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The Need for Objective Metrics in Audio Reproduction

FrantzM

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Hi

This is something that is very dear/important to me. I came to stereo ast a very young age. 8~9 years old I was allowed/encouraged to us emy father's stereo system. I was hooked to music and its reproduction. In those times there was the notion of High Fidelity Hi-Fi... then came the High End Audio Revolution in the late 70's early 80's with the search for an Absolute Sound then the current it is all subjective mantra where whatever you like is good as long as it is expensive and "audiophile-approved" .. Bose doesn't qualify even if you were to like it, not expensive enough :D.
On the Other Hand there are the works of the AES and those of companies such as Harman and Bang & Olufsen with results to prove that there is an objective reality: That gears who measures well in some specific metrics are usually well received by a majority of listeners. Yet the High End Audio Industry and many (most?) audiophiles are not at ease with either the methodologies nor the results.
I believe that we need to encourage more in this direction . More works about what do we require from our systems and why do we like what we like. . What metrics should these be? What should an audiophile look in those measurements? What type of measurements would help? Who performs those?
Comments , discussions, etc are encouraged
 

Thomas savage

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i agree, i would like to see a more diagnostic\measurement focused process. so many times we buy products when not knowing the cause of our problem or dissatisfaction. i have three areas i need to measure to work out what a problem is but all anyone is interested in doing is selling me various expensive cures when i have no idea if they match my illness.

hi fi and hi fi dealers seem to send you strait to their drugs store to sell you their drugs but without any attempt at diagnostics. this is absurd!

my three problems i need to be diagnosed so i can fix them..
1. i get a resonance\artifact in the higher parts of a female vocal but only at certain times of the day. never early in the morning or late at night. this unpleasant sound is like a flat spot that vibrates wrong in my ear and also seems hide subtle elements in the mix. i thought this might be room acoustic related but as it never is present in early morning listening sessions this cant be true. (0400-0700) dealer not interested in this issue so buggered.

2. i have a buzz on my left speaker\ comes from the HF drivers and is constant but very low in strength. its from my left amp but i dont know what it is or how to fix it. dealer was not interested in this problem so am buggered .

3. room response, nulls and peaks. i can diagnose this but the fix given i am using a cdp (not pc based) still eludes me.

having spent so much money i cant believe i have to live with these issues, two of which i have no way of diagnosing nor do any hifi 'expert' i have come across. they just want to sell me many thousands of pounds worth of products but without knowing the cause of the problem.

can anyone help me? why does the hi fi industry just sell boxes and not address problems like these with a diagnostic lead solution.
 
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Purité Audio

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When you swap the loudspeaker cables around does the buzz change channel?
Keith
 

Thomas savage

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When you swap the loudspeaker cables around does the buzz change channel?
Keith
yes, its super low level. i have to put my ear right up to the speaker with the preamp turned off to hear it. it seems to emanate from my left mono amp. i am sure it would show up on a scope. who knows. i guess its mains related, bridge rectifier? in the amp(what ever that is lol), dont know. or maybe a u.s. transformer not coping with 50Hz.. really i am just guessing going on reading on the internet but i am sure this could be measured but no ones set up for this type of approach. tony heard it but just walked off saying he had heard worse lol WTF:rolleyes:
 

Thomas savage

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no. belles mb200, the noise is super faint but its there, not on the other side\amp. those kind of buzzes could be anything i guess. its just pain to be left with it, not knowing why.
 
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Purité Audio

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Have you spoken to the retailer, what did they say?
BW Keith
 

amirm

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Hi

This is something that is very dear/important to me. I came to stereo ast a very young age. 8~9 years old I was allowed/encouraged to us emy father's stereo system. I was hooked to music and its reproduction. In those times there was the notion of High Fidelity Hi-Fi... then came the High End Audio Revolution in the late 70's early 80's with the search for an Absolute Sound then the current it is all subjective mantra where whatever you like is good as long as it is expensive and "audiophile-approved" .. Bose doesn't qualify even if you were to like it, not expensive enough :D.
On the Other Hand there are the works of the AES and those of companies such as Harman and Bang & Olufsen with results to prove that there is an objective reality: That gears who measures well in some specific metrics are usually well received by a majority of listeners. Yet the High End Audio Industry and many (most?) audiophiles are not at ease with either the methodologies nor the results.
I believe that we need to encourage more in this direction . More works about what do we require from our systems and why do we like what we like. . What metrics should these be? What should an audiophile look in those measurements? What type of measurements would help? Who performs those?
Comments , discussions, etc are encouraged
Hi Frantz. Our current measurements are not perfect. But many of our components are so perfect that it obviates the need for better measurements.

