The heating of the coil is a separate process to that of exchanging energy between electrical and mechanical forms by moving an electrical current within a magnetic field. The latter is usually modelled as 100% efficient with no losses.
If you want to consider the efficiency of a system then you must define what is contained within that system in addition to the "electrical-to-mechanical energy conversion". This will place some processes within the system with energy changing form but not being lost and place some processes on the boundary of the system. The sum of the energy exchange with the outside of system will be zero but one usually needs to introduce some extra information about what is going on at the boundary (boundary conditions) in order to fully determine what is going within the system.
Formulating the problem/question is often the lengthy part if something is new. Working out what you don't know when you don't know it is not straightforward and is a skill that professional researchers take significant time and effort to acquire. The templating, learning-by-rote, soundbites, bombarding by huge amounts of incomplete slanted marketing information, narrower bubble of information we inhabit, etc... of the modern world is having the practical effect of leading to less-and-less people mastering it. This seems crazy initially given the relevant information is undeniably a lot easier to access these days. The problem is what is also present which is a vast amount more information that is irrelevant, misleading or worst slight misleading to serve an interest other than ones own. End of rant.
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So what is the efficienty including the heating of the coil? I.e. from "voltage*current" at the input terminal of the driver to the mechanical motion of the cone itself in a vacuum? How much higher is that compared to the total efficiency for the acoustic radiation?
Come on, let's define the mechanic motion as a useful work then. For whatever purpose. You are trying to teach me to ask the right questions and now you back away? 😀😉
Which part? The kinetic energy of the motion? The potential energy stored in the suspension? The heating of the suspension due to damping?
By failing to formulate a system in order to pose a sensible question you are getting a series of silly answers to silly questions.
The script to produce the acoustic efficiency plot earlier including all the physics for the driver is about 100 lines long. Here is the heart of it (which needs checking due to haste on my part):
Zr = rfac*radimp(2*ka)
Zc = complex(Rc, w*mc - sc/w)
ZE = complex(RE, w*LE)
Zm = Zr + Zc
ZM = phi2/Zm
ZI = ZE + ZM
ae = phi2*Zr.real / (phi2*(Zr.real + Rc) + RE*(abs(Zm*Zm)))
I would suggest writing a script like this guided by an acoustics text book is likely to teach you more about what you want to know and in a shorter time compared to asking vague questions on a forum like this over a period of days.
OK. Well, the physics is obviously not my expertise nor profession so I don't really have the urge to purse this further. I was just baffled and curious so I asked and hoped that someone may know in layman's terms. Thanks for your time again and sorry for bothering you.
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If you were bothering me I would have stopped reading the thread and certainly wouldn't have contributed. I am interested in why questions like yours struggle and why technical competence is falling rather than rising given the explosion in easily accessible information sources. It is related to a possible project I have been pondering on the engineering/science of DIY speakers.
You have to be well educated to understand. The explosion in easily accessible information sources causes that you can read a lot about a lot if things, but the education is still missing at the core of it - I guess only a very few people will be able to learn something completely new to them just be reading books. Information available doesn't make the proper education (and understanding), which is interactive.
BTW: YouTube
(I don't have a clue why two magnets repel each other, but I love the video.)
BTW: YouTube
(I don't have a clue why two magnets repel each other, but I love the video.)
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I abandoned trying to get technical information from videos many years ago because it is an inefficient and irritating source. Effective learning requires thought and effort not simply allowing information to passively to wash over you. Some bits can be skipped, some need to be reread, some need detours to check some background, etc... It is an active process not a passive one.
That´s an important problem and has been happening for decades.
As I see it, just chatting theory around a (virtual) coffee/beer table leads to indecisive results, because "everybody has his own opinion" and discussions can go on forever.
This very thread is an example: 73 answers and it has NOT been settled (or at least agreed upon) yet ... while the original question was quite straightforward and was answered (from my point of view) within the first 4 or 5 answers. 😎
While Engineers actually manufacturing products don´t have such a luxury, product must be made, at an economic price, in large quantities, it must reasonably meet expectations and most important: go through the output door NOW to be shipped to Customers.
In my view, that´s why Japanese Engineers first, then Koreans, today Chinese and Indians became or are becoming the Technology reference, where advances are made, while us in America or Europe are being left behind and reduced to what I mentioned above: Forum discussions, with very few distinguished exceptions.
Theory is fine and necessary, but the ultimate test is its practical application.
US/Europe led the World in the old days, when Western Electric, RCA, Texas Instruments, Honeywell, Siemens, ITT, Telefunken, Philips, etc. were actually producing World´s Hi Tech stuff.
When such manufacturing was transferred to the Far East on quick profit grounds, slowly but surely Technical savvyness followed it.
Talk about killing the golden goose!!!! 😡
EDIT:
That.
That too.
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Why are you taking it so seriously? For me this is just an occasional fun. It's completely irrelevant to what I really do, there's no obligation and no consequence.
- So on a more funny note, do you understand that we will all die? 😀
You are not sure? 🙂
- So on a more funny note, do you understand that we will all die? 😀
You are not sure? 🙂
I don't know if it was said before or not since I did not read the whole thread.
Kinetic Energy and Potential Energy do not do work and so they do not dissipate energy. They are called conserved quantities since they conserve energy. Reactive components never dissipate energy it is only dissipated in the nonconserved parts, namely the resistance. In your example the resistances must not be changing so for a given voltage the energy loss is the same just as the radiated power is the same. Changing the reactive components don't affect this.
