How do I measure watts coming out of amp?

[KRiTiKaL]

I would like to create a display that tells me how many watts are being pushed out at any given volume. Also, an in room ambient/live decibel meter. Is there a web site or kit i can go to or get? Thanks in advance!

[pelly3s]

well the decibel level you can just measure with a dB meter. then with a multimeter you can measure the voltage from the speaker output, and multiply it by the amperes so it's Volt X Amp = Watt

[karl k]

I would like to create a display that tells me how many watts are being pushed out at any given volume. Also, an in room ambient/live decibel meter. Is there a web site or kit i can go to or get? Thanks in advance!How does one measure the power "on the fly"? In all my searchs for such a thing, I've only found 2 items that measure in watts. All others are in DB's.

http://store.qkits.com/serv/qkits/velleman/pages/K4307.asp

http://www.silverflight.com/au/processors/dbdisplays.htm

The Furman VU-40 is the only manufactured box I've seen.

The Velleman kit is what I use on my subs and believe it to be accurate but lacking in resolution. For $30us, good investment and looks cool too!

[skeptic]

You can't!

All of the devices mentioned regardless of what someone thinks their ads say or what the meters themselves say are voltmeters and nothing more. They may be calibrated to read how much power WOULD be delivered to an assumed resistive load of one value or another but when the amplifier is connected to a loudspeaker that assumption is always going to be wrong.

Wattage delivered to a load by audio amplifiers at this stage of the state of the art can only be measured on a laboratory test bench by an electronics technician, not by an inexpensive display to amuse you. If such a display were to exist, it would have to contain a small fast computer which would take the measured output voltage and output current, AND it would have to continuously compare the two waveforms and determine the phase angle between them. Then for a given period, it would average them, and multiply the voltage by the current and multiply that product by the cosine of the phase angle and display the result. This can not be predicted by a simple meter because not only is it different from one speaker to the next but it is different for the same speaker depending on what frequency or frequencies and power level it is operating at. Today such a display would have to be custom built and therefore probably cost many thousands of dollars. In the future if there is a demand for it and it were to be mass producted, the price could one day be affordable to the average audiophile, but not today.

[IsmaVA]

How does one measure the power "on the fly"? In all my searchs for such a thing, I've only found 2 items that measure in watts. All others are in DB's.

http://store.qkits.com/serv/qkits/velleman/pages/K4307.asp

http://www.silverflight.com/au/processors/dbdisplays.htm

The Furman VU-40 is the only manufactured box I've seen.

The Velleman kit is what I use on my subs and believe it to be accurate but lacking in resolution. For $30us, good investment and looks cool too!

What do you mean by "accurate, but lacking in resolution"?

[karl k]

What do you mean by "accurate, but lacking in resolution"?
doesn't have a very fine amount of resolution since the bargraph is still based on 10 led's for the full scale but when the 100wt light comes on, you are pretty close to 100wts output... when the 20wt light comes on, your pretty close to 20wts output. I have comfirmed this with a db meter comparing actual acoustical output with the power meter reading of electrical output and what the acoustical output should be at that power level.

[IsmaVA]

ok . . .

[KRiTiKaL]

Hey thx, as long as its accurate within 10watts its ok.