Talk:Audio system measurements

Merge
I'd rather this article was not merged with Audio quality measurements as I started the latter, and it's associated series, after looking at this one an deciding that it was beyond hope! I say that because it muddles ideas of system measurements with quality measurement and goes on to say that measurements do not measure quality!

While I agree that listening is always important, I and many others regard audio quality measurement to be about exactly that. If it doesn't work, then that's because you are making measurements that were not designed to measure audio quality as subjectively perceived. I believe that professionals in the UK and Europe had this sorted out decades ago, with the development of weighting curves based on subjective experiments, but that the US has yet to realise this. I'm quite happy to discuss things, and to work to improve this article, but until I have time to do that I'd appreciate it if the intentions of the one I started (to give a proper UK/European professional understanding of the term) were understood and preserved there. I know that many of the things said in this article are commonly stated ideas, but since they are easily shown to be wrong, they would be better stated perhaps on a page entitled 'common audio misconceptions' (with explanations as to why they are so), which I have considered starting --Lindosland 00:59, 21 March 2006 (UTC)


 * Sounds like a POV fork. — Omegatron 02:39, 21 March 2006 (UTC)


 * This article is not about quality measurements, and doesn't claim to be in any way. It's purely about quantitative measurements that are usually made and quoted in specifications. At least that was the original intention - perhaps some other editors have confused the issue since the initial text was drafted, in which case a cull is probably in order. However, since this is not about quality measurement, I don't think a merge makes sense anyway. Graham 04:42, 21 March 2006 (UTC)

I have put up merge banners. This does not look like it will be a difficult merge. I see no justification for separate articles in the content of the articles. Only justification is on the talk pages. --Kvng (talk) 14:23, 15 October 2010 (UTC)

Hi, this article has still not been merged. At this point, the content of this article is so far behind that of Audio system measurements it would probably be quite easy to merge. IF no one objects, I will do this eventually. Michaelgaccount (talk) 04:44, 27 June 2012 (UTC)


 * I've now merged the only substantial content in this article into Audio system measurements. I'm going to go through and clean it up some more, and then I'll delete this article.  If you're like to help, please feel free to edit.  152.3.41.65 (talk) 01:06, 28 June 2012 (UTC)


 * Merge completed. Source article now redirects here. --Kvng (talk) 02:39, 2 July 2012 (UTC)

RMS Power is WRONG!
As an example I will take this, which at first site is a correction of a commonly abused measurement. Yes, PMPO is nonsense, never defined anywhere, and number one hated term to be erased from a million advertisements (which seem to take power and multiply by a factor chosen at whim). RMS power though is also wrong, since without a definition of the test waveform and the averaging period (root MEAN square) it has no single meaning. Power in a steady state system is indeed calculated as rms, but its the VOLTAGE that is squared, averaged, and rooted, not the power! There have been many articles pointing out this simple error, and also pointing out that if you actually take a 1w (sinewave power) amplifier and calculate the RMS of the power over the cycle, the answer is not 1w but something a bit bigger! The correct term (almost never used) is 'max sinewave power'. Driven with a squarewave, a 1w amplifier will give 2w (of actual 'true' power!) out, which serves to make the point that its the waveform that we must specify, by convention, and nothing to do with rms, or even 'true' power. --Lindosland 01:10, 21 March 2006 (UTC)

Sophisticated quality measurement
Following on from my above comments, and my emphasis on proper techniques, I would point out that it has recently become possible to make sophisticated measurements on a total system, including CODECs like MP3 based on real-time computer emulation of the human hearing process as we now understand it, including temporal and frequency masking, level-dependant frequency response, in line with the equal-loudness contours and proper combination of hair-cell responses across the band. These give good agreement with subjective assessments. Things have come a long way since basic engineering measurements were deemed not to give meaningful results, and this article should make that clear, rather than perpetuating the wrong idea that basic measurements are the same as quality measurements. I'll try to look up material in the recent AES papers. --Lindosland 01:46, 21 March 2006 (UTC)


