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Microphony III

Discussion in 'audio' started by BE718, Jun 29, 2015.

  1. BE718

    BE718 pfm Member

    Note that its not an issue (assuming it is) that can be addressed by a stand.

    See how my amp case resonated in the graphs. You address (assuming it is an issue) this by damping (or changing the mass/stiffness) of the case and any potentially sensitive components inside.
     
  2. BE718

    BE718 pfm Member

    John please stop! Please read the document. They are recommended LIMITS based on human exposure. They are not measurements of actual vibration levels in those environments.

    You iphone is completely inappropriate and inaccurate for measuring this sort of thing. Give it up.

    BTW human vibration is something my company does assess. When I was working in the acoustics department performing occupational noise surveys I did spend an interesting day riding around in various infeasibly large mining trucks in the Pilbara measuring noise and human vibration levels for the drivers.

    Yep Ive done that too.
     
  3. Steven Toy

    Steven Toy L3 Toy

    There's a thing; it doesn't drive me to distraction. I just accept it and enjoy any improvement.

    The first two paragraphs above are pure objectivist clichés.

    1) Extraordinary claims requiring extraordinary evidence.

    2) The 'foo' versus 'science' dichotomy.
     
  4. BE718

    BE718 pfm Member

    If you really did just "accept it" you would live with the tiny effect and not spend thousands on special stands and plastic clips trying to improve the situation. So sorry, I dont buy that. In fact it seems obsessive. What were you saying about Tony having a healthy perspective?

    It also is somewhat bizarre and irrational to focus on this when they are huge gains to be found by looking at and dealing with your room acoustics. The problems of your room acoustics is something you seem to be incapable of noticing !

    There is nothing clichéd about this. We have simply technically evaluated your claims. Sorry, they simply dont add up.

    The web site of the manufacturer of your stand is full of technically inaccurate claims. Foo, pure and simple. The mains board should win awards for creative fiction writing.
     
  5. Steven Toy

    Steven Toy L3 Toy

    I really don't think you get it at all because you can't measure what I hear. What is more, the effect, whatever it is, is not something you notice until it is reduced and when it is there is a subtle yet worthwhile improvement in the music itself as opposed to gross differences in the noise.

    I call it upgrading and I derive enjoyment from it from time to time. I probably upgrade something on average once every six month or so.

    I've spent a few hundred and certainly less than £1000 over four years or so. I bought one of only three of these stands to have ever come up second-hand. None of these three were sold because their original owners derived no improvement from using them. The stand I had previously evolved over 11 years.

    I do not obsess over perfect hi-fi because such a thing doesn't exist. I accept that. I just enjoy the subtle improvements that enable me to hear what the musicians and producers were doing in the recording. Gross in-room stuff doesn't bother me unless it's really bad, in which case I'd move house.

    If you want to delude yourself into thinking that you are going to get perfect hi-fi by measuring and EQing, carry on!

    It's a free world :)

    However, please desist from using the Royal 'We...'
     
  6. westsea

    westsea Retirement present

    Accepted, but I was thinking of the resonance of the stand, and possibly the system, comprising the stand and amp. As you say the amp, or its case, has a resonant frequency of about 300hz and it is measurable. But that doesn't tell us the natural frequency of your stand which looks very rigid compared to Steven's. I am trying to understand why Steven's system can be made to actually sound different due to its unique characteristics.

    PS Perhaps a weakness of the amp design not to add damping to the case
     
  7. Steven Toy

    Steven Toy L3 Toy

    I don't think his customers need such nannying.
     
  8. Purité Audio

    Purité Audio Trade: Purite Audio

    Candidly, what does John believe is the best sounding support, wood and if so which ,metal,
    steel or aluminium perhaps, or does he plump for something really unusual, grapefruit segments perhaps?
    Keith.
     
  9. BE718

    BE718 pfm Member

    Steven, you are confused about what has happened here.

    You make a claim about stands isolating vibration and improving the sound of your amp. We examine the science behind that and find that a stand is going to make very little if any difference to the vibration in the equipment. The stand has no intentionally designed mechanism for isolating vibration. In fact what you have done, taking the feet off of the equipment and rigidly couple it to the stand is precisely the wrong thing to do to minimise vibration.

    Thats all thats happened, I have not once said you dont hear differences. I have however questioned the source of the differences as they are clearly not what you think. Having an open mind I also pose questions regarding the psychological aspects of an individuals perceptions. I have also suggested controlled blind listening tests to investigate this further.

    You object to all of this because the scientific reality doesnt tally with your beliefs. So please quit the nonsense about me only understanding or accepting what is measured.

    "Gross in room doesnt bother me unless its really bad". I hope that was just a poor choice of words. The point is that it is bad, but you seem to wilfully choose to ignore it - you seem to have no belief in it.

    Moving house wont solve the problem, that shows just how much you dont understand room acoustics.

