Perhaps we can hear the effect of a cone pushing, better than a cone pulling? - perhaps music is equally push and pull, but it's the quality of the push that matters more, or perhaps we're just totally barking up the wrong tree.
Perhaps a single ended amp having one connection anchored to earth, with one end floating, is better than both ends floating?
Perhaps a single ended amp is just easier to get to work well.
Perhaps a single ended amp having one connection anchored to earth, with one end floating, is better than both ends floating?
Perhaps a single ended amp is just easier to get to work well.
First of all thank you for your apppreciated reply.
My first reaction is surprise.
However, I had spoken of the flame of a candle as an extreme example addressed to a member who seemed very resistant to other ones.
Frankly, after your statement, I don't know if that's a physically acceptable example in this case.
Also because frankly I had never done that experiment with a candle flame.
But I'll do it very soon.
I may have given a wrong example, I ignore it at the moment.
It could be that the flame of a candle has characteristics such as to be susceptible to the vibration of air molecules because the flame itself is actually incorporeal, it is immaterial.
If I were a physicist I would have answered you in a more learned way than this. 😉
But it could also be yet another explanation, who knows.
After all I only indicated something that is written wherever you look for it, because I remind you that the statement is an acquired scientific fact, and I don't necessarily have to be able to answer any question anyone asks me.
Also because at this point, I'm not at all interested in spreading a notion as if I were inventing it myself.
I didn't invent even a comma of what I indicated, let's be clear.
I only offered the example of a candle flame.
If I discover that it is a bad example I'll apologize for my inappropriate example, and we will have learned something more.
But everything else I have indicated remains unchanged.
Whoever wants to "believe" it will believe it, whoever doesn't want to believe it should please ask the authors of what is written in the books.
Anyway, let me do the experiment and let me find an explanation for the possibility that the flame is not a suitable medium for the demonstration.
In the meantime, I kindly ask you to repeat the experiment with a very thin and light strip of paper fixed only on one side in order to see if it moves instead.
Or a feather, if you want.
In short, anything thin and light, but that has a matter.
this can be related to a single supply And this can be done also with a push pull amp i.e. using a single voltage supply with a coupling cap at the output A very vintage solution going back to early '70s ?
and what about an output stage with a pair of same npn ? will they provide a more push than pull effect ?
Microphones, amplifiers, loudspeakers:
If a pure sine wave is used as the signal source,
then if there is any difference of the 'positive / compression', versus the negative / rarefaction, that difference is primarily 2nd harmonic distortion.
So, whether the amplifier is single ended, or push pull;
and whether the loudspeaker is two drivers side by side facing the same direction,
or two drivers side by side facing in opposite direction and wired in opposite phase,
then second harmonic distortion is still possible, no matter how minute that distortion is.
Some push pull amplifiers have more 2nd harmonic distortion than some single ended amplifiers.
Those old Generalizations are not always true.
More Push of the air than Pull of the air?
Well then change that, just reverse the connections of the amplifier to the loudspeaker.
These items have to be thought of as a complete system, they are not just isolated devices.
If a pure sine wave is used as the signal source,
then if there is any difference of the 'positive / compression', versus the negative / rarefaction, that difference is primarily 2nd harmonic distortion.
So, whether the amplifier is single ended, or push pull;
and whether the loudspeaker is two drivers side by side facing the same direction,
or two drivers side by side facing in opposite direction and wired in opposite phase,
then second harmonic distortion is still possible, no matter how minute that distortion is.
Some push pull amplifiers have more 2nd harmonic distortion than some single ended amplifiers.
Those old Generalizations are not always true.
More Push of the air than Pull of the air?
Well then change that, just reverse the connections of the amplifier to the loudspeaker.
These items have to be thought of as a complete system, they are not just isolated devices.
Ask yourself, for a 'central' condition of 100 (whether talking about the volume air behind a woofer cone, or the volume of air behind the eardrum), is the ratio 101:100 exactly the same as 100:99? Or are they slightly different?
I used to do these sort of experiments all the time:
Open up your favourite audio software tool (e.g. Audacity) and generate a pure sine wave, at say 200Hz. 10 or 15 seconds should be fine; 25% full scale amplitude or a little less to allow plenty of overhead. Then add to it another pure sine wave, almost exactly an octave higher but subtly detuned, e.g. 399Hz. Just for fun, the 399 one could be a triangle wave, square wave, etc., (it shouldn't matter, but it might!). Then listen to the output. Try various listening conditions like headphones, desktop speakers, louder, quieter, etc. Can you hear anything strange? Any warbling, or 'phasing' or vibrato-like effects?
The 200Hz pure sine wave should have zero interaction with the 399Hz wave or any of its harmonics, so what's going on?
