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What circuit?
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Old 24th November 2002, 09:25 AM   #1
palesha is offline palesha  India
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Join Date: Nov 2001
Location: Pune India
Default What circuit?

I saw article about yamaha subwoofer. They claim to have used negative-impedance output drive amplifier circuit. The webpage to download is http://www.yamaha.co.jp/english/prod...o/ystsw005.pdf
I am intersted to know more about this. Can anybody guide?
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Old 24th November 2002, 10:18 PM   #2
P.Lacombe is offline P.Lacombe  France
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Join Date: Jul 2001
Location: Orleans, France
Adding a negative resistance in series with a driver is a well known method to better control the motion of the moving coil.

Suppose you add a -7 ohms resistance in series with a voice coil, which have a dc resistance of 8 ohms. Final result is that you get a driver with 1 ohms dc resistance, and any erratic motion of the cone (caused by resonance, or non-linearity) is 8 times more cancelled by the power amplifier (which must withstand a loading impedance as low as 1 ohm).

Don't forget that negative resistance must supply some power, that is needs to be an amplifier, in fact.

The whole system can be seen as a kind of motional feedback.

Regards, Pierre Lacombe.
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