Question about measurements

[Joisa]

Hi,

I’m new here

I was hearing some arguments from the subjectivists, saying that testing distortion using static tones like one or multiple sine waves wouldn’t deliver same results as testing real music which has wider variation in dynamic range

So I wanted to ask why are the measurements only with sine waves and is this a valid argument ?

I’m searching for the highest transparency possible in a dac/ headphone amp combo for monitoring purposes.

Trying to avoid all the marketing bs that makes me wanna spend useless money

Also trying to avoid all audiophiles auto induced fake perception but I’m still trying to eliminate any biais this community could have too

Thanks

 

[ahofer]

I'm not sure why dynamic range would have a lot to do with it. A test tone can be presented at the same amplitude as the high end of the DR.

Usually the argument is about 'complexity' or multiple frequencies of sine wave test tones, but white/pink noise and multitone tests do exist. And, of course, in listening tests, music masks flaws much more than test tones, generally by a sizable amplitude factor (a recent jitter test I saw had about a 7-fold increase in jitter with music to be audible vs a test tone).

For the most part these objections are just red herrings intended to make consumers think that measurements don't matter.

Also, they may want to wave away a simple truth proved mathematically by Fourier: any periodic waveform can be expressed as the sum of an infinite set of sine waves. So the music is..made of simple test tones.

 

[MAB]

Hi,

I’m new here

I was hearing some arguments from the subjectivists, saying that testing distortion using static tones like one or multiple sine waves wouldn’t deliver same results as testing real music which has wider variation in dynamic range

So I wanted to ask why are the measurements only with sine waves and is this a valid argument ?

Because all waveforms can be deconstructed into individual sine waves. See Fourier Series.
You can use any waveform you like. Analyzers like Audio Precision can use any signal as a reference. Even music.

It's just that quantitative analysis of resulting distortion is difficult with music as the signal. And, music doesn't produce any new distortions that sine waves demonstrate. If using music did produce a different result it would be remarkable indeed, and have implications for many technologies outside of sound reproduction, like Radar and the JWST to name a couple... Instead of music, a signal is used at the frequency where our hearing is most sensitive. People incorrectly believe music is somehow a more difficult workload, yet ignore the fact that distortion measurements are chosen at frequencies with the highest audibility.

I’m searching for the highest transparency possible in a dac/ headphone amp combo for monitoring purposes.

RME ADI-2 FS is my goto unit for reasons in decreasing order.

1. It is reliable.
2. It has PEQ, which will make a difference.
3. It has a great headphone amp.
4. It has a DAC that is audibly transparent, although almost any DAC is audibly transparent, despite what the subjectivists say. So this is a distant fourth-place. DAC got solved 3 or 4 decades ago. Apple headphone dongles are transparent for instance.

Lots of less expensive alternatives exist, and PEQ can be applied with a PC for free.

Trying to avoid all the marketing bs that makes me wanna spend useless money

Also trying to avoid all audiophiles auto induced fake perception but I’m still trying to eliminate any biais this community could have too

Thanks

 

[RayDunzl]

Why not use "music" to "measure" distortion?

Using specific frequencies (sines) gives you a known starting point, a "pure" single frequency as a benchmark.


Then you can look to see what harmonics are generated and whether the levels are of concern or not.

Here's a speaker output in-room fed with a sine wave, where the speaker generates a strong third harmonic:

(ignore below 400hz, it's just noise in the environment)

I can conclude this speaker distorts, primarily in the third harmonic at this playback level.



On the other hand here is a single "musical" note, the electrical output of a bass guitar.

I cannot tell you if the waveform is distorted or not, becuase that's how musical tones look. The harmonics give the sound its "character" or "timbre".

Add more instruments and it will only get more complex.

 

[Joisa]

Thanks, that makes total sense

Great community

 

[kemmler3D]

why are the measurements only with sine waves

So you can see how much distortion happens at each frequency. In order to do this, you need to play only one frequency at a time and sweep it up/down.

and is this a valid argument ?

Yes and no - Amir and many other testers do IMD tests with multiple (32) tones, which is close enough to music to be a valid test, but simple enough that you can see what's going on in the FFT readout.

Amps / DACs don't have an opinion about whether they're playing music or just random noise. As long as you hit high frequencies, low frequencies, and some in between, you have covered the bases. There is this implicit attitude among "audiophiles" that music is somehow magic and changes the rules of how electricity works... but it doesn't.

wider variation in dynamic range

It's worth noting that dynamic range is the difference between the loudest / quietest thing in the signal, not how many frequencies are present.

But of course this is why amps are tested at multiple power levels.

Is it possible that some kind of dynamic nonlinear distortion is hiding in an amp, outside of the normal tests? I guess so, but the normal tests are pretty thorough.

 

[Doodski]

Thanks, that makes total sense

Great community

Additionally when torture/soak testing an amplifier if using music the amp does not get very hot but with a sine wave of 1 kHz the amp will get very hot and the amp can be tested to failure if pushed too hard with sine waves. Plus sine waves are a standardized test method that can be repeated anywhere whereas music is a varying waveform that is not a steady state due to the varying nature of music.

 

[Rja4000]

Hi,

I’m new here

I was hearing some arguments from the subjectivists, saying that testing distortion using static tones like one or multiple sine waves wouldn’t deliver same results as testing real music which has wider variation in dynamic range

So I wanted to ask why are the measurements only with sine waves and is this a valid argument ?

I’m searching for the highest transparency possible in a dac/ headphone amp combo for monitoring purposes.

Trying to avoid all the marketing bs that makes me wanna spend useless money

Also trying to avoid all audiophiles auto induced fake perception but I’m still trying to eliminate any biais this community could have too

Thanks

A few comments

1. Sine wave is a very challenging signal
One character to a signal is it's Crest factor, which is the ratio between peak voltage and the RMS voltage (which is more representative of energy).
The lower the crest factor, the more energy a signal will transport.
The lowest Crest factor is a square wave, but square waves are not easy to use for identifying distortions, especially harmonic distortions, since it actually gives an infinite number of harmonics when decomposed through FFT.
So we use a Sine wave.

2. Easy to read FFT
As said in previous posts and above, a Sine wave is just one vertical bar in an FFT. Everything else is unwanted.
So we can easily measure it.

3. Amir is actually also using a signal which looks like music in time domain but is easy tobread in FFT: that's the Multitone.

A bit like music, it is composed of multiple (32) sine waves at the same level, at various frequencies and phases.
In FFT plot, we should get 32 vertical bars, one per "tone"..

I add here one of my own Multitone measurements, because you may see in the top window how the signal looks like in time domain. As you may see, it's way more complex than a pure sine.
Amir doesn't actually translate this into figures, but a quick look at the FFT tells you if there are problems or not.
And at which frequency you would hear (or not, depending of the level) those problems.

If there were issues with music, you'd see them here, for sure.

 

[Spkrdctr]

Amps / DACs don't have an opinion about whether they're playing music or just random noise. As long as you hit high frequencies, low frequencies, and some in between, you have covered the bases. There is this implicit attitude among "audiophiles" that music is somehow magic and changes the rules of how electricity works... but it doesn't.

What? Wait, I just wasted all that money on my brand new Disney Harry Potter wand? It was a high dollar limited edition wand too. Crap, I was sucked in by those darn audiphools again!

 

[Joisa]

Thanks again for all those quality answers, I’m sure it will help more people than just me.

 

[Keith_W]

If they still don't believe in test tones, you can test with real music. Do a simple null test. If it nulls, there is no difference.