Hi abstract,
I know my opinion may not be much worth since I'm not an engineer or a physicist and my reply is not as learned as I would sometimes like it to be, but in my opinion, for what it's worth, they cannot be equivalent.
However, I would still like so much to know how things really are, and even why...
AFAIK Perpetual motion does not exist and so any movement sooner or later will stop.
Therefore the forward/backward movement of the cone of a woofer will stop sooner or later for more than only one reason, I guess.
So, for what it's worth, in my opinion the second movement, forward or backward depending on the phase of the signal, will always be at least "a bit" less than the first one.
Not to mention the fact that AFAIK the cone of a woofer will also be intentionally dampened by the final amplifier.
I don't know what happens in the reality of natural sounds (acoustic musical instruments included, of course), but for sure, as I've already said elsewhere, the difference between producing a (natural) sound and reproducing a (recorded) sound is oceanic.
IMO
This I have duly done. I tested with the same piece of music as above and a 25Hz test tone from REW. I used 2 items for testing, some lightweight blue tissue paper popular with cleaners, and a long wide and very thin strip of silicone rubber as used for physiotherapy exercises. Both were suspended in front of the speaker such that at the maximum excursion of the cone during the test there was no physical contact. (around 2cm in practise)
The result? Both materials were excited by the sounds waves and moved in concert with the sound. Obviously at 1m away from the cone this movement would be completely imperceptible in my case. You would need a large sub and many watts to move something at that range.
I will read those papers closely as I suspect there is something funadamentally different about their experiment than from mine. I strongly suspect that that is why we see a different result and I would expect to find that both results are valid with the respect to the parameters used in each experiment.
The key point I think we have to keep in mind here is that large amplitude low frequency sound waves whllst NOT lanching air molecules across the room as 334 m/s must necessarily move the air molecules AS THE WAVE PASSES A GIVEN POINT, otherwise there would be no wave to propagate and the sound would not travel. In my case the amplitude of the wave is about +/- 5mm pk-pk to get visible movement of the suspended medium. Clearly when the compression of the air occurs on the face of the speaker cone, the air molecules at that position are both moved AND compressed on the leading edge of the wave and are then pushed back by atmospheric pressure on the back edge of the wave such thet the NET movement of the air is zero when the speaker returns to its rest position, but there must have been ~5mm air movement in each direction during the creation of the sound wave. This movement would be seen at each observation point you choose decaying in the usual square law fashion as the wave travels away from the speaker. At the end of the test, all the air will be back in its rest position.
I recommend taking a look at a preview from "Master Handbook of Acoustics" in Kindle if you have an Amazon account as this is all explained quite clearly there, figure 1.5 in chapter 1 is especially useful here, and clearly shows how what is seen by my observations is very much the expected result.
A similar example is given in "Acoustics and Psychoacoustics" in figure 1.2. Also available for preview in Kindle.
However, let me peruse those papers in more detail and I'll see if I can deduce where the differences lie.
"When sound waves move through the air, each air molecule vibrates back and forth, hitting the air molecule next to it, which then also vibrates back and forth. The individual air molecules do not "travel" with the wave. They just vibrate back and forth".
If as in my experiment the amplitude of "They just vibrate back and forth" being +/- 5mm would you expect NOT to be able to see the back and forth motion when the medium is suspended in the wave and all the air molecules are moving at least approximately coherently? (And the frequency is low enough that material intertia is not a problem, and likewise psersistence of vision doesn't come in to play.)
Needless to say, my experiment repeated at 500Hz in front of the midrange failed to elicit any visible movement, even at earsplitting volume. Again, I'd expect the same result at 5Khz in front of the tweeter.
Food for thought.
If as in my experiment the amplitude of "They just vibrate back and forth" being +/- 5mm would you expect NOT to be able to see the back and forth motion when the medium is suspended in the wave and all the air molecules are moving at least approximately coherently? (And the frequency is low enough that material intertia is not a problem, and likewise psersistence of vision doesn't come in to play.)
Needless to say, my experiment repeated at 500Hz in front of the midrange failed to elicit any visible movement, even at earsplitting volume. Again, I'd expect the same result at 5Khz in front of the tweeter.
Food for thought.
I continue to not believe in that.
Because it's not a question of power, power has been exaggerated in my examples, but it doesn't really matter.
This seems very surprising to me.
It may be a question of communication.
I 've done several experiments of this kind, except with the flame of a candle, and I've never been able to appreciate any movement.
On the other hand, even a very experienced member on this same thread confirmed that the paper strip does not move (I don't quote his comment just because I don't want to offend anyone's sensibilities, and then I already quoted his comment once).
You speak of "excitement", I do not know what to think anymore...
However, in this case, moving should really mean moving in the classic meaning of the verb.
And the strip of tissue paper has never moved for me.
So, when you say
you mean that you did not attach the strip of paper to the speaker cabinet, right?