Take THD or total harmonic distortion. It is a "dumb" number that is devoid of psychoacoustics. It treats all harmonic distortion as having equal harm. Our ear does not work that way. Higher order harmonics are more audible than low-order. That would be a problem if we were to compare two amplifiers one with THD of 1% and the other 0.5%. We could not for certain say that the latter sounds better. Outside of tube amps, our amps do far, far better. Once you are down to 0.01% versus 0.005%, it doesn't matter that THD is not psychoacoustically correct. Both values are too low for audibility.

Likewise once we measure things like jitter in DAC and find the components -90 dbFS down, it is very hard to make a case for audibility of those distortions even if we ignore the psychoacoustics effect.

So I say to the extent our electronics do exceptionally well in classical measurements, the odds of audibility difference become so small as to not be the factor to rely on.

For speakers, I only know the one story that makes sense and that is what you refer to as Harman research. Alas those measurements are expensive to perform so we are at the mercy of the manufacturer doing it.
 
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tomelex

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THD+N at .01% is part of the story. It is if you are just running a sinewave through the amp, but music is a whole lot of sinewaves all at once. Even testing on a resistor load, THD will vary with output power and frequency. And all that music going through the power amp will produce a huge, huge amount of intermodulation products, and all these can for example add up to an amp sounding like it is compressed or loss of detail, etc.

The only way to really test an audio system, is as a system, there is noise created by each components grounds, there is RF interference, there is internal mains interference, there is other stuff too, so while in isolation things might test ok, when you put them together in a system, then everything just gets worse. So, you would have to measure a system as a whole to figure out some idea of how badly it is mauling the input signals.

the belles mb amps mentioned above by Savage, there could be oscillation caused by the speaker load, they could take it in and bench test it with a resistor load and it will check out fine, but with the speaker cable and speaker load, it could cause the amp to start oscillating (if that is what it is doing...also just a weak electrolytic can cause oscillations.

To answer Frantz, just like you use a comm test set to see what happens to signals on a line, you would have to use several different tools to measure each stage along the audio path to get an idea of how a system sounds. Of course, if each component by itself is really the best it can be then you start out with better chances of getting what you want.

But, physhacoustics, that's another story. I remember that in one amp, they usually changed out a feedback cap with a different kind, and it resulted in folks preferring the sound due to the new cap. Measurments revealed that the new cap added a lot even harmonics to the point that they dominated the odds and as a result folks preferred the new sound, even though the total harmonics and hash was increased at the measurement level, the dominating even harmonics made the thing sound better.
 

NorthSky

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There is no doubt in my mind and set of ears that low frequency measurements are essential in our rooms.
...Some form of acoustic balance from room treatments helped by judicious EQ.

Even the highest of the highest ultra hi-end sound systems use measurements to improve acoustics of the room.
Subjectivity alone cannot coexist without objectivity. The two go hand-in-hand togetherness.
You make a splice, a split anywhere in that chain of balance, and you're in a world of hurt. ...Way of speech, from the movie...Predator.
 

Blumlein 88

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no. belles mb200, the noise is super faint but its there, not on the other side\amp. those kind of buzzes could be anything i guess. its just pain to be left with it, not knowing why.

It would help if we heard it. If you have no other device, could you take a smartphone and record a bit of it? Then post a short mp3 of the sound. That also lets you use software to see what frequency it is. Now many phones have nearly nothing below 100 hz. Still worth a try and we might help figure out what it is. Certainly sounds like an amp issue. Of course it could be what feeds the amp. If you leave speaker cables alone and swap amp input leads does the buzz stay put or swap sides?
 

Sal1950

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Easy test for issue 2,
First try just floating the ground on the power cord of the offending amp. If no improvement then turn the plug around reversing the hot and neutral prongs and listen again. May have to file the wider prong to do this.
Good luck
 

Thomas savage

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yea i have done all the problem solving\identity things. its the amp but its very faint. i tried recording it with my phone(not a smart phone) but no joy. you can't hear it with the preamp on, its hiss masks it. i have had millions of issues with hi fi over the last few years. it just strikes me a more measurement based diagnostic methodology from the guys selling these things would be great. dealers should measure these things and the mains supply and you room, to get a better picture of what the are working with, rather than just dump stuff down and bugger off. i might as well of gone the DIY route as every problem i have had has been met with incompetence imo. its always a mystery and someone else's fault, so you have to solve yourself.. but i am not qualified to do this and it always results in stress and confusion.
 

