# measuring difference in amp output



## mjongkamp (Feb 27, 2009)

Is there an other way, besides measuring Decibel, to measure the difference in left/right speaker output of an amp? And how exactly? (with a multimeter?)

This is why: I bought an Roksan Kandy last year but I heard a difference in output specialy noticable with lower volume settings. Right is louder than Left speaker so the stereo image is leaning to the right. I went back to the dealer and tested my amp there again. There it was not reproduceable. (then back home I thought it was because we played it harder).

So now this weekend I experimented with REW and did some first measurements. Right was 6.3 downto 1.3 decibels louder when cranked from say 7 to 12 o clock on the volumepot. (i never use it louder than 8 o clock because I have a smalle room). Thats a huge difference! each 3 decibels is twice as hard.

But I am not satisfied/confident with the accuracy of the measurement I did with a full range mic.

So i was thinking. is there a way to measure current or something at speaker output connectors with a multimeter to see the difference?


I hope you can help me.:help:

Michael


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## brucek (Apr 11, 2006)

> Is there an other way, besides measuring Decibel, to measure the difference in left/right speaker output of an amp?


Sure, just measure the speaker terminals with a digital multimeter set to AC volts.

Run REW and select the signal generator and play a tone into your receiver using a Y-splitter to the left and right channel of the AUX or CD input. This way you know both channels of the amp should be receiving the same input signal level. Don't leave the tone on too long if you're playing it loud - you don't want to harm your speakers.

When you measure the AC volts at the amps output, the voltage level should be relatively close.

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

An asymmetrical room and/or system set-up could account for this to a certain etent by way of pure acoustics (assuming everything in the electronics is in order). 

For instance, if one speaker is near a corner and the other near an open doorway, the former will have greater bass output.

Likewise, if one speaker is adjacent to something highly absorptive, like a heavy curtain, that would tend to "soak up" the high and upper mid frequencies that would otherwise reflect to the listening position. This would tend to bias the image to the other speaker.

Regards,
Wayne


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## mjongkamp (Feb 27, 2009)

brucek said:


> Sure, just measure the speaker terminals with a digital multimeter set to AC volts.
> brucek


Hi, I did a fast first measurement and noticed that I didn't get a lot of AC Volts. This weekend I will do this more accurate. I measured 1V when playing at +/- 25%. My multimeter was set to V~ 200V (lowest). Do I have to get an other one with finer measurement capabilities? Or did I something else wrong? I simply measured over + and - of the speaker wire when connected/disconnected (same results). I found a formula on the internet (V^V)/Resistance of speaker = Watt. So when I do this (1^1)3.6 ohm = 0.27W. That's a bit low for a 2x220W amp and I don't think this is correct because it was pretty loud in my ears.

So I will try it again this weekend. Thanks for the reply!:T



Wayne A. Pflughaupt said:


> An asymmetrical room and/or system set-up could account for this to a certain etent by way of pure acoustics (assuming everything in the electronics is in order).


Hi, You have a point! I think that's indeed partialy the case here which increase my perception of the balance shift. My right speaker is a bit in a corner while the left isn't. But when measuring I put the speakers side by side away from the corners and I can hear and measure a difference in output. Even my right speaker opens up sooner than the left when turning volume from 0 to ... . When I switch the speaker cables then it's the other way arround. Left opens up sooner en sounds louder then the right speaker.

Thanks for the reply. :T


michael


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## lcaillo (May 2, 2006)

What are you playing while measuring? To get meaningful power measurements you need to use a meter with true RMS capability, use a sine wave test tone, and know the impedance of your speaker at that frequency. For relative measurements, you can use any meter and a test tone, but don't try to make sense of the numbers...


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## mjongkamp (Feb 27, 2009)

lcaillo said:


> What are you playing while measuring? To get meaningful power measurements you need to use a meter with true RMS capability, use a sine wave test tone, and know the impedance of your speaker at that frequency. For relative measurements, you can use any meter and a test tone, but don't try to make sense of the numbers...


Hmm, Ok! I don't have a RMS capable meter... I played a 500Hz -10db test tone of a test cd. I will look at that a bit closer maybe another track will do the trick :scratch:

What do you mean with a sine wave test tone. Do you mean a sine sweep tone? (aren't all sounds waves?). 

To be continued:scratchhead:


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## lcaillo (May 2, 2006)

If your meter is not RMS and is measuring peak voltage, 1 v peak is about .7 v RMS. I do not understand the meaning of +/-25%. If you mean about 1/4 of the way up on your volume control, then it would only be a little power and your reading is not that far out of what might be expected.


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## brucek (Apr 11, 2006)

> My multimeter was set to V~ 200V (lowest). Do I have to get an other one with finer measurement capabilities?


I've never seen a meter with the lowest scale of 200V. Get a meter that has some decent scaling. They're dirt cheap at the hardware store.



> I found a formula on the internet


You don't need to be concerned about the actual power or formulas or RMS or anything other than whether the right and left produce the same voltage when a constant tone (sine wave) is played.

brucek


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## Mike P. (Apr 6, 2007)

If the right is louder then the left, switch the speakers. If the left becomes louder then you have a speaker issue. If not, the speakers have been eliminated from being the problem.


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