Wattage

I know that James Watt gave his name to this measurement, Do you guys know how to measure it? I am trying to measure the max wattage of a sub woofer I have a mutimeter and I know the sub has a rating of 4 ohms, I don't want to find out by testing it (bang)

in article bnpa84$bit$ snipped-for-privacy@hercules.btinternet.com, Dave McMahon at snipped-for-privacy@btinternet.com wrote on 10/29/03 1:08 PM:
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How do you know that? I doubt that Watt had anything to do with making a watt a unit of power. He had a name that was available for appropriation.
Bill

wrote on 10/29/03 1:08 PM:
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Well, more correctly it was named after him to honor his work in early thermodynamics. You're right he didn't have anything to do with it directly.
http://level2.phys.strath.ac.uk/ScienceOnStreets/jameswatt.html
(last paragraph)
daestrom

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Watt improved the steam engine invented by Newcoming (sp?). One or the other invented the term, "horsepower." It was a natural to name the basic unit of power after Watt.

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You are better off trying to get that from the manufacturer. It is a nebulous figure anyway and lies are rampant. I assume you really want to know if your amp will smoke it. Bear in mind the numbers for amps are also more marketing than science.

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Kind of.. I must admit that the ratings they put on amps and speakers these days can be a bit erroneous depending upon where you are and where they were made!
Most (all good) amp/speaker manufacturers will give a rating in "True RMS" - probably somewhere in fine print on the back page of the manual and as far from any advertising material as they can get - and you can reliably use these ratings to configure your system. Rule-of-thumb is that the Peak RMS power of the speaker should always be higher than the per-channel Peak RMS power of the amp.
Totally ignore ratings like "PMPO" (Peak Music Power Output) - usually the absolute peak (not RMS) power of all channels of the amplifier into 2(!) ohms x the maximum possible number of speakers (note: 1 mid/high/sub = 3 speakers) you could physically connect with destroying the entire unit - but sometimes they include a large fudge factor as well to improve sales.
To put all this in perpective (FWIW), a comfortable listening level for music at 1 meter from a speaker is 1 Watt RMS. And since volume is logarithmically related to power, 10Watts is twice the volume of 1Watt...
Cameron:-)

snipped-for-privacy@spamspamgoawayrmna.com.au says...
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"Peak RMS power"? "True RMS power"?? Oh, good grief! These audiophools will buy anything!
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Also ignore *anyone* who talks about "RMS Power", peak, average, sustained, or any other qualifier.
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Good grief gert! I think we have a prime audiophool here.

says...
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1Watt...
No you bloody don't.
I'm merely trying to be helpful and learn something on the way.
Cameron:-)

snipped-for-privacy@spamspamgoawayrmna.com.au says...
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There is *NO* such thing as "RMS Power". It's an absolutely meaningless munge of terms, used to make the speaker sound knowledgeable. Anyone who professes such should be ignored immediately and permanently.
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Power is power. Though I did misspeak. Average is the only thing important from an audio amplifier.
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"1 Watt" is meaningless as it relates to loudness. You have not specified what that electrical power translates into sound pressure.

"Keith R. Williams" wrote:
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C'mon Keith, there *must* be. After all, if the manufacturer rates the equipment with that term, people will pay more for it. Of course, if you want to maximize the "true RMS power", you must connect the amp to the speakers using gold plated, argon filled, 4000psi pressurized, pre-stretched monster cables that you wash weekly with "Signal Kleen". Someone will be willing to sell you a bottle of that for 10 dollars an ounce. :-)

snipped-for-privacy@bellatlantic.net says...
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My bad! I forgot that there were unemployed "engineers" who have a need to sell shite to make the mortgage payment. Perhaps one really *does* need to maximize the "experience", even if it means enhancing the "RMS power" of the power-point presentation.

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As I said, anyone can make a mistake.
It would have been nice if, when *I* mis-spoke, you had simply corrected me without piling on a bunch of insults. You can always go back and flame someone after treating them with respect, but once you start calling someone names, you can never go back to having a professional conversation with them.