 * I agree with everything that you're saying, though the opening paragraph of the article does make clear that these basic measurements are NOT an indicator of quality and shouldn't be taken as such. A quality system will have good measurements; but a poor one can also have good measurements. What you're saying above about 'total system' measurements is very interestign and should definitely be mentioned - how about a new section called "Recent developments" or somesuch, and add it under that? By the way, as far as RMS power is concerned, most people would assume that unless otherwise specified this means sinewave power, usually at 1kHz. Graham 04:38, 21 March 2006 (UTC)


 * Yes, I know they would agree, but few would realise that there actually is such a thing as RMS power and it's not what they think it is, it's something else, and pretty meaningless, hence the use of the term RMS should be stamped out! I'm not sure you get my meaning regarding quality measurements. While there are some system measurements that are not intended to be a measure of quality (like output power, or playing time) many system measurement like THD are used as if they in were test of quality when they are not what I would call 'quality measurements'. Quality measurements are a measure of quality, by definition they are designed as such, based on subjective testing. Obviously no single quality measurement is a guarantee of quality, but taken together I would say that they are indeed a guarantee of quality, with the proviso that if the source is encoded (MP3 etc) then they are only a guarantee that the result will be the best quality possible for that codec, the codec itself requiring more sophisticated tests, such as I have outlined. You say that 'a poor system can have good measurements', and here I disagree, though I think fundamentally we probably do agree. Most commonly, it is of course said that a system can have low THD (say 0.1% or less) and still sound distorted. My answer is that THD is a mathematical concept, not a 'quality measurement'. Lindos use and recommend 'Distortion Residue' measurement, and after much testing and demonstrating using our 'corruptor' which I designed to simulate various defects when inserted into a system (including crossover distortion), I claim that if a system measures -30dB (0.3%) or less on the Dist Res test then it will sound clean, to anyone, whatever it is, power amps included (assuming certain other things like digital jitter are also within bounds). I test using equipment to the very highest standards on Quad and Mackie monitor speakers, and the point is that the measurement uses weighting and quas-peak detection for proper results. This is a far more sensible approach than just aiming for ever lower figures of THD without ever being able to say how low you need to go! I would like to see this page rewritten to eliminate all suggestion that 'system measurements' have anything to do with quality, but pointing out that there does exist a subset of system measurements, described as quality measurements, that do indeed, taken together, give an assurance of quality (that's why broadcsters use them). A link to Audio quality measurement should then take them to a proper description of such measurements. Incidentally, Lindos Electronics has introduced a quality grading scheme, which is outlined in the MS10 user manual, but will soon be written up more fully on the website. To see this in action take a look at (i-Pod test) or  (Sonifex 96k 24-bit ADDA) or the many other items on the Test Result Database tab. --Lindosland 20:13, 22 March 2006 (UTC)


 * This isn't Lindos Electronics; this is Wikipedia.
 * Every "audio quality measurement" is also a type of audio system measurement, is it not? — Omegatron 22:29, 22 March 2006 (UTC)


 * Taking THD as just one example - no-one is claiming it's a quality measurement - it's a pure quantity measurement, and the instruments that measure it treat it as such, with no subjective weightings, etc. They merely measure the ratio of 'wanted' to 'unwanted' signal (however you define those). If you read a system specification and decide that an amplifier with 0.1% THD is of higher quality that one with 0.5% THD, then you are deluding yourself, and falling prey to the marketers who publish such specs precisely because they mislead the uninformed in this way. The only proper way to judge quality is a listening test, but let's be honest, the mass market doesn't bother and manufacturers know this, therefore the specification is there as a kind of "quality measurement by suggestion", just as car manufacturers say that their model can do 124 mph compared to their competitor's 119. It's all totally irrelevant but marketers know it does persuade buyers nevertheless. However, this all has nothing to do with the article - the article lists quantity measurements and what they mean. It's not for us to tell people to take these with a pinch of salt, that applies to anything. Your company does something different and we suppose, something more meaningful or honest; good for you. That has nothing to do with this article or what it sets out to explain. You say that the article should be rewritten to remove any suggestion that these measurements have anything to do with quality - I say, re-read it and you'll see that already it makes no such claim, and indeed goes out of its way to make this clear. Graham 09:22, 23 March 2006 (UTC).


