wrms vs din

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lenjack
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wrms vs din

Post by lenjack » 15 Jun 2019 02:30

With regard to wow and flutter, I need a refresher on wrms vs din measurements. I know wrms readings look better.

Also need an update on rumble measurements. I know the standard ones are:

NAB
ARLL
DIN A
DIN B
I know the latter three are based on various degrees of weighting, based on audibility, which each succ :-k eeding one yielding a better figure. What is the presumed approximate difference to be expected between them? For example, If NAB yields -35dB, what would the other three could be expected to yield? I know this is inexact. :-k

analogaudio
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Re: wrms vs din

Post by analogaudio » 16 Jun 2019 00:56

I don't have the specs in front of me but from memory I believe it is correct to say that the DIN WF measurement is a peak value. Peak values will usually be higher than rms values for the same measured WF. It can be argued that the ear is sensitive to peak wow values rather than average values so the peak reading is slightly more pessimistic and may reveal audible problems that a low rms value might conceal.

As you may know WRMS means weighted root-mean-square, which is two things in one. Weighting is a filter applied to the measured signal that changes the amplitude-frequency response, for example it might increase the gain in the band centered on 4Hz where hearing is more sensitive to wow and decrease the gain at all other frequencies. Weighting needs a statement of the filter type attached to it to be meaningful, without the knowledge of what the filter was the weighted value remains undefined.

RMS is a method of producing a measurement value of a changing waveform (WF is a changing waveform) that is strictly defined in the method of derivation of the value from the measurement. Simplifying things a bit RMS is one of the methods of deriving an average value for the changing measurement and this is usually lower in value than the peak value of the same measurement.

Regarding rumble comparisons between measurement systems it seems unlikely that a blanket statement of differences can be made since presumably each system uses different measuring and value calculation methods.

Rumble ceased to be a significant problem by the 1970s, it had to be eliminated because of the way the RIAA curve used for LP playback boosted the bass, and the rumble (100 times amplification at 20Hz compared to 1kHz) and the use of good manufacturing techniques and the elimination of cheap and cheerful noisy bearings delivered superior performance.

Unfortunately Wikipedia is not much help on these topics, but a persistent web-search might turn up something.

analogaudio
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Re: wrms vs din

Post by analogaudio » 17 Jun 2019 00:16

WF measurement is one of the topics in the small reference book by AUDIO PRECISION called Audio Measurement Handbook by Bruce Metzler, it seems to available as a free download at the AP website, both analogue and digital measurements are covered.

billshurv
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Re: wrms vs din

Post by billshurv » 17 Jun 2019 09:46

What do you want the figures for?

lenjack
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Re: wrms vs din

Post by lenjack » 17 Jun 2019 16:52

Nothing specific. Just curiosity about how the figures are laid out, not how the measurements are made. I know the same table can measure from -35 nab to -70 dinb. I know the spread from nab to arll is roughly 24dB, and from dina to dinb is roughly 9dB. Am I in the ballpark? What is the approximate spread from arll to dina? Just being nosy

billshurv
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Re: wrms vs din

Post by billshurv » 17 Jun 2019 17:18

Ah fairy nuff.

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