Chris, it is in the book. Buy a copy and read it. You'll probably learn something new... or at least a different view of what you already know.
dave
According to Amazon.ca the first edition is $163.00
. The new one is only $22.50 (less than in the states) but it's out of stock. I put in an order anyway, as they tend to take the sale prices away after restocking.
Hi Dave,
No, not to clear up the simple points I have raised. Especially not since I can see what I would consider to be incorrect assumptions posted and on his web site. It's Esa's book and Esa's comments. Like statements made anywhere else, the author should be able to explain the basis for the conclusions drawn without forcing people to buy the book in order to understand where the author is coming from. In fact, since there is no two way dialog going on in reading a book, sooner or later the concepts need to be discussed somewhere.
To be honest, clearing up a couple points I've raised will not endanger his book sales. In fact, touching on a couple points will raise curiosity and probably increase book sales. I have a decent library of books already, so I'm not adverse to paying for something that I will benefit from. If you saw my place, you'd understand this (then run screaming! ). My concerns rest with some things I have read that contradict what I have seen in my own experiments, they need to be clarified before I'll part with any $$. This is especially true when money is in short supply for me right now, I'm sure you'd agree if faced with the same situation yourself.
If you feel that you can answer some of my concerns / questions, I'd be happy to exchange email with you on this. I'd like to see your perspective on this.
Then we also have a new approach being used with sub-woofers like the Sunfire and others. They are treating the woofer as a piston only, with little regard for what T/S parameters indicate. I don't agree with the practice, but I guess if you throw enough power at a problem, it will go away.
Best, Chris
No, not to clear up the simple points I have raised. Especially not since I can see what I would consider to be incorrect assumptions posted and on his web site. It's Esa's book and Esa's comments. Like statements made anywhere else, the author should be able to explain the basis for the conclusions drawn without forcing people to buy the book in order to understand where the author is coming from. In fact, since there is no two way dialog going on in reading a book, sooner or later the concepts need to be discussed somewhere.
To be honest, clearing up a couple points I've raised will not endanger his book sales. In fact, touching on a couple points will raise curiosity and probably increase book sales. I have a decent library of books already, so I'm not adverse to paying for something that I will benefit from. If you saw my place, you'd understand this (then run screaming!
). My concerns rest with some things I have read that contradict what I have seen in my own experiments, they need to be clarified before I'll part with any $$. This is especially true when money is in short supply for me right now, I'm sure you'd agree if faced with the same situation yourself.If you feel that you can answer some of my concerns / questions, I'd be happy to exchange email with you on this. I'd like to see your perspective on this.
Then we also have a new approach being used with sub-woofers like the Sunfire and others. They are treating the woofer as a piston only, with little regard for what T/S parameters indicate. I don't agree with the practice, but I guess if you throw enough power at a problem, it will go away.
Best, Chris
A coil moving through a magnetic field is anyway a voltage source according to the formula e = Blv. It produces current only if there exists a current path, the current being then Blv/Z, where Z is the impedance of the path.keantoken said:
What have you realized? Is this not a commercial area? What rule is being violated?anatech said:
Chris,
Perhaps you really are somewhat open minded about these issues, as you say, but some of your commentary in its irrelevancy quite doesn't support this assumption.
Anyway, your point seems to be in essence that the common practice must be the best practice because it is the common practice. I don't think that way, and I understand the message can appear quite tough for those who do.
anatech said:
anatech said:
No, absolutely not. When a coil moves in a magnetic field it generates an EMF according to the formula EMF=Blv which defines a voltage source. This EMF voltage is generated irrespective of how the coil ends are connected. Current is generated only if there is a path for that current, i.e. if the coil is connected to some finite impedance. In a voltage driven system, the coil is connected to zero impedance, so the EMF-derived current is limited mainly only by the voice coil's resistance. In a current driven system, the coil sees, in principle, infinite impedance, so the EMF is not able to generate any current.anatech said:
As for the damping, it is indeed only a matter of shaping the frequency response at the low end. When this is done by whatever means, the speaker is damped, and there is no further need to "arrest" anything.