 * 'Your company does something different .....that has nothing to do with this article.' I think it does, because this article is based on the idea that measurements should not be used as an indication of quality. I say that's wrong. It's a relic of the past, before specific measurements were invented. Lindos Electronics represents the non-US way, which is not the same as saying it does it's own thing. Also Lindos Electronics is not just one of many companies in its field - I would say it dominates the field outside the US as its equipment (the LA100) is regarded as the 'de facto standard'. This is partly because Lindos invented 'segmented sequence testing', which is used routinely by most broadcasters worldwide (but not US). There's a real problem with US isolationism via 'Federal standards' and the hugh US voice doesn't realise what is going on in the rest of the world. That's why I appear 'pushy' when I am trying not to be. --Lindosland 11:12, 5 April 2006 (UTC)


 * I'm not sure where you get the idea that this is a US-centric article. I am British and originated the article based on my own interest and experience in the field. Others have added content since however. I may well be out of touch with current developments, but that doesn't mean what is written here is invalid - it applied at one point in history at least, and stands as a document of that era. There may well be an argument for further articles such as segmented sequence testing, with a brief mention and a link from here, but there's no real need to invalidate everything that has already been written on that basis, just as the existence of the Ford Mondeo doesn't invalidate the article about the Ford Model T. I think what is giving people trouble here is your obvious lack of impartiality, since however genuine your motives, the linking of your name to the Lindos company raises the question of a neutral point of view. Even if you are a saint (which, assuming good faith, I believe ;-) it would be unreasonable to expect you to remain completely unbiased. That's why it might be better to create spinoff articles and let them stand on their own two feet. I certainly have no objection to a brief overview and link here or other relevant articles. Graham 11:58, 5 April 2006 (UTC)

To merge or not to merge?
I believe that 'Audio system measurements' should not be merged with 'Audio quality measurments', simply because audio QUALITY can be measured or studied without an 'audio SYSTEM' involved (assuming that an 'audio system' is usually considered a combination of electronic and electro-mechanic devices, or at least a part of such a combination). A new, more general article 'Audio measurements' comprising both of the above articles would make sense, though.

Distortion measurement
Hi Omegatron. I see you have challenged the accuracy of the page I created on Distortion measurement, but you have not justified this on the talk page. I am all too aware that what I have written there is not generally understood, especially in the USA, but it is widely agreed, especially by professionals. I am in an unusual position here, because I have spent 25 years promoting 'proper' measurements, and am to some extent considered an authority on the subject. I could for example cite the prestigious 'The Audio Engineers Reference Book' by Butterworth Heineman, but then I wrote the chapter on audio measurement in it at the request of its editor, so is it fair to do that or not?! Tell me what you consider innacurate or wrong, and I am happy to discuss things (on Talk:Distortion measurement). --Lindosland 12:15, 29 March 2006 (UTC)


 * I'm sorry for tagging it and leaving; I haven't had much time to work on things lately, but it's still factually wrong regarding distortion and harmonics produced. I'll work on it when I have some time. — Omegatron 17:15, 29 March 2006 (UTC)

After re-reading I realised that this article was much more POV than I had realised, and remembered that I had written it for the Lindos website and had not gone through it sufficiently after transferring it. I've now had a major attempt at Wikifying and have removed the template. It inevitably retains what might be perceived as some bias, but then it is intended to balance the existing article at Audio system measurements. I've left the other template, pending discussion. --Lindosland 13:01, 29 March 2006 (UTC)


 * Thanks for working to remove the bias towards your company; I'll look at it later. I understand that you don't consider some of those measurements to be "quality" measurements, and I haven't had much time to look through your ideas in depth (weighted THD, etc.) but, when interpreted properly, the vast majority of people consider those to be "quality" measurements and use them as such.  Regardless, the two topics are so closely related that they belong in the same article, and splitting them is not "balance", but a POV fork.  The "balance" is better if both "sides" are all in the same place for comparison. — Omegatron 17:15, 29 March 2006 (UTC)