Thomas savage

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Easy test for issue 2,
First try just floating the ground on the power cord of the offending amp. If no improvement then turn the plug around reversing the hot and neutral prongs and listen again. May have to file the wider prong to do this.
Good luck
i can't float the ground as this puts volts on the case work (using ballance power but i dont understand why this happens). i an not filing things lol but thanks anyway:) nothing is out of phase or wired up wrong, i have stripped out the wiring on the amp and gone through the thing but no result.

i think i solved\elviated problem 1. yesterday, i took out one of my passive filters (russ andrew abzorber) its some like of clamp spike absorber but maybe it dumps onto ground like so many of those things do.. i took it out and problem so far seems to have gone. this device seems to attenuate the top end some how.. weird.
The AbZorber is a unique mains filter combined with spike clamp that works within normal mains voltages to reduce the effect of spike activity. Our SuperClamps and MegaClamps work by clamping surges over about 340V; AbZorber works by reducing the residue of these spikes at lower voltages – no other product does this. For the best performance improvements, use the AbZorber in combination with our SuperClamps, MegaClamps and Mains Purifiers.

i can open it up and take photos if anyone is interested but they have painted all components black.
 
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Sal1950

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i can't float the ground as this puts volts on the case work (using ballance power but i dont understand why this happens). i an not filing things lol but thanks anyway:)
No problem. With the very high sensitivity of my LaScala Horns combined with the high input sensitivity of my VTL amps. .750 mv IIRC I found power polarity easily audible as noise in the speakers and had to check each component to get it to a minimum. System was never totally silent but had to put my ear to the speakers to hear anything when all was at it's best. When thru a lot of input and driver tubes though. :)
 

Blumlein 88

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No problem. With the very high sensitivity of my LaScala Horns combined with the high input sensitivity of my VTL amps. .750 mv IIRC I found power polarity easily audible as noise in the speakers and had to check each component to get it to a minimum. System was never totally silent but had to put my ear to the speakers to hear anything when all was at it's best. When thru a lot of input and driver tubes though. :)
I have seen several systems like this. Too much gain. In VTL's it is pretty easy to put a divider network in the input that will cause no other issues. Knock out some of that gain. For a time when preamps were commonly used by everyone many tube pre's had very high gain, and fed tube amps with very high input sensitivity. You wondered how that was true for so many systems.
 

Sal1950

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I have seen several systems like this. Too much gain. In VTL's it is pretty easy to put a divider network in the input that will cause no other issues. Knock out some of that gain. For a time when preamps were commonly used by everyone many tube pre's had very high gain, and fed tube amps with very high input sensitivity. You wondered how that was true for so many systems.
Yep, I ran a Steve McCormack totally passive line drive there, a very synergistic pairing and dead quiet in and of itself. Still plug polarity of things like my phono amp, cd player, etc was audible.
 

Blumlein 88

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First is honest comprehensive measurements of the conventional kind. Not marketing based measures that leave out what is inconvenient. Following all the AES17 standards guidelines for audio measurement is a good start.

Among review publications Stereophile's measurements can be quite useful if you know what you are looking at.

I remember when Audio magazine published this yearly equipment guide. Had nearly all consumer playback products with specs listed. I remember seeing Magnepan speakers. Funny room divider looking panels. Specs on FR were like 50-12000 hz +/- 5 db. And they were expensive. I had never seen or heard such things. Wondered why anyone wanted such things when so many speakers were listed as 20hz-20khz or 30hz -20 khz. Some even adding +/- 3db (must have been using 3 octave smoothing on those measures). In time I actually heard some of them. It became clear, for speakers those listings were make believe. Magnepan was simply being more or less honest.

I remember cassette decks listing 30-18khz +/- 3 db specs. Eventually I came to know what that really meant was +0 to -6db frequency response numbers if they were even telling the truth. Listen to a Nakamichi with 20-20,000 +0 to -1 db specs and the difference was obvious. Plus most Nak's exceeded the spec somewhat when tested.

So simply getting real measurements without leaving out things to mislead is a big step in the right direction.
 

March Audio

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i can't float the ground as this puts volts on the case work (using ballance power but i dont understand why this happens). i an not filing things lol but thanks anyway:) nothing is out of phase or wired up wrong, i have stripped out the wiring on the amp and gone through the thing but no result.

i think i solved\elviated problem 1. yesterday, i took out one of my passive filters (russ andrew abzorber) its some like of clamp spike absorber but maybe it dumps onto ground like so many of those things do.. i took it out and problem so far seems to have gone. this device seems to attenuate the top end some how.. weird.
The AbZorber is a unique mains filter combined with spike clamp that works within normal mains voltages to reduce the effect of spike activity. Our SuperClamps and MegaClamps work by clamping surges over about 340V; AbZorber works by reducing the residue of these spikes at lower voltages – no other product does this. For the best performance improvements, use the AbZorber in combination with our SuperClamps, MegaClamps and Mains Purifiers.

i can open it up and take photos if anyone is interested but they have painted all components black.

do the components look like these?

http://au.rs-online.com/web/c/passive-components/variable-resistors/metal-oxide-varistors/?sra=p&r=t
 
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