A Test. How much Voltage (power) do your speakers need? - Page 48 - diyAudio
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View Poll Results: I measured the test tone at:
2 volts or less 144 37.21%
Between 2-5 volts 131 33.85%
Between 5-10 volts 51 13.18%
Between 10-20 volts 24 6.20%
Over 20 volts. 37 9.56%
Voters: 387. You may not vote on this poll

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Old 7th February 2012, 05:19 PM   #471
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Default using the sine...makes sense

I'd say Tom D does get it. As for the music sample, what are we to measure that with? I got 5 volts on loud sustained music, 8 volts with the tone.

X4 on the tone gets me to 128 watts at 0 db, right? So I have barely enough power.

Last edited by phivates; 7th February 2012 at 05:22 PM. Reason: headroom comment
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Old 7th February 2012, 06:32 PM   #472
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With the music sample, basically you listen to it and you can do it two ways.

The first way is set the volume control to the position you would set it to when normally listening to a piece of music like that. After having set the volume control play one of Pano's test tones, either the -12 or -18 will will do. Measure the amplifier voltage and then multiply it by the correct factor, 4x for the -12dB tone and 7.994x for the -18dB value. This will tell you the maximum amount of rms voltage swing you need to reproduce the peaks of a 0dB sine wave at what you could call your normal listening volume for a dynamic piece of music.

The second way is to do the same as above, but set the volume control to the loudest you would ever want to listen to the system at with that piece of music. Then repeat the above test. This time the result will tell you how much voltage swing you need for a dynamic piece of music played as loud as you're ever likely to play it.
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Old 7th February 2012, 06:57 PM   #473
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I don't understand what Tom is getting at with the difference software. it's not like clipping, current limitation or other things can't be seen using simpler methods, e.g. using a scope with sines.
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Old 7th February 2012, 07:21 PM   #474
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Quote:
Originally Posted by mr_push_pull View Post
I don't understand what Tom is getting at with the difference software. it's not like clipping, current limitation or other things can't be seen using simpler methods, e.g. using a scope with sines.
As he says:
"While playing music X at level X, one can see if the amplifier residual has spikes or transient like stuff in it which happens when the output doesn’t track the input (including things like distortion). The cool part is you can hear it, the not cool part is there are no measurements, just auralization of it via the output file."

There are some types of amplifier distortion (crossover distortion, for instance) that are most apparent at low voltage levels of output like many here have measured, and actually become less noticeable when level is high.

The type of test Tom suggests would give you an idea of the linearity of your amplifier, and if the non-liniearities cause objectionable sound quality, as you will only hear the "garbage".

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Old 7th February 2012, 08:08 PM   #475
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I still don't understand.
how is that type of measurement more telling than using a scope/sound board, FFT analysis etc?
and how is xover distortion in the amp related to this topic?
anyway, if you wish just go ahead with the test. chances are that that you won't find anything relevant. with decent amps distortions are way more subtle than anything that would show using the run of the mill sound card and not show in THD/IMD plots.
it may be a whole different story with a very good SC like the Lynx etc and you may find some differences that are averaged out with FFT measurements.
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Old 7th February 2012, 08:12 PM   #476
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also, with some amps like most class A, non-feedback designs, harmonic distortions are so high that you may have a hard time interpreting the difference signal. just sayin'...
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Old 7th February 2012, 08:26 PM   #477
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Audio diffmaker isn't really suitable for comparing wave forms from which to try and figure out system distortion. It isn't accurate enough for that, at least when I tried it, it wasn't. The results kept varying quite significantly from one repeat of a test to the next and this most certainly wasn't system related.

If the levels of the recorded sound, from the amplifier, were precisely matched to the recording level of the music (I think diff maker corrects for levels anyway?) then diffmaker would start showing gross differences if the peaks were consistently clipped throughout the musical work. The trouble here is I don't know how diffmaker sets levels, it might screw it up if the peaks from the amplifier are clipped. So as Tom says you would need to precisely match the levels with your resistor divider on the output of the amplifier otherwise it could create trouble. This seems an overly complicated way to check if ones amplifier is clipping with music when reproduced at a certain volume level from a digital source.
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Old 7th February 2012, 09:44 PM   #478
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Never have so many read so much into so little.

Why do people think this is a test of amplifier or loudspeaker quality, distortion, power supplies, dynamics, compression? It isn't any of those things, no not at all.
It's just a simple test that can be done accurately with simple tools to tell you what peak voltages you can expect.

Once you've measured, you can calculate whether or not you amp is close to clipping - that's all. Nothing more. All those other parameters are nice to know, but this test will NOT tell you that.

This was meant as a simple test to tell you what voltages to expect at your speakers. It's turned into an exorcise for reading into it things that just aren't there.

On another note. It looks like the 2-5V has pulled ahead by a nose! Where will they be at the finish line?
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Old 7th February 2012, 11:43 PM   #479
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Pano, you seem disgruntled, Don't be. My little aspie brain has analyzed your test for any flaws and it is, for lack of a better term, perfect. (5th should enjoy that)

There will always be problems explaining how to do something. People tend to inject their own bias into instructions. That is not your fault, it's just humans communicating in our own inefficient ways.

Tom seems to want to help by adding more variables and conclusions to cover bases that are applicable to his reality. Maybe he should start 'Tom's helpful testing suggestions' thread. I'd read it.

enjoy the day,
revb.
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Old 8th February 2012, 12:00 AM   #480
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Quote:
Originally Posted by phivates View Post
As for the music sample, what are we to measure that with?
Your ears? The idea is to play it at what you feel is a realistic level on your system. I don't know where you would realistically set the SPL on this piece. Maybe 100-105dB peak, as would be heard in the good seats?
Quote:
I got 5 volts on loud sustained music, 8 volts with the tone.
With the -12dB tone after setting your level?
Quote:
X4 on the tone gets me to 128 watts at 0 db, right?
From the -12dB tone, yes. That's peak, not RMS. An amp that can do 60WPC clean on a sine wave could hit your peaks. You might want a little more headroom if you play that loud often.
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