As I said in post 10, the frequency response and transient response of any linear system are not separate things but one and the same thing only viewed in different ways. If any two linear systems have the same frequency response (amplitude & phase), then their transient responses (for any input) must also be equal - there cannot be any difference. This stems directly from the Fourier Transform and properties of linear systems. Therefore, if the frequency response of a loudspeaker that is designed for current operation is made equal to the frequency response of a loudspeaker designed for voltage operation, then all the transient properties of the two speakers are also automatically equal, and in this respect one cannot be better than other.
If you are still left with open concerns, please state them clearly one or two at a time, and I'll be happy to address them as soon as I can.
Hi SY,
I'll read the paper once I have a chance. I generally do look forward to reading material that agrees with basic physics.
Hi Esa,
Explain a moving thread? I had zero to do with that. I didn't even know it was moved to begin with.
I'm going to keep my comments simple for members who may not have studied electrical circuits. Don't assume I'm talking down to you.
As for the laws of physics concerning conductors cutting across magnetic lines of force are concerned, I'm pretty sure I understand that basic principle. Everything I have been taught on this subject or learned later in life has centered on the induced current. Now, may I ask if you are considering transformer action, or motor action that uses a permanent magnet? I'm wondering if there is confusion caused by a different viewpoint. As I mentioned, your definition is one I haven't seen before as applied to a motor or generator. It may be correct as far as I know, or it may be applied incorrectly as well. However, the approach taken by what I am about to say holds for all normal situations. An open circuit is not a useful configuration for a loudspeaker (piezoelectric and any other exotic types exempted).
In a generator, when a conductor is passed through an electric field, a current is induced in that conductor that depends on how strong that field is, and how quickly the "lines of force" are cut, or transversed. The important point to understand is that it is the amount of current that can be calculated, the induced voltage depends on the impedance of the circuit that the conductor is part of. The voltage that results from this current flow has been considered a secondary effect resulting from the induced current. When considering normal transformers, we tend to think in terms of induced voltage because we are concerned with turns ratios between the primary winding and a secondary winding. We apply the current levels in order to figure out IR losses and core heating in that situation.
A loudspeaker is a motor, or a generator in reverse. We would normally think in terms of the strength of the magnet structure that creates a certain level of magnetic flux in the voice coil gap. The voice coil itself consists of "x" number of turns or wire (conductor) that will be moving within the magnetic field. From this we can calculate the amount of motional force generated per turn of wire per unit of current. This is first principles of course, we don't consider the number of windings that may be outside the field. If you then add up the number of windings (contained in the field at any moment if you want to be more precise) and multiply that by the current and whatever constants you want to use, the amount of actual force generated will be roughly known. You can get an exact figure of force if you include things like how much of the coil is not within the magnetic field and whatever other losses you want to throw in. The important thing is that the amount of voltage you need to apply to create that current will depend on the inductance (variable to some extent) and temperature (affects the resistance of the wire and magnet strength) and of course, the applied frequency. I am assuming that you are not applying a DC current, but you could figure that out as well if needed.
Now, we agree in that the dynamic loudspeaker is operated by the levels of current in it's windings. Is that your point? If so, no complaints from me.
Please allow me to counter. Just because you have an approach that is more recent than the accepted viewpoint does not mean the current ideas are incorrect. In fact, the onus is on you to either disprove the current, accepted understanding, or to qualify how your new information is applied in order to co-exist with the current understanding.
Common practices exist because the underlying science has been vetted by other practitioners of the art. Fair? These people who did come before you were not stupid people, so it would be wise to consider your information very carefully before discarding what is generally accepted in the field. Common practices tend to be refined to be modified over time to accurately reflect the current understanding of the subject, much like a living document. Can you accept this? Note that I didn't claim anywhere that I am right and you are wrong. In fact, my structured education occurred in and around 1980, with many years working in this area designing speaker systems and diagnosing failures. It is possible that what you are saying here is the same thing I am, only from a different viewpoint.
Also, the term "arrest" and "damping" refer to the same thing as far as the speaker is concerned. To apply damping to the driver will arrest the motion of said driver. Let's try not to split hairs in definitions unless you really didn't understand the intent.