    Do I need to point out that you have never heard your room without its acoustic issues? and you talk about "its not something you notice until it is reduced" oh the irony :) The difference is that the effect of sorting out your room acoustics isnt in any way subtle.

    Why do you suggest I have a delusion regarding getting perfect hifi with room EQ? Where have I suggested any such thing? Room EQ is just a tool for dealing with a problem where passive methods are neither practical or desirable. Its obvious that you are just idealogically against it.
     
    YNWOAN likes this.
  10. BE718

    BE718 pfm Member

    Grapefruit segments might work quite well ! :D
     
  11. BE718

    BE718 pfm Member

    The stand was being excited by the same acoustic source as the amp, but wasnt showing much of a response if you look at the graphs.

    If you check in part 1 of this thread I did perform a bump test on the stand to demonstrate its natural frequencies. You are absolutely correct in thinking that Stevens plastic stand will have different natural frequencies. Its impossible to ascertain what without measurement. I am quite sure that the stand designer didnt perform FE analysis on it :D

    Interesting to note that my stand, a notionally bad metal and glass type, didnt vibrate very much, significantly less than the amp. All you need to do is help the isolation between stand and component with a compliant coupling....definitely not rigid.

    The amp actually does have some damping on the underside of the case lid. Its resonant response would be worse without it, however we really need to put this into context, the vibration levels are spectacularly small and enough has been done to make it a non issue. I also think that the damping has also been added for creating a higher quality feel to the amp. My Onkyo AV amp when tapped sounds like a tinny piece of crap, the Tag doesnt.

    You need to think of the amp and stand as separate components WRT vibration. The amp is doing its own thing.
     
  12. Purité Audio

    Purité Audio Trade: Purite Audio

    I am an advocate of citrus fruit isolation, but woe betides the man who chooses crunchy Granny Smiths!
    Keith.
     
  13. Tony L

    Tony L Administrator

    The 'smallness' is interesting. I'd have thought that if I could feel vibration in my CD player, which I can (as mentioned it is rather close to a very big Tannoy), then surely that movement is going to be larger than say the gap between pits on a CD? Again I'm not implying any cause/effect here as a) the player has a suspension within the case, and b) it works anyway. I'm just suggesting that spectacularly small vibrations may be significant given the size of what one is measuring/reading in both vinyl and CD replay. It would be very interesting to try and find a CD player with an error counter, e.g. something like the old multi-box Cambridge CD1, and see if a support change could alter the error-correction count.
     
  14. BE718

    BE718 pfm Member

    It might be interesting to measure the natural frequencies of your CD case. Ive said all along it has the potential to be a big issue. My measurements confirm that the stand is not really the big issue here.

    All cd mechanisms I have seen have vibration isolation with compliant coupling. Secondly the vibration of the disc, the out of balance forces and modal pattern will be greater. thirdly, CD has error correction, fourth, if you are still convinced its an issue, move over to streaming!

    A a slight aside to this its interesting to note that CD ripping software such as DB poweramp generate a checksum from the extracted data. This is compared to that of other peoples rips in an online database. Its purpose is to confirm your rip is error free on the basis of this comparison. If everyone has the same checksum, the extracted data is obviously accurate. The hundreds of rips I performed were all accurate. This is even with the rom drive going x times faster than a normal cd.
     
  15. BE718

    BE718 pfm Member

    LMAO!:D
     
  16. John

    John Fore!

    His measurement of 0.1 micron displacement for the largest measurement seems quite small and humanly impossible to feel.
     
  17. BE718

    BE718 pfm Member

    John, with respect you need to do some research on the subject of vibration before you offer opinions.

    I will try for a third, or is it fourth time to get a concept across to you regarding frequency and its effect on velocity and displacement.

    When converting between acceleration, velocity and displcement the integration and double integration dramatically reduces the amplitude levels with increasing frequency.

    I will let you think about that and the reason why I tested at 300Hz.

    As an aside, have you ever wondered why your woofer moves so far and your tweeter doesnt? Its not just because you cant see it because its moving faster.


    BTW that wasnt the largest measurement, it was at a considerably lower acoustic pressure of 70 dB(A). Take yet another look at the data.
     
  18. adamdea

    adamdea You are not a sound quality evaluation device

    BE I'm really grateful for your input. I'd honestly advise though that you give up trying to persuade people to see sense. To be brutally honest lots of people aren't interested in reading anything that doesn't match their preconceptions. The whole function of sciencey sounding stuff is simply to validate the hobby experience. Eventually you will burst a bloodvessel if you assume that you will eventually get through to someone who is talking round in a circle throwing up daft points which indicate that they haven't listened or understood more of less anything you have said. If someone asks a question and then proceeds to post on ignoring your answer it's a giveaway.

    I say this not to dissuade you from posting but in order to preserve your sanity and to discourage you from giving up altogether.


    There is very little coming up that has not been covered by the following, which I think follows from what you have said [do correct me if I have misunderstood]

    1) most vibration coming from sound playing in a room comes through the air. if I have understood correctly, you can't stop that vibration using any stand.