 * Fine, and thanks for prompting me to do it, as I want to get the balance right. While I understand what you are saying, I might question your 'most people understand ...'. Though most people are familiar with the Audio Precision test set, which tends to use the methods I condemn, it is a fact that Lindos Electronics started before AP existed (Tektronix tried to buy Lindos, and when I resisted some Tektronix workers left and formed AP - see Lindos site I think Lindos probably has more test sets out there in the world - certainly in broadcasting where we have many thousands now, and I am constantly told they are the 'de-facto standard'. I give due credit to AP, whose equipment certainly does a fine job of measuring in engineering terms to super low levels, but outside the UK I suggest that such measurements are made in development more than in quality testing. Of course the 'audiophiles' don't get to see the true picture, as they are less into broadcasting and studio environments, and I would like to make them more aware of the fact that true 'subjectively valid' measurements are in widespread use. I see recent moves by other firms towards my approach recently - some of their press releases look remarkably as if I had written them! --Lindosland 17:39, 29 March 2006 (UTC)


 * Regarding 'balance', I understand that preferred policy is to 'fork' on controversial topics rather than weaken the content by trying to balance. I would agree that its fair to start with a balanced reference to the fact that two approaches exist, but trying to mix the two becomes confusing and I prefer to then fork, hence my fresh start with Audio quality measurement. --Lindosland 17:39, 29 March 2006 (UTC)


 * Quite the opposite, actually; forking controversial topics is forbidden. See Content forking.  We depend on showing all sides of an issue in the same article and using consensus and the wiki process to distill stale back-and-forth arguments in favor of a sort of overall, neutral, fact-based, well-referenced viewpoint that everyone can agree with.  Individual editors' authority doesn't hold much weight here; we depend on references and third-party verifiable facts instead.  After all, we've had resident "experts" on audiophile foolishness, engines that run on water, surviving on only air and light, antigravity, etc.
 * All that said, thanks for all your contributions so far. The noise weighting articles are much better now. — Omegatron 05:41, 30 March 2006 (UTC)


 * I was wrong to copy your use of the word 'fork' for what I meant. I see that (quote from NPOV) "A POV fork is an attempt to evade NPOV guidelines by creating a new article about a certain subject that is already treated in an article often to avoid or highlight negative or positive viewpoints or facts." I am not suggesting evading NPOV guidlines, and I have been involved in discussions where evidence was given to me of the desirability of separating out viewpoints - so long as it is made clear than they represent only one viewpoint. We are not talking of editor POV here, but the existence of alternative 'schools of thought'. These exist all over the place. You will not find all schools of Psychiatry covered on one Wikipedia page - they are split off into Freud, Laing,and dozens of others. Nor does anyone attempt a page on Religion, and forbid the splitting off of Christianity, Islam etc! It just couldn't work.


 * Your reference to experts also seems wrong to me. You are referring to 'self appointed experts' but I was simply pointing out that I can give references that are regarded as authoritative but which I wrote myself!


 * I've no desire to 'plug my own company' (actually I don't own it now). I actually created my Lindos out of frustration with the confused state of audio measurement and have gone on to devote much of my life to trying to improve true understanding, and facilitate meaningful measurements by making equipment avilable at low cost that could make them (it used to be argued that no one used 468 weighted noise because only costly equipment could measure it, but I changed that). The opposition comes from marketing people, and I find that other 'experts' in the field all agree on this. There is no dispute among those truly involved in the subject, just resistance from manufacturers who want big numbers for their marketing folk. This problem comes up again and again in standards commitees and working groups. I see nothing wrong with trying to clear away the fog and show the true field as understood by those truly engaged in it. It occurs to me that if Medicine were to cover the 'majority view' then most of it would be about alternative medicine and herbal remedies (and even witchcraft), though medical professionals would reject most of that. This is similar. Audio is full of quacks selling  'snake oil' (like oxygen-free speaker cables)!


 * Distortion residue measurement is certainly not a form of THD measurement. THD is as misleading as RMS power, a purely mathematical concept that should be banished! I say this because there is no reason to suppose that audio systems generate harmonics. Digital system tend not to - in general they generate 'hash' that is at no particular frequency, and trying to pick out the harmonics and sum them RMS is just meaningless. So THD is a very special case of non-linear distortion in fact. Note that this is not just me plugging my idea. I've been involved in AES working groups and made contrbutions to standards bodies. This method of distortion measurement was included in IEC268 (though as an option) following pressure from me and others, as was the 468-weighted noise measurement (again as an option).


