory that you may want to read.

I guess my point is that, instead of inductors and capacitors neatly cancelling each other’s frequency dependent effects out, they may in fact together create a more complex, and for audio, more troublesome anomaly called resonance in the frequency response, where flat, non-resonant behavior is usually the goal. I realize in trying to write this how hard it is to explain this without trying to teach the basics, and I may have opened up a can of worms.
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Old 14th March 2006, 06:32 PM   #3
knubie is offline knubie  Norway
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thanks Brian
I know a little about filtering effects as done in crossovers but I didn't think these coil rod inductors would have big resonant frequencies in all the audio band. I'll try to calculate it one day when my ee skills have improved a bit.

Have anybody used anything like this? I mean as a eletromagnetic force kind of sound transducer like a magnetostat like Magnepan or something? They would be more handy than a big magnet if they could be made to have a broad enough range with or without resonant circuits....
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