Please note I'm not implying at all that I don't believe your report, I'm just trying to clarify what's not entirely clear to me.
Thanks for the suggestions, although I don't believe they can change things.
Unless when you say "excited" you don't mean "vibrate" (which doesn't mean "move") in which case everything would be clear, because if a medium vibrates it means that it vibrates, not that it moves.
In which case the vibration or resonance can be expected, since all is able to resonate and vibrate.
But not to move.
Just as an example, in my living room I have a cupboard where I keep dishes (glasses, plates, etc.) when I play "Beyond The Missouri Sky" by Charlie Haden on the double bass and Pat Metheny on the guitar I can clearly hear the glasses resonating at certain frequencies of the contrabass.
The edges of the glasses clink because they touch and resonate, but they don't move.
I'm already sure of that and, in my view, it is very important indeed.
Just because it is not a matter of frequency, since the sound propagates the same way whatever the frequency is.
Otherwise it would constitute a singularity, and on this Planet that is just impossible. AFAIK
I'm increasingly thinking of a misunderstanding in communication or in the method with which your experiment was carried out.
However, I'm sure that sooner or later, for the love of science that we seem to have in common, we will be able to pull the fateful spider out of its fateful hole. 😉
I seem to have been adding to the confusion here rather than helping to resolve it!I was regarding vibration and movement as synonyms since vibration is just a special case of movement, namely movement about a central position.
If we align on our terminology (and that would no doubt be helpful!) it would be be true to say that both the tissue paper and the silicone rubber exercise band vibrated very vigorously. There was some residual mvement at the end of the experiment as the materials returned to their rest position. This was artifact of imperfect alignment and not something to be unduly concerned about.
I would note that the spl I used for the experiment was probably over 100db, much louder than normal domestic listening.
You are completely correct, and this agrees with my results, that sound propagates the same way regardless of frequency and amplitude.
What I demonstrate is that at low frequency (25Hz in my case) and high amplitude you can see the sound wave being launched from the drive unit by placing thin material orthogonal to the direction of the wave.
This isn’t a hard experiment to do if you have a tool like REW or WinSpeakers, and especially if you have tone controls that allow you to boost the bass so that bass cone movement is much higher than normal.
At the volume I used for testing I wouldn’t want any glassware in the vicinity though!
I am hoping that this makes a bit more sense now. 🙂
Let me know if it doesn’t!
@ulogon , I think you're just overthinking it, and punishing yourself too much as well. The broader point is to have fun experimenting, and a lot of the forum members enjoy experimenting and learning about physics and electronic principles (etc) from the ground up. An engineering background may give advantages in some areas, but the opposite could also be said: that the engineers (with a royal We) probably missed out on learning some business acumen, or some practical trade.
One thing I like about the format here, and the hobby in general, is that it's so accessible: you can buy low-cost equipment and start doing real scientific experiments today. And many of the things that are commonly accepted as 'fact' are really just theories, or approximations, or guesswork, or convenient models but not necessarily 100% accurate. Take the 'structure' of the atmosphere, for instance. Is it really made of a springy 'cloud' of atomic particles, bouncing around like tiny billiard balls? That is by no means certain. Only by doing various things to the air and by careful observation, can we discover its true properties.
One thing I like about the format here, and the hobby in general, is that it's so accessible: you can buy low-cost equipment and start doing real scientific experiments today. And many of the things that are commonly accepted as 'fact' are really just theories, or approximations, or guesswork, or convenient models but not necessarily 100% accurate. Take the 'structure' of the atmosphere, for instance. Is it really made of a springy 'cloud' of atomic particles, bouncing around like tiny billiard balls? That is by no means certain. Only by doing various things to the air and by careful observation, can we discover its true properties.
abstract,
Thank you for your post that I liked and I agree with everything you wrote and that I've said many times even if in other form and in other circumstances.
I also agree with the fact of experimenting and questioning what one thinks to know, but when two or more members follow the thread of a discourse they have necessarily to adopt the same syntax and a common base of knowledge, otherwise communication may easily fail.
About engineers and the presumed greater "mental freedom" of those who are not, I've written many times that it is precisely the commitment and sacrifice of having studied a subject having spent many years and a lot of money of one's life that for some represents a "mental cage" that may to limit their horizons rather than broadening them.
I didn't say it happens to everyone and all the time, I just said I've seen it happen more than once.
Of course, I myself sometimes considered some threads a bit excessive because it seemed that the various commentators were comparing themselves on a dilemma without finding a solution, but then they always fascinated me and I continued to read them, or I simply stopped doing it...
Speaking of the experiment, I thank you for mentioning it because I was sincerely surprised by the fact that only one (authoritative) member did it reporting the expected result, followed then only by (equally authoritative) @Jeffh01.