    2) You can't effectively stop vibration coming from the floor using a rigid stand.

    3) you can't, using a rigid stand, drain from a component the vibration coming though the air or coming from the component itself .

    4) solid state components are not really affected by vibration anyway, if they were it would be common knowledge in the design of pretty much all sensitive electronic equipment not just the ones with moving parts.

    5) if they were affected in this way, and for other things which really are affected, like turntables and maybe valves, in order to isolate or reduce the effect of vibration you need a specific design strategy based on compliant coupling , damping and/or changes to the effective mass of the thing you are protecting which will have to be based on specific properties of the thing you are protecting and the frequencies of concern

    6) stands which are not designed in this way can only have either no effect or at best a random effect as they might change the amount or quality of vibration coming through the floor, but not eliminate or probably reduce it. Most of the time they probably have little effect. However, even then, let's not forget 1)

    And here's one of my own. if points 1) to 6) are correct then it seems to me that if you identify a particular stand (and certainly one not not designed as per 5)) having a particular sound with pretty much all equipment (perhaps to a greater of lesser extent) then your identification is unlikely to result from a genuine physically generated effect.
     
  19. IanW

    IanW pfm Member

    That is good progress. Interested to read of further progress and any results and conclusions.
     
  20. Sue Pertwee-Tyr

    Sue Pertwee-Tyr Well, I can dream, can’t I?

    This thread has been interesting, and thanks to BE for all the food for thought. I have a few, probably not particularly helpful, comments.

    Firstly, with regard to Keith’s perennial remarks about something not being properly designed. I realise this is normally trotted out without a moment’s thought mainly to get a rise out of somebody, but it does seem to me that he may be making assumptions about the design criteria which he might not be entitled to make.

    Not being an electronics designer (no, really), I’m not qualified to comment, but ISTR John W and others, who are, have said that, for example, power supplies can be susceptible to electrical noise, and/or that if you apply too much regulation to a power supply, sound quality suffers.

    What this tells me is that ‘proper design’ takes into account measures to reduce susceptibility to external influences but also notices if those measures themselves adversely affect the overall performance of the unit in terms of the overall design aims (eg best SQ for the cost), and adjusts the compromises accordingly. Keith’s rather blunt assertions make no allowances for such things.

    So, if the designer observes that his unit works better with decent mains, or sounds different on different surfaces, he might be able to design-out that susceptibility but if doing so results in a unit that sounds like it is playing underwater, then it’s perhaps preferable to accept the quirks. Depending on your budget, you may have more or less scope to work on solutions. That's different to 'correctly' and 'incorrectly' designed, which does sound a bit Soviet in its unequivocality. Are we to expect 'an amp designer's response to just criticism' at any point, perhaps?

    Just saying.

    And my second point is that while BE has been careful to argue that ‘you imagined it’ is simply a possibility which shouldn’t be ignored (on which he is undoubtedly correct), others have taken the ‘it’s not shown up in the vibration measurements’ to be tantamount to saying ‘it’s not been measured, therefore you imagined it’.

    Let’s just say that that conclusion does not follow from the evidence. Unless and until you can dismiss every other possibility, AND can show that the conclusion is one you have evidence to support, it's just a different sort of unsubstantiated supposition. Like, oh I don't know, like the ones about microphony are now slated as being. It is, I think, quite rare for anybody on here to be sufficiently educated and experienced in both electronics AND human perception, so that they would be qualified to make these definitive statements.

    In short, if you want to rely on a claim that those reporting changes to the sound have imagined those changes, then under the usual rules we’re entitled to ask for your evidence and supporting arguments. Otherwise, it is only your opinion, just as ‘I heard it, and can’t explain it, but don’t think it is all psychoacoustic trickery’ is only my opinion. So please stop using 'you must have imagined it' as an argument unless you have the knowledge and facts to be sure of your ground. It’s only what you ask of others, after all.

    Bear in mind also that, certainly the way it is expressed by some, ‘…therefore you imagined it’ can be a highly pejorative comment. Basically, the way some posters deploy it, they are accusing somebody of hearing things, and we all know that hearing things that aren’t there is what mad people do. They are, in effect, accusing somebody of being crazy. They never come out and actually accuse people of being mad, but you’d have to be pretty dumb not to be able to read between the lines to what they are implying.

    That’s the bit that generates the heat in these threads, because the targets of the argument are quite reasonably annoyed at being told they are mental –the poster might try to deny that that was what they meant, but it’s a bit lame. So even if it is the accused who raises the temperature of the debate in retort, the provocation has come from elsewhere (hint: and not from the intellectual or moral high ground).

    To return to the OP, I’d still like to know what is going on. If it isn’t microphony (at least in the terms investigated here, and I did suggest some enquiries which haven’t taken place and no doubt there are others) then what is it? Psychoacoustic suggestibility is, of course, one possibility, but you won’t prove it by a process of elimination. Nor will you eliminate it by making people doubt the evidence of their ears.
     

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