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Old Yesterday, 7:05 pm   #1641
GrimJosef
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Default Re: The Audiophoolery Thread.

With serious engineering effort professional speaker makers have done a fair bit better than 2%. My Yamaha NS1000s, which show what a really big corporation is capable of when it is prepared to throw enormous amounts of money at a problem, got second and third harmonics down into the 0.1% regime above 500Hz and were still only 0.3% at 100Hz (measurements taken at 90dB at 1m). The intermodulation distortion wasn't significantly higher. Not bad for 1970's technology ! Among other things the production of the beryllium domes for the mid-range driver and the tweeter made the speakers uneconomic though, and Yamaha eventually threw in the towel on them for business reasons.

Cheers,

GJ
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Old Yesterday, 7:59 pm   #1642
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Default Re: The Audiophoolery Thread.

I like Craig's suggested esoteric woods, and I really think meteorite iron is under-used in high-end audio.

We could confabulate and concoct some truly special cables., speaker magnets and whatnot. Where we would fail is in concocting the reassuring language needed to go along with them. Either our consciences would kick in, or we'd just die of laughing. It's a bit like that Monty Python sketch about that joke which was fatally funny.

I got as far as typing 'Acoustic textures' and then I needed a wee rest in a quiet room.

David
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Old Yesterday, 10:58 pm   #1643
Craig Sawyers
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Default Re: The Audiophoolery Thread.

Quote:
Originally Posted by GrimJosef View Post
With serious engineering effort professional speaker makers have done a fair bit better than 2%. My Yamaha NS1000s, which show what a really big corporation is capable of when it is prepared to throw enormous amounts of money at a problem, got second and third harmonics down into the 0.1% regime above 500Hz and were still only 0.3% at 100Hz (measurements taken at 90dB at 1m). The intermodulation distortion wasn't significantly higher. Not bad for 1970's technology ! Among other things the production of the beryllium domes for the mid-range driver and the tweeter made the speakers uneconomic though, and Yamaha eventually threw in the towel on them for business reasons.

Cheers,

GJ
Sine wave harmonic distortion at 90dB (so around 1W input power at a single frequency) is a very small window into a loudspeaker's overall performance.

As soon as you use multiple tones you get doppler distortion, and with typical music delayed compression as a result of the voice coil heating up.

With healthy levels of music, at sustained higher levels the voice coil of a driver can get way above 100C. At 0.4%/C the voice coil can be 40% higher resistance, and get 3dB quieter.

That is before you start on the more esoteric distortion mechanisms which play a role in all moving coil loudspeaker drivers:

https://www.klippel.de/know-how/literature/papers.html

The thermal compression paper alone is enough to give a headache

https://www.klippel.de/fileadmin/kli...ransfer_03.pdf

Klippel's software suite is what most driver manufacturers use to optimize the performance of their units

Craig
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Old Yesterday, 11:10 pm   #1644
Craig Sawyers
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Default Re: The Audiophoolery Thread.

There is also an excellent series of pages with chapter and verse on distortion mechanisms in loudspeaker drivers by Siegfried Linkwitz (RIP) here https://www.linkwitzlab.com/frontiers.htm

Craig
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Old Today, 8:21 am   #1645
stevehertz
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Default Re: The Audiophoolery Thread.

Good info Craig, thanks.
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Old Today, 9:18 am   #1646
Craig Sawyers
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Default Re: The Audiophoolery Thread.

This is an interesting test on Klippel's site for audibility of distortion using real music. It is a randomised trial, and comes up with an audibility threshold.

http://www.klippel.de/listeningtest/

I did the test with a short section of Tracy Chapman (which I know) and just used the tiny and somewhat ancient Boston speakers driven from my PC with unknown distortion in themselves. My threshold in these pretty uncontrolled conditions was -36dB, or 1.5%. That apparently, of 14,000 submitted tests 13dB below the mean.

There were some whose threshold was -54dB or 0.2%. I must try it out on my main system and see what I get.

Basically it shows that audibility of harmonic distortion is not low. So sub ppm distortion in modern op amps like the LM4562 is many orders of magnitude below audibility.

Craig
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