 * However, its the understanding that matters, and I'm glad you agree that my contributions make sense. --Lindosland 11:37, 30 March 2006 (UTC)

and I have been involved in discussions where evidence was given to me of the desirability of separating out viewpoints - so long as it is made clear than they represent only one viewpoint.
 * That's not the way Wikipedia works at all. Where did you hear that?  That's the way Wikinfo works...

We are not talking of editor POV here, but the existence of alternative 'schools of thought'.
 * Exactly. Two subtly different, but mostly the same, schools of thought about the same thing.  They belong in the same article.

but I was simply pointing out that I can give references that are regarded as authoritative but which I wrote myself!
 * Of course that's fine. But it's walking on thin ice socially to cite yourself as an authority, as explained in Autobiography.

There is no dispute among those truly involved in the subject, just resistance from manufacturers who want big numbers for their marketing folk.
 * Or maybe because the "typical" measurement methods work fine when applied correctly, or maybe for uniformity between the specs of different companies, or maybe because THD+N measurements are federal standards, or maybe...

''Audio is full of quacks selling 'snake oil' (like oxygen-free speaker cables)! ''
 * It certainly is.

RMS power, a purely mathematical concept that should be banished!
 * The term "RMS power" is a misnomer, but the concept of measuring average power is fine. You think there's something wrong with the concept?  It certainly isn't a single magic number that quantifies the quality of an entire system (none exists), but it's tremendously useful even by itself.

Digital system tend not to - in general they generate 'hash' that is at no particular frequency,
 * That's why you use other measurements to quantify digital systems. Just like your 1 kHz-only distortion residue test would miss crosstalk from USB transceivers.  Any measurement of a system only measures a certain type of problem; you need several different measurements to cover everything, and knowledge of problems that might evade measurement, too.
 * How is "distortion residue" different from a 468-weighted THD+N measurement? I'm not saying that it's a bogus measurement; it sounds very logical to me, and indeed superior in many situations.  But I don't see it as anything that warrants its own article or other special treatment compared to other measurement techniques.  You really think it's neutral to create a separate article for your preferred measurement technique that is advertised as the distinguishing feature of the products made by the company you started?  Your measurements are just variants on the measurements used by everyone else (which vary among themselves, too).  They belong in the same article.  If you still disagree, I'll nominate it for deletion as a content fork and we can see what the community thinks...
 * Also, do you mind if I move this discussion to Talk:Audio system measurements so others can comment? — Omegatron 05:56, 4 April 2006 (UTC)


 * Yes, I'm finding it hard to know where conversations are going on about me now! Lets all talk about this at Talk:Audio system measurements. Maybe I should have started there, but I just foud too much to challenge there and decided it was better to write from the non-US standpoint as a way of getting over the fact to you all that the US position is actually a minority one. I notice a comment above 'or maybe because THD measurements are Federal standards. If you think 'Federal' means anything to most of the world then I think you are wrong. We never use the word, we never use 'Federal' standards. We use IEC, DIN, BS, EBU, and ITU, standards, all now working together and considered international. Federal standards are an oddity, confined to an isolationist country that happens to consider itself a 'superpower'.


 * How is 'distortion residue' different from 468-weighted THD+N measurement you ask. It isn't, that's my point. It's not just my pet thing. But we'll never get widespread acceptance of a measurement that's such a mouthfull to say, so in Lindos literature I use the term Distortion residue and suggest that it might be useful if this were adopted generally. Someone has to start these things off, and Lindos is in a good position to do so. Being respected as specialising in audio measurement across the board I feel that it can do this where other companies that sell audio items could not. When Lindos recommends something it is because they consider it to be good, not because it is a feature of their equipment. The equipment has evolved through years of talking to all sections of the industry. If Sony recommended a method, it would because their marketing men favoured it - hence the Beta-VHS war.


 * I don't understand what you are saying about average power. I have not opposed that though I have pointed out that without the addition of 'sinewave' it has no meaning. I also pointed out that 'over one full cycle' is the best definition, though I would not add this to the term. Average, over any other period will always be different of course, though this is acedemic for longish periods. In this I am well supported by standards and other writers on the subject.


