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Misleading Measurements


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I would like to propose a different position on the relevance of measurements, from a sound and vibration engineering, rather than EE perspective.

 

The last items in the audio chain before your ears are either the loudspeaker or headphone drivers. The measurement that I am then most interested in is the displacement and phase of the driver surface, as this is what is radiating sound. I can measure this very precisely using a laser vibrometer, at single points, or map over the entire surface of the driver.

 

The proposal then is if I have a reasonably accurate system and keep it constant, I can change out components such as DACs which differentiate themselves via “superior” EE measurement parameters, and see if there is any measurable difference in terms of driver displacements. The premise then is if you have not changed the driver displacement, you have not introduced a significant audible change with the introduction of the superior EE measuring component in the system.

 

I realize that this would be a new way of looking at the problem, and not everyone has access to laser vibrometer measurement facilities, but at least this would be a type of measurement parameter that would be guaranteed to have an effect on audibility. Maybe someone with the right connections to a lab could have a system set up there where 5 different DACs, having low to high SINAD numbers, could be tested as a feasibility study?

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11 minutes ago, PeterSt said:

 

It wouldn't be really different from the way I record and represent changes (I still see nobody doing that), although that way would be more indirect than "viewing" the speaker driver's surface.

 

 

You started out so nicely, and I was ready to invite you over, but you end up saying that you do not own (or can possess) said equipment ?

 

About everything which I change in the XXHighEnd software alone, is totally easily "feelable" at the woofers. It goes from nice sines (when intended to) to super square mess (sines still intended). So ... come over with that stuff ...

please. 🤪 

You are in the Netherlands, correct?

 

I think then that you should be able to find a few good acoustics labs nearby...

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1 minute ago, Audiophile Neuroscience said:

Nice. At least we are moving downstream, from the output of the DAC (comparing signals with signals) to the output of the sound wave transducer.

One day we should be able to use a vibrometer at the tympanic membrane level, even further downstream. One day it may be even possible to tune into the cochlear transduced signal. Oh wait, that's what the brain is for ...😁🤣

 

Just kidding, sounds like a very cool idea. The caveat would be the same as other measurements - how valid is the result (is it sensitive, is it reliable etc)

 

 

This concept just has to be tested out in a small feasibility study first. Some colleagues have used laser vibrometers to measure nano scale vibrations in materials, does that sound sensitive enough? I'll check with them sometime to see if they have any suggestions on how this could be done.

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3 minutes ago, The Computer Audiophile said:


We won’t get anywhere on this one. 
 

I look at it as, either measurements matter or they don’t. Picking and choosing which unhearable measurements matter, doesn’t make sense to me unless one is pushing an agenda. 

This now comes back to my earlier suggestion of finding a more meaningful sound and vibration measurement as a reference for audio component audibility. I'm not suggesting that what I proposed is the right one, but I remain frustrated that all the audio-related EE measurements still are not easily explained in terms of the generation of sound waves. 

 

You are correct, we won't get anywhere on this discussion unless the perspective changes.

 

 

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  • 3 weeks later...

This link is for a research paper that contains the parameters used to estimate IMD analytically for a Class D amp case, and is compared to a Matlab DSP simulation, and also measurements on the actual amplifier:

 

https://core.ac.uk/download/pdf/162670379.pdf

 

Can this case be used as a test case for DISTORT? This would help to stop the infinite-loop discussions about what DISTORT actually is doing...

 

Also, as far back as 2010, there were publications about a Distortion Analysis Toolkit which is Matlab based. Is DISTORT doing anything different than this available software, or Matlab DSP functions for instance?

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