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Watts and speakers

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5 replies to this topic

#1 of 6 StanB



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  • Join Date: Jun 19 2005

Posted June 30 2005 - 01:23 PM

Is there an instrument that one can hook up to the posts of a speaker and measure the watts it's drawing?

#2 of 6 Michael R Price

Michael R Price


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  • Join Date: Jul 22 2001

Posted June 30 2005 - 02:44 PM

If you connect a voltmeter in AC mode across the speaker terminals, you can get a rough estimate of average power: voltage squared divided by the approximate impedance of the speakers. (Example, you have 4 ohm speakers and the voltage readings fluctuate around 5 V AC... 5^2 / 4 is about 6 watts.) Depending on the music, the peak power could be 2 to 100 times more.

#3 of 6 StanB



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Posted July 01 2005 - 01:42 AM

Thanks. I'll give that a try. Yes I have 4 ohm speakers.

#4 of 6 Alan M

Alan M

    Second Unit

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Posted July 01 2005 - 02:29 AM

There used to be an analog meter(passive) that would hook up in line to your mains to measure wattage.It was a two meter box meant to be used for home audio(it was a permanent piece to keep in your audio rack).I bought one in the late 70's from radio shack.I sold the meter in the early 80's.

I have been looking for said meter,for the last couple of years(rat shack no longer makes nor carries them) to no avail.

#5 of 6 ColinM



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Posted July 01 2005 - 03:43 AM

There's also an LED type out there somewhere....
You call that a knife?

#6 of 6 Justin Ward

Justin Ward

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Posted July 01 2005 - 08:06 AM

There's a meter I've used at college before that is used for measuring AC power. I believe it has one set of leads that go in series with the speaker to get the current, it also has two leads that go in parallel to get the voltage. It takes this values and multiplies them to get overall power.