But also keep in mind that your simple example is only true well above resonance and remember that the resonance will certainly change as will the Q's of the resonance.
My main point here is that reactive components like mass and compliance do not dissipate energy.
Kinetic Energy and Potential Energy do not do work and so they do not dissipate energy. They are called conserved quantities since they conserve energy. Reactive components never dissipate energy it is only dissipated in the nonconserved parts, namely the resistance. In your example the resistances must not be changing so for a given voltage the energy loss is the same just as the radiated power is the same. Changing the reactive components don't affect this.
But also keep in mind that your simple example is only true well above resonance and remember that the resonance will certainly change as will the Q's of the resonance.
My main point here is that reactive components like mass and compliance do not dissipate energy.
I'm definitely going to re-read the beginning chapters of Audio Transducers, as I still have the paper copy from you, I guess it's all there (the T-Matrices). Originally I just quickly skimmed through to the Chapter 6...
Exact same thing. Just do the energy balance. It's straight forward as long as you assume operation is in the mass dominated region, well above the drivers resonance. All work done is stored in the mass element. Move around resonance and you have to consider damping and compliance so not the same as you have to consider losses and energy storage in the compliance elements. And well below resonance, compliance is all that matters.
Mass dominated, Assume F = sin(wt)
F = M x a = m x dv/dt
v = Int (F x dt)/m = Int(2F x dt)/ 2m
Velocity of both masses is the same.
KE = m v^2/2 Double m, double KE.
Compliance dominated region,
F = k x X
dF/dt = k x dx/dt = k x v
v = dF/dt / k
for driver of mass m, force F.
v = 2dF/dt / k
for the driver with mass 2m and force 2F.
KE = m v^2/2
Driver of mass, m
KE = m v^2/2
Driver of mass 2m
KE = 2m (2v)^2/2 = 8 m v^2/2
So in the compliance dominated region the max KE of the 2m cone will be 8 times that of the 1m cone.
The driver with double force will also have twice the excursion.
Since for both drivers the velocity will vary sinusoidally when subjected to F = sin(wt) the KE of both drivers will vary between zero at max excursion (v=0) to a maximum where cone passes through the point of zero displacement.
Except that it was not... Post #2 is inaccurate as the electrical to mechanical transducer is actually quite efficient! That "useless work" is not work in the physical sense. It might be conceived as instantaneous infinitesimal work (of which there is more, yes), but this is only relevant in the case of an instantaneous impulse. In the steady state analysis, the mechanical load is almost entirely reactive and the mechanical work essentially vanishes. In this state, idealized mechanical components consumes NO energy at all!
Post #4 is just wrong. There certainly is energy in a magnetic field, however the energy in the field of the magnet is fixed and uncoupled to the system of interest. The energy in the magnetic field produced by the coil is not fixed and creates a purely reactive impedance presented to the current in the coil. This is called inductance. Again, no net energy is dissipated in the steady state.
Post #5 misses the point as yes, there might be larger mechanical forces applied on the enclosure, but if this enclosure is stiff enough, these forces cannot do any work (work is forces times distance). In any case, any work they might do will mostly end up exciting resonant modes in the enclosure which will, again, appear as a reactive load. The minor dissipation that vibration of the enclosure might entail has nothing to do with the OP's question.
Posts #3 is actually the closest to the answer, pointing in the right direction and asking the right questions. Admittedly, it is rather short for an answer...
I agree with some of the ideas in the rant that followed. However, theory, at the level of those linear systems is well understood and the answer is pretty obvious to me as this is a physics question (I'm a mathematical physicist), although I might not explain myself effectively. The problem is not that "chatting theory" is uneffective, but rather that this discussion involves people learning how to apply that theory (which is entirely fine, but will necessarily lead to "indecisive results"). Do not confuse a DIY board where people are learning to a production or professional environment. Chinese or not.
I side with mabat on the issue you raised as there is a wealth of information but most people cannot properly consume it. Although I disagree with the comment on books as, to me, it is the best format to learn, but as Andy19191, this is not like reading a novel, it is an active and sometimes tedious process.
That is because the CONVERSION from electrical to mechanical is nearly 100% efficient, however once the energy gets in the mechanical system it is presented with an (to first order) entirely reactive load and is thus entirely reflected, converted again from mechanical to electrical and then either absorbed in the power supply or reflected, yet again towards the driver, on and on. In the steady state, all those reflections are happening at the same time and one has standing waves. The current standing wave in the coil resistance is where the energy gets dissipated (neglecting all other dissipative phenomenon).
It's not the conversion that is inefficient, it is rather that the energy has nowhere to go in the mechanical system and ends up going back in the electrical system. That is what Andy19191 was alluding to with "no work is done [...] efficiency is zero".
You must be joking.
You seriously call a 1% efficient transducer (on a good day) EFFICIENT? 😱
You call a machine which moves , say, 35 grams of cone + voice coil bobbin + former + spider + dome + adhesives just to push/pull, say, 2 grams of air (which is what we actually hear) ... EFFICIENT?. 😕
I said that the electrical to mechanical transducer is quite efficient. You are talking about the mechanical to acoustical transformation which is indeed quite inefficient, to the point that it can be entirely neglected on a first pass. The fact that the mechanical transducer is heavy does not inherently make it inefficient. However, it does give it a significantly higher impedance than air, hence the inefficiency to make sound, not motion.
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