<http://www.guymacon.com/ says...
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Your clipping is interesting. You were clearly wrong in your position. I added the word "average" into my list of terms to be discarded and made the correction. "Average" is the *only* term that can be used with power (average implies time, so pick the time).
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It would have been nice if you acknowledged that you were *wrong*. Clipping posts to show your side amounts to a lie! ..at least by omission.
Please learn how to quote your opponent's position so you don't look so shallow.
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Wow! You're a big talker. However, you don't quote your opponents, but berate them. ...perhaps to make you look somehow superior? Please! Learn the rules of the Usenet and quote and respond. If you can't take heat, leave the kitchen. The Usenet isn't your mother's tea party.

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I am pretty sure that I have admitted that at least once already, but in case I didn't, here it is again; I was wrong. I mis-spoke. I read in haste, and failed to notice the reference to power rather than voltage. My mistake. I erred. It wasn't really a "position", but rather a simple error. We al make errors
It would have been nice if you had simply corrected me without piling on a bunch of insults.
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Did I mention that I was wrong? I was wrong, you know. Not only that, but I was also wrong. In other words, I was wrong. What I am getting at is that I was wrong. Do I make myself clear?
It would have been nice if you had simply corrected me without piling on a bunch of insults.

On Fri, 31 Oct 2003 22:22:53 -0500, Keith R. Williams
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Still trolling eh, Keith?

In what way does wattage differ from power? :=(
Bill

On 29 Oct 2003 21:46:39 GMT, snipped-for-privacy@aol.comGreg (Gfretwell) Gave us:
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Not if it is a reputable maker. Amp specs are true to form correct from many reliable producers of home audio equipment.

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The easiest way to do this is to read the label on the back of the speaker.
If you *really* *seriously* want to know what your sub is rated at, you would have to: 1. Hire/borrow/etc/etc. an impedance analyser from some place. 2. Hook it up in an anechoic chamber (or wear suitable hearing protection, or both ;-) 3. Chart the speaker coil impedance over the range 0Hz to 20kHz (for a sub, the impedance after about 5kHz won't tell you anything useful, but if you've got the gear you might as well measure it). 4. Take the lowest impedance value recorded and plug it into the standard formula to calculate the Max Power (RMS) at this point. 5. You now know your maximum Wattage. Congratulations!.. Depending on the quality of the speaker, the measured value should be near enough to, but slightly higher than, the value written on the label on the back of the speaker.
The only use for a multimeter in an audio environment is to check the continuity of your speaker leads. ;-)
Enjoy! Cameron:-)

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--------- You are assuming that at the lowest impedance value the speaker is resistive. However, the power with this impedance depends on the voltage- that is a measurement of impedance alone will tell you nothing about the power unless you have this other information. However, given knowledge of the impedance and the voltage or current- you then only have a figure for the power input under the conditions of the test. This is not a measure of the maximum allowable power for that speaker. Crank up the volume and the power into the speaker goes up but the impedance at a given frequency will not change or if it does- it will be at or near the point of no return. That is a sure way to test so that you know what not to do with the replacement speaker. ----------
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standard
No...ish. Given the impedance at it's lowest value and knowing the max current rating of the coil (Amps) should be enough to calculate the max power, assuming coil burnout is the most likely cause of failure (not over-extension of the core, etc. etc.). P=I^2*R last time I checked (but I haven't got a textbook nearby ;-).
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But you don't have any control of the voltage - that's completely up to the amplifier manufacturer. At some point in the impedance curve, the *amplifier* will current limit (at Max Output Power of the amp), but the speaker may be stuffed by then...
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Not the power per se - the *voltage*.
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Certainly one way to calculate max power would be to feed the speaker under test from a humungous amplifier and wind up the volume on white noise until the coil burns out. Instantaneous volts and amps at the time would give you a good indication... but I assumed the OP wanted to use the speaker afterward.
Regardless of voltage, if the current that the amp delivers exceeds the coil rating you get burnout - so the Max Power of the speaker must be related to impedance and current only (excluding coil dynamics and acoustic effects). No?
Cameron:-)