Multimeter to test power output at speaker terminals?

[markthefixer]

The difference in voltages between the channels MAY look large, sometimes I have encountered what to my picky mind would be too much, until I calculate a dB ratio for the two (easy for the types of meters I use) and find they are only a dB off from each other. THREE dB though is a huge voltage difference.

I would NOT expect close voltage tracking (numerically) on aged, vintage equipment.

 

[BrocLuno]

Funny, I live on the left coast and I have have a somewhat higher signal on the left channel in three different receivers (all different MFGs)?

I think most rock and folk music gets the bass assigned to the left channel in engineering? That signal pushes the left channel current requirement up, so the voltage tracks and apparent power does too?

 

[Raphael]

Funny, I live on the left coast and I have have a somewhat higher signal on the left channel in three different receivers (all different MFGs)?

I think most rock and folk music gets the bass assigned to the left channel in engineering? That signal pushes the left channel current requirement up, so the voltage tracks and apparent power does too?

Hmmmm . . . Interesting observation/question. I wonder who will have an answer for us?

 

[rushfan]

I would NOT expect close voltage tracking (numerically) on aged, vintage equipment.

I was hoping that the relatively low DC offset numbers that I was able to achieve with the SX-880 were an indicator of general excellent health of the unit. Both channels got down to and have stayed around 0 mV - 1.8 mV.

Funny thing - I was jamming to the stereo today (loud enough to hear over my drum kit ) and the right channel seemed louder.

 

[justw]

not if you're looking for POWER OUT. You must meas. at the spkr terminals.
Yes the pin/tip is the signal.

JustW, how do you generate a tone from a PC. Don't you need special software?

I use CoolEdit. I would guess that there are some freeware or shareware apps out there to do this. Though, I can't seem to find any with a quick look at Google.

 

[justw]

Is a "True RMS" multimeter better for measuring power? Standard meters won't accurately measure 1khz AC, they are only rated at 60hz, no?

Yep, a True RMS would be preferable if using a digital meter. In an analog meter it's RMS. The True RMS features allow for an "RMS" like measurement of non-sinusoidal waveforms. Freq reponse of the meter would be manufacturer dependent. I would expect 1kHz to be fine for relative measurements.

 

[Scuzzer]

I use CoolEdit. I would guess that there are some freeware or shareware apps out there to do this. Though, I can't seem to find any with a quick look at Google.

I downloaded a decent little program called SineGen. You should be able to google it.

 

[justw]

I up'd a zip file of a test tone to the DIY forum.

here: www.audiokarma.org/forums/showthread.php?t=127442

 

[JohnInICT]

Sorry to bring up an old thread..but has anyone tried this? What setting on the AC voltmeter do you use...if you are testing through the speakers terminals..what are the resistors for?

Play a test tone, 1 kHz is standard, into an 8Ω load, or speakers. If you use speakers don't play so loudly that it damages your speakers. Set your voltmeter for AC Volts. Measure the volts across the speaker terminals. Power is: E²/R where E = volts RMS and R is resistance of load. Both channels should be the same at a given setting of the volume pot. Note: volume pots can tend to not track perfectly but small differences should be inaudible.

You can pick up a couple of 10 watt resistors at the Shack. You can generate a test tone on your computer, or have someone do it, and burn to a CD.

 

[whoaru99]

If you are trying for most accurate measurement then use matched resistors, or at least resistors for which you can measure the values. The problem with speakers is that the DC resistance you measure with the ohmmeter may not be, and likely isn't, the impedance it presents to the amplifier at any given frequency.

Most multimeters these days will autorange to the correct value, but if not then the voltage you'll be looking for will be relative to how much output you expect of the amp.

E = Square Root of (P x R)

E = Voltage
P = Watts
R = Resistance

So, if you were expecting 10W of output at 8 ohms you'd expect to see roughly 8.9 volts.

 

[JohnInICT]

How would I set it up with resistors? Individual speaker wires with 8 ohm resistors on the end of each..plug one into the + and one into the - and test individually..I'm confused...lol

What setting on my voltmeter and I'm assuming the resistance in the equation would be 8..correct?

 

[studio1]

Testing the actual power produced by an amplifier is somewhat meaningless and doesn't reflect 'true life conditions' which as mentioned before are influenced by speaker impedance (which is not the same as DC resistance), cable length and so on.

If you want to measure the outputs of your sources - tuner, cassette deck etc you need to get a 1 kHz tone at 0VU being produced by the unit, and measure the output with an AC millivoltmeter.
The standard output level is -10 dBV which is ~ 0.31 volts (RMS).

In terms of the two meters not tracking accurately, this is more likely to be due to the meter drive circuitry being out of tolerance or not aligned correctly. Some meter drivers have presets to calibrate them. You'd need to feed a 1 kHz tone into the unit at -10 dBV to calibrate them accurately at 0VU.

 

[EchoWars]

The previous poster who said that most handheld meters won't give a proper reading at 1KHz is correct. You need to look at the specifications of the meter to see what they give as its AC frequency response. If it is not given at all, you can safely assume that it rolls off pretty quickly after 120Hz.

 

[JohnInICT]

I downloaded a tone gen. to my android phone with the intention of feeding it into the aux on the receiver. I will check the multimeters I have to find out the AC response. If it won't 1KHz, can I test on a different freq?

How do I use the resistors to test as mentioned before as opposed to using the speaker terminals?

 

[EchoWars]

Most cheap meters do OK at 120Hz or 240Hz. Above that is a grey area.

The resistor is simply connected in place of a speaker. It must be rated for whatever wattage you plan to push into it.

 

[xratedpez]

Glenn et al., is it true that an analog MM has a much wider frequency response?

My Simpson 260-3 is rated from 6Hz to 500kHz, and gives ratings in terms of RMS using germanium diodes in a bridge circuit. As a result, are these old meters superior for testing extremely high frequency AC measurements, or less accurate due to lack of IC's?