 * I am not convinced that the two 'schools of thought' if we call them that, belong in the same article. From where I'me sitting (outside the US) the two have not been considered valid alternatives, especially in broadcasting. 'A-weighting' is seriously flawed in that is neither matches the equal-loudness contours properly, nor reflects the way we hear noise, as opposed to tones, yet it is used in the US to measure noise. That's wrong, and most of the world decided it was wrong thirty years ago. A-weighting is coming back here now, mostly in the consumer and high-end audio markets, which is why I am keen to fight what I see as retrograde influence from the US, via big manufacturing organisations.


 * I certainly do not agree about 'different measurements for different equipment'. Yes, some equipment needs measurements that we need not bother with on other equipment. For example we need not measure wow and flutter on digital systems generally becuase we know that it will be vanishingly small, but when it comes to noise in particular, we do now have one measurement that allows sunjectively valid comparison regardless of equipment type, and it makes a lot of sense to use it. I would not claim that Distortion Residue catches everything, but I do think it is more useful than other methods by far, especially as it puts an end to the nonsense of crossover distortion and digital distortion measurements that are simply useless if measured THD (I think you would agree with this and know that many others would). Regards --Lindosland 10:43, 5 April 2006 (UTC)

Lindosland replies - you've got it all wrong!
These 'Lindos preferred measurements' happen to be to the International and European standards (as quoted all over the place in the articles). It is a fact that such standards are not widely understood or adhered to in the US. Lindos has agents in most of the world, but withdrew it's full time representative from the US because of this problem. He felt he was wasting his time in the face of ignorance. The US is well acknowledged as having been 'isolationist' in buying little from abroad until recently. Trying to mix European and US methods in this field is like trying to mix Islam and Christianity on one page - it isn't to be attempted. Most Wikipedians are, I suspect in the US. I therefore ask you all to think carefully about this before undoing my work.

I can be fairly confident is saying that most of the world's broadcast networks are routinely tested for quality using equipment designed by me (mostly the LA100). This includes the BBC (several million pounds worth) BT (ditto) BSB Sky, Independant Radio (ditto) and TV throughout the UK, plus the major broadcasters in France, Germany, Australia, South Africa, Japan, and so on, but not in the US! The BBC does all its automated testing across its entire radio network regularly using the Lindos LA100's. A few years ago I was invited by the editor of 'The Audio Engineer's Reference Book' (pub. by Focal Press), to write the section on Measurement. The introduction refers to "articles all written by world experts". I have been invited to give lectures to BBC and other organisations. Training schemes were set up in the BBC to train all engineers in the use of the LA100 and Lindos was paid to provide the on-site training. Lindos were contracted to design and make special test equipment for use in the BBC, the IBA, and other broadcast organisations. "Clearly biased" and "products that measure his way". Sorry but you've just got no idea! You may think that the AP systems set the standard. Excellent though they are for measuring to low levels (we have one), in most of the world, most of the time, they don't. And Lindos was around long before them, or Neutrik. Up until now I have tried not to shout about my role in audio measurement, but I think now I have no choice but to point out that I am proud to have had a major influence on the field. --Lindosland 23:15, 4 April 2006 (UTC)


 * There's nothing wrong with the measurements. What's wrong is the way you're presenting them and the way you're editing Wikipedia.  Please read through the policies we've pointed you to.

He felt he was wasting his time in the face of ignorance.


 * Wikipedia is not a soapbox. — Omegatron 23:42, 4 April 2006 (UTC)


 * I've read everything you pointed me to, and answered you, but if you just insist that I own Lindos and it's website when I don't what more can I do? Would you like it in writing from the owner of Lindos Electronics? I have kept to all the rules strictly. If you agree with the content but not the presentation then you should tackle the presentation, not get personal with me. --Lindosland 16:29, 5 April 2006 (UTC)


 * Who is insisting that you own Lindos? We're insisting that you're clearly biased and not capable of representing information in a neutral way.  You've already demonstrated that you have an agenda and are unwilling to compromise. — Omegatron 18:15, 5 April 2006 (UTC)


 * Alistair is - despite repeated telling that I neither own Lindos Electronics nor maintain its website (I have my own business and website as it happens):


 * Quoted from Wikipedia:External links: A website that you own or maintain (unless it is the official site of the subject of the article). If it is relevant and informative, mention it as a possible link on the talk page and wait for someone else to include it, or include the information directly in the article. Please do not restore the links yourself. AlistairMcMillan 19:46, 4 April 2006 (UTC).


