# How to measure actual speaker output wattage from a receiver?

Discussion in 'Archived Threads 2001-2004' started by BenG, Apr 20, 2002.

1. ### BenG Agent

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Can this be done using a simple multimeter (with banana-plug leads)?

2. ### keir Stunt Coordinator

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im also interested in the answer to this question. im an electrical engineering student but only a freshman :b

3. ### Kevin. W Screenwriter

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Would also like to know.:b

Kevin

4. ### Arthur S Cinematographer

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I am not an EE so take this lightly. In reading years and years of receiver tests, my understanding is that real world output is measured using very large resistors in banks for muti-channel testing.

Somehow, I'm guessing that if you could get valid measurements just using a simple mutimeter, the magazine testers would not complain that some high power amps were a challenge to their complement of resistors.

Artie

5. ### Fredrik E Stunt Coordinator

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It can be done with a simple multimeter set to measure AC voltage, and with the amplifier connected to a known resistive load, IF the signal coming out of the amp is a pure sine wave.

A speaker is a more complex load than a resistor, and if you are gonna measure the output with a speaker as the load, and if you're doing the measurements on anything other than pure sine waves, then you need more advanced instruments than a cheap multimeter.

But, if you want to do a simple measurement, just connect your amp to a sine wave signal source with a known frequency (preferably 1kHz), connect the output to a high-wattage resistor of a known value, for example 8 ohms, then measure the output with a multimeter set to measure volts AC.

The output power will be P=(U*U)/R where P is the output power in watts, U is the AC voltage in volts, and R is the resistor's value in ohms.

Also, cheap multimeters will only show the correct voltage for low frequencies, for example, they may be limited to a frequency range of 20-5000 Hz.

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