Sound Quality Vs. Measurements

[FrankWW]

JCX, that Doppler topic should be quarantined, just like a cable threads, pleeeze, not here.

[Wavebourn]

Originally Posted by FrankWW

JCX, that Doppler topic should be quarantined, just like a cable threads, pleeeze, not here.

I proposed long time ago to move it here to the Lounge.

[ThorstenL]

Hi,

Originally Posted by wahab

You did surely read that i mentionned "measurements", yet you re implying that i m talking of THD only..

I am not implying that THD is the only one that matters or that you where talking only about THD, but I selected THD as one particular measurement to illustrate the fallacy of:

"There s indeed total correlation between measurements and sound quality."

In fact, the correlation between the kind of measurements currently routinely advanced as measures of quality or not for audio equipment not lack "total" correlation, they in fact lack ANY correlation with sound quality.

I could have tried the surrealist approach instead and have asked you to demonstrate how the length, width and height of the Amplifier offer "total correlation" with sound quality, as these too are measurements...

Instead I decided to be realist.

If for example I presented an Amplifier design with a THD of 3% at rated Power (H2 dominant, H3 over 12dB down on H2 and H4 another 12dB down, the rest in the noisefloor), a damping factor of 8, a -3dB Bandwidth of 10Hz - 40KHz (also power bandwidth) and a SNR of 80dB (@ 1W) and stated that the amplifier needed to be used with speakers that produce > 110dB/1m at the amplifiers rated power and show flat frequency response with the stated damping factor; there would be no end of contributors here who would chastigate such a design as having poor measured performance.

Yet non would produce any evidence that given the performance I outlined there would be any audible degradation of the music listening experience, nor would it be possible to do so, for the selected/recommended Amplifier/Speaker combination.

Originally Posted by wahab

There s no point in 1ppm THD but neither in speakers with 10% THD.

I do not understand what you are saying.

I threw the 10% number in the ring as each and every speaker I can think of will have this or higher levels of HD in the 20Hz - 20KHz bandwidth when driven at rated power and/or 108db/3m...

As for one PPM THD, I routinely read here ejaculations about the latests slightly tweaked generic circuit simulating at having a few PPB (Parts Per Billion) THD...

Originally Posted by wahab

I would add that given the available technology , amps/preamps with 0.1% THD are irrelevant if the audiophile status is to be claimed...

I would suggest that your number is both too low and too high. It is trivial to demonstrate that much higher THD than 0.1% is inaudible (even with pure tones) yet it is equally trivial to demonstrate that much lower THD than 0.1% is audible (and in fact highly objectionable).

The point is, THD is meaningless. It has no use in illustrating distortion audibility.

It correlates with no external factor that determines distortion audibility, it only correlates with itself and other similar distortion measurements (e.g. IMD).

It has been outdated for at least six decades.

Ciao T

[ThorstenL]

Hi,

Originally Posted by SoNic_real_one

The speakers don't produce any IMD.

Speakers produce IMD. Any non-linear system that produces harmonic distortion MUST produce correlated IMD. Speakers also produce PIM and even signal correlated Jitter...

In fact Mr. Klippel (famous for his speaker driver analyser) has a nice poster, which illustrates the various causes of HD and IMD in speaker drivers.

http://www.klippel.de/fileadmin/klip...ity_Poster.pdf

As for quantification, Soundstage often posts HD measurements that are not very detailed, Voice Coil, Klang + Ton and Hobby HiFi routinely provide distortion measurements for all drivers they test (and the test many) and rest assured, most of these measurements do NOT look good...

iao Y

[ThorstenL]

Hi,

Originally Posted by jcx

others here are doublethinking themselves into knots over is that even a hypothetical "perfectly linear" piston driver does produce IMD from "Doppler effect"

The notion was popularised (if not invented) by PWK...

One might also note that especially with 1950's grade speaker drivers and instrumentation the measurements would appear to support such a conclusion, if the speaker cone is made to have large excursion modulation effects on high frequencies are observed.

Here again we see that the empirical evidence stands the test of time, namely that large cone excursions create high levels of IMD, even if the theories formulated to explain the observed effect are now discredited.

Hurray for empicisim, scientific theories, oh pshaw...

Ciao T

[dvv]

Originally Posted by ThorstenL

Dejan,
You are doing exactly what you claim to hate if others do it. You make absolute pronouncements, rather than stating personal preferences...

...

Don't be silly, Thorsten. I do not make absolute statements, I was very clear that to ME, that's how they sounded. Of course, their owners were deligthed with them, and that's just fine with me, it's only that I would not buy such stuff myself.

I should also add that in general, I don't much like the sound of zero overall feedback devices no matter what they are made with, because TO ME, they sound like unifinished products, as if something has been left out, sometimes unnaturally soft and rounded off, a bit like being out of absolute focus.

Again, their owners love them, and again, that's just fine with me, but not in my home.

I never did, and I never will try to convert such people to my way of thinking - some people love the priest, others prefer the priest's wife. To each his own.

[tvrgeek]

Originally Posted by FrankWW

Ultimately, the speaker can be seen as a mechanical device that produces low order harmonic distortion (2nds a nd 3rds mostly). We are used to it just the way we're used to full spectrum illumination - it doesn't change - we don't "see" it. Electronic devices are capable of producing lots of higher order harmonic distortion some of which (eg 7ths) our bodies just can't stand and we can feel it in very small concentrations just the way we can know somebody ran down a skunk even a couple miles away.

Tweeters, metal ones in particular, are fully capable of producing 5ths and 7ths, IM and other nasty things.

[dvv]

Originally Posted by tvrgeek

Tweeters, metal ones in particular, are fully capable of producing 5ths and 7ths, IM and other nasty things.

Why single out tweeters?

ANY transducer WILL produce distortion, the question is only how much of it and where.

Anyone know of a distortionless microphone, cartridge, loudspeaker, headphone ...?

Or any other audio device, for that matter?

[bcarso]

Originally Posted by dvv

Why single out tweeters?

ANY transducer WILL produce distortion, the question is only how much of it and where.

Anyone know of a distortionless microphone, cartridge, loudspeaker, headphone ...?

Or any other audio device, for that matter?

Including our ears, as for example anyone playing some of the Telemann recorder duets can discover (it's been suspected that Georg Phillip selected pitches sometime to intentionally produce a difference-frequency bass line).

Now there would be a signal processor --- a psychoacoustically Klippel-esque mirror filter/processor, to null the anticipated difference-frequency production



Brad

[FrankWW]

Originally Posted by tvrgeek

Tweeters, metal ones in particular, are fully capable of producing 5ths and 7ths, IM and other nasty things.

Sure but their 5ths and 7ths wind up some place i can't probably hear anyway. They sure can sometimes sound nasty, no doubt.

Gotta admit i was thinking of harmonics of low frequencies. If they come from upstream in the electronics, then you've got problems because of the energy component - more than 50% of energy in music is below 1000 Hz - because they show up in 700 Hz - 6kHz range. And we're really sensitive to sound from @2kHz to @ 5 -7 kHz.....

That's why I think you can hear surprisingly low amounts of distortion in an amplifier from a speaker that doesn't seem, by comparison to the amp, to have very good distortion figures.