 * There's nothing to say I must compromise if I believe I am right is there. I think the agenda is elsewhere. I note that AListair's talk has on it numerous accusations regarding unfair removal of links and personal vendetta. He has removed every link and citation I have put up on audio related pages, despite my protests supported by quotation of WP policy that they are of high quality and extremely useful and relevant. --Lindosland 20:09, 5 April 2006 (UTC)


 * You founded the business and your son currently owns and runs the business. At the very least you contribute content to the website, writing articles and contributing data to the test results database.  AlistairMcMillan 20:47, 5 April 2006 (UTC)
 * That information has been freely given by me, but you are still changing the rules to suit your own interpretation. They make no mention of family links, or of contributing data. Perhaps they should, but at present they don't. If my page was anonymous, as most are, non of this would have arisen. You can surely understand why I feel a bit annoyed that by volunteering so much information about myself I have come under attack from you. Does not my open approach deserve a more understanding response, with strict interpretation of the rules? I am no 'spammer' and I link only to things that are immediately relevant. --Lindosland 11:00, 7 April 2006 (UTC)
 * It is because of your open approach that I have avoided using the terms "spam" or "spammer" when discussing this issue with you. I may be wrong, but I don't think I've used them once concerning this matter.
 * That does not change the fact that you are linking to web content that you created on a website that you are involved in to some degree. Using yourself as a source on Wikipedia is wrong and linking the website of a company that you are involved in (even if the only current connection is through family links) is still wrong.
 * And I'm sorry if you consider this an attack, it was not intended as such. AlistairMcMillan 15:59, 7 April 2006 (UTC)

New Introduction etc
I thought it a good idea to write a new intro which makes clear the real distinction between subjectively valid quality measurements and basic measurements. Also a section explaining why they differ. Hope this meets with approval. I would still suggest keeping the other set of articles as they do go into much more detail that would be appropriate here. Note that there is an article on A-weighting plus a set on Equal loudness contours which I did a lot of work on, to balance the other one on ITU-R 468, and that all give a history together with benefits and weaknesses. This seems quite fair to me, and allows users to follow the whole story through in detail if they wish to. --Lindosland 17:56, 5 April 2006 (UTC)

Cone excursion
A recent edit by User:Howard Doctor replaced "Reducing cone excursion" with "Reducing a driver's bandwidth" as a method for reducing Intermod distortion (IMD). I hold that both are valid methods. I'm reworking the paragraph to include them both. Binksternet (talk) 15:39, 1 October 2008 (UTC)

Frequency response
I made some changes to the section on frequency response. The first thing I did was to write a short description of what the frequency response measurement means. The next thing I did was to remove some stuff about what happens if the frequency response is not flat. Below I've highlighted the text I felt needed changing:

The signal should be passed at least over the audible range (usually quoted as 20 Hz to 20 kHz) 'with no significant peaks or dips. The human ear can discern differences in level of about 3 dB in some frequency ranges, so peaks and troughs must be less than this'''. Much modern equipment is capable of less than ±1 dB variation over the entire audible frequency range. Rapid variations over a small frequency range (ripple), or very steep rolloffs are considered undesirable as they can correspond to resonances associated with energy storage which produce delayed echoes and hence colouration, or decreased quality, of the sound.''

Research by Toole has shown that changes in frequency response much smaller than 3 dB may be audible. His work focused on unwanted resonances in loudspeakers. He showed that a resonance with a quality factor = 1 and amplitude of 0.3 dB may audible on some signals. His work has also shown that resonances with a high Q (i.e., a resonance with a small bandwidth and relatively large amplitude) are often less audible than resonances with a low Q (i.e., a resonance with a large bandwidth and relatively low amplitude) [2 refs]. The revision above seems to imply the opposite, that rapid variations in frequency response (high Q) are less desirable (more audible) than smaller variations in frequency response (low Q).

I decided not to summarise Toole's work in the article. I thought that it was too specialised in this context.

Unquantifiable?
I've made some revisions to this section. What I've tried to do is improve the article by rewriting the section and adding references.