It seems to me that you have not done it either, even though it is not a challenging experiment at all, and I still do not understand the real reason, except for the fact that it's obvious that if the topic doesn't interest you, you won't even do a simple experiment.
If it were me, and my immense curiosity, I could not have resisted doing it and posting here the results. 😉
Thank you for your post that I liked and I agree with everything you wrote and that I've said many times even if in other form and in other circumstances.
I also agree with the fact of experimenting and questioning what one thinks to know, but when two or more members follow the thread of a discourse they have necessarily to adopt the same syntax and a common base of knowledge, otherwise communication may easily fail.
About engineers and the presumed greater "mental freedom" of those who are not, I've written many times that it is precisely the commitment and sacrifice of having studied a subject having spent many years and a lot of money of one's life that for some represents a "mental cage" that may to limit their horizons rather than broadening them.
I didn't say it happens to everyone and all the time, I just said I've seen it happen more than once.
Of course, I myself sometimes considered some threads a bit excessive because it seemed that the various commentators were comparing themselves on a dilemma without finding a solution, but then they always fascinated me and I continued to read them, or I simply stopped doing it...
Speaking of the experiment, I thank you for mentioning it because I was sincerely surprised by the fact that only one (authoritative) member did it reporting the expected result, followed then only by (equally authoritative) @Jeffh01.
It seems to me that you have not done it either, even though it is not a challenging experiment at all, and I still do not understand the real reason, except for the fact that it's obvious that if the topic doesn't interest you, you won't even do a simple experiment.
If it were me, and my immense curiosity, I could not have resisted doing it and posting here the results. 😉
Last edited:
Jeff, thank you!
I was regarding vibration and movement as synonyms since vibration is just a special case of movement, namely movement about a central position.
If we align on our terminology (and that would no doubt be helpful!) it would be be true to say that both the tissue paper and the silicone rubber exercise band vibrated very vigorously. There was some residual mvement at the end of the experiment as the materials returned to their rest position. This was artifact of imperfect alignment and not something to be unduly concerned about.
I would note that the spl I used for the experiment was probably over 100db, much louder than normal domestic listening.
You are completely correct, and this agrees with my results, that sound propagates the same way regardless of frequency and amplitude.
What I demonstrate is that at low frequency (25Hz in my case) and high amplitude you can see the sound wave being launched from the drive unit by placing thin material orthogonal to the direction of the wave.
This isn’t a hard experiment to do if you have a tool like REW or WinSpeakers, and especially if you have tone controls that allow you to boost the bass so that bass cone movement is much higher than normal.
At the volume I used for testing I wouldn’t want any glassware in the vicinity though!
I am hoping that this makes a bit more sense now. 🙂
Let me know if it doesn’t!
Yours is a great post for me! 👍
And I don't want to add anything else now...
Abstract,
You compared 100:101 to 100:99, Correct, the ratios are not exactly equal.
Both ratios are just like 2nd harmonic distortion, long in one direction, and short in the other direction.
Speakers do have 2nd harmonic distortion at some level or another level. It is Unidirectionay non-linear, it is not Bidirectionally nonlinear.
Bidirectional nonlinear is 3rd harmonic distortion (and speakers have 3rd harmonic distortion, at some level, or at some other level).
If the signal dictates 100:100, but we only get 99:99, that is Bidirectionally non-linear, both directions are short, 3rd harmonic distortion.
Consier the linear signal to be 1:1, 2:2, 3:3, . . . . 98:98, 99:99, and then when it should be 100:100 we only get 99:99 for the second time again (clipped response; non-linear, but equally in both directions).
A very poor example of air molecules bouncing into each other is attached.
You compared 100:101 to 100:99, Correct, the ratios are not exactly equal.
Both ratios are just like 2nd harmonic distortion, long in one direction, and short in the other direction.
Speakers do have 2nd harmonic distortion at some level or another level. It is Unidirectionay non-linear, it is not Bidirectionally nonlinear.
Bidirectional nonlinear is 3rd harmonic distortion (and speakers have 3rd harmonic distortion, at some level, or at some other level).
If the signal dictates 100:100, but we only get 99:99, that is Bidirectionally non-linear, both directions are short, 3rd harmonic distortion.
Consier the linear signal to be 1:1, 2:2, 3:3, . . . . 98:98, 99:99, and then when it should be 100:100 we only get 99:99 for the second time again (clipped response; non-linear, but equally in both directions).
A very poor example of air molecules bouncing into each other is attached.
Attachments
Last edited:
Yes, they are not synonymous, and I like enough your definition although for the sake of accuracy I still prefer the one I wrote about two years ago on another thread.
I still prefer the above definition because it describes a vibration as an oscillation and not as a movement.
This way it prevents both any possible ambiguity and misunderstanding. 😉
That's exactly how it is, and I perfectly agree that the way in communication should be standardized. 👍
🙂