I've added references to articles in Audio Critic and Stereophile magazine. Audio Critic and Stereophile represent two different viewpoints on the usefulness of objective audio measurements. I've also referred to the work of Dr Floyd Toole. His work is relevant because he has linked objective measurements to the results of listening tests. Dr Toole used double-blind tests in his research. To try and maintain NPV, I've mentioned that there are other people who prefer to use non-blind listening tests (Stereophile magazine). Enescot (talk) 22:45, 4 May 2009 (UTC)

What "Audio system measurements" should and should not have?
The question of what should go here and what elsewhere interests me. I don't think the coverage of the subject is quite right yet here, so may I suggest it aims to:


 * list all the technical terms one may find in specifications for audio equipment, even "PMPO" (even though it is hard to pin such terms down, and we generally don't like them)
 * distinguish between (and warn about) some terms, e.g. the frequency range of a speaker may be quoted as 50Hz to 18kHz, yet the frequency response might be 110Hz to 11kHz plus or minus 10dB; distortion might be quoted as "about 1% at normal listening levels" (yep, I've seen it!) yet 10% at full rated power; some mention should be made of the value of graphs of parameters (e.g. to show cross-over distortion is significant at low volume levels, even though the distortion is only 0.02% at 20W (and then only at 1kHz into a purely resistive dummy load)
 * mention terms like "unconditionally stable" and some places that define them (note that different manufacturers will use teh terms differently; it is worth having several links and a range of definitions sometimes).
 * give examples for ratings, including what is common for "average" equipment, what is very good, and links to some research as to what is detectable by the human ear. There should be separate pages for what distortion is audible, what distortion is "pleasing", what input impedances are "standard", f-m curves/weighting systems for noise, and so on.
 * There is virtually nothing on how the measurements are made. There should be (at least) mention of some of the standard IMD tests, DIN standards, measurement microphones and anechoic rooms; ideally some links to articles on testing each major amplifier and speaker characteristic.
 * There should be at least a paragraph on relating the buzzwords of typical hifi magazine reviews (like "warmth", "spatial perspective", "speed") to technical, objective measurements (a bit of a difficult job, but somebody has to do it!). The gooblygook is relevant to the topic, even if it may be "unscientific".
 * I'm not sure whether this is the place to include CMRR and other characteristics of small subsections (e.g. opamps), but rather how this affects the overall system (although I'd be happy to see a table of characteristics of components mentioned, alongside the "externally noticeable" effect they have). Maitchy (talk) 21:47, 3 February 2010 (UTC)


 * Any of the above discussions can be brought to this article if there are verifiable, reliable sources to support them. Bring it on! Binksternet (talk) 22:49, 3 February 2010 (UTC)

Damping factor is not a relevant factor
Damping is only a factor as long as the signal is in phase with the electromotive force, which it rarely is. The damping effect is negligible already at two octaves above the resonant frequency.

Damping factor became a buzzword in the early days of solid-state amplifiers because it was something that tube amplifiers did "bad."

If damping factor was relevant for amplifiers, then transconductance (current) amplifiers should be really, really bad. They are not.

Damping factor is marketing. It is at home with Stereophile and the other audiophools. You know, the "golden ears" who claim they can hear the "sonic characteristics" of different metals (usually copper, silver and gold) in connectors and switches. Silver is usually said to sound hard or cold, and gold warm. Whereas copper sounds neutral. True story. — Preceding unsigned comment added by 89.253.73.146 (talk) 22:13, 14 January 2014 (UTC)

External links modified
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 * Added archive https://web.archive.org/web/20081016103114/http://www.aikenamps.com:80/NegativeFeedback.htm to http://www.aikenamps.com/NegativeFeedback.htm
 * Added archive https://web.archive.org/web/20070928214133/http://theaudiocritic.com/back_issues/The_Audio_Critic_29_r.pdf to http://www.theaudiocritic.com/back_issues/The_Audio_Critic_29_r.pdf
 * Added archive https://web.archive.org/web/20090122034000/http://stereophile.com:80/asweseeit/491awsi/ to http://www.stereophile.com/asweseeit/491awsi/
 * Added tag to http://www.almainternational.org/assets/Documents/WinterSymposia/InvitedPapersWS2011/temme-practical%20implementation%20perceptual%20rub%20and%20buzz%20distortion.pdf

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