The normal way to design a dynamic loudspeaker normally involves effort to create a flat response in terms of voltage drive, not in current drive. The end result is a product that will closely follow it's impedance curve if you do drive it from a current source rather than a voltage source. No problems so far, right? This being the case, I'm afraid that the status quo applies as far as I can see. To be successful, the dynamic loudspeaker must be designed from the ground up aimed at current drive. Playing with reactive components to adapt a driver to work in the other type of system will probably reduce the system efficiency quite a bit.
I have not read the papers yet, but I will. Please feel free to comment on a couple questions at a time. We may very well be dancing around the same bush here, each of us seeing one side. I'd be interested to see how much we can agree on that is separated by terminology.
-Chris
I'll read the paper once I have a chance. I generally do look forward to reading material that agrees with basic physics.
Hi Esa,
Explain a moving thread? I had zero to do with that. I didn't even know it was moved to begin with.
I honestly thought I was clear in my response to Bear. I understand more clearly that you are promoting your book (a product). That is all, no more and no less. I'll add a comment now. If I know that your book is factual and correct, I'll have no problems reading it or recommending it to others. At the moment, I am uncomfortable with things I see as opposing the reality as I understand it. Again, no more and no less. I am grateful that you are discussing the general theory so that I may learn something about it.
I'm going to keep my comments simple for members who may not have studied electrical circuits. Don't assume I'm talking down to you.
I try to be open minded, I really do. The only thing I don't understand about what you have said here really applies to the fact that I'm trying to fit what you are saying in with what I know. We seem to disagree on some points, that's all.
I can't agree with you here. That isn't what I was taught (less than 50 years ago!).
As for the laws of physics concerning conductors cutting across magnetic lines of force are concerned, I'm pretty sure I understand that basic principle. Everything I have been taught on this subject or learned later in life has centered on the induced current. Now, may I ask if you are considering transformer action, or motor action that uses a permanent magnet? I'm wondering if there is confusion caused by a different viewpoint. As I mentioned, your definition is one I haven't seen before as applied to a motor or generator. It may be correct as far as I know, or it may be applied incorrectly as well. However, the approach taken by what I am about to say holds for all normal situations. An open circuit is not a useful configuration for a loudspeaker (piezoelectric and any other exotic types exempted).
In a generator, when a conductor is passed through an electric field, a current is induced in that conductor that depends on how strong that field is, and how quickly the "lines of force" are cut, or transversed. The important point to understand is that it is the amount of current that can be calculated, the induced voltage depends on the impedance of the circuit that the conductor is part of. The voltage that results from this current flow has been considered a secondary effect resulting from the induced current. When considering normal transformers, we tend to think in terms of induced voltage because we are concerned with turns ratios between the primary winding and a secondary winding. We apply the current levels in order to figure out IR losses and core heating in that situation.
A loudspeaker is a motor, or a generator in reverse. We would normally think in terms of the strength of the magnet structure that creates a certain level of magnetic flux in the voice coil gap. The voice coil itself consists of "x" number of turns or wire (conductor) that will be moving within the magnetic field. From this we can calculate the amount of motional force generated per turn of wire per unit of current. This is first principles of course, we don't consider the number of windings that may be outside the field. If you then add up the number of windings (contained in the field at any moment if you want to be more precise) and multiply that by the current and whatever constants you want to use, the amount of actual force generated will be roughly known. You can get an exact figure of force if you include things like how much of the coil is not within the magnetic field and whatever other losses you want to throw in. The important thing is that the amount of voltage you need to apply to create that current will depend on the inductance (variable to some extent) and temperature (affects the resistance of the wire and magnet strength) and of course, the applied frequency. I am assuming that you are not applying a DC current, but you could figure that out as well if needed.
Now, we agree in that the dynamic loudspeaker is operated by the levels of current in it's windings. Is that your point? If so, no complaints from me.
Okay, you're talking in a circle here. I think I get the gist of what you are saying though.
Please allow me to counter. Just because you have an approach that is more recent than the accepted viewpoint does not mean the current ideas are incorrect. In fact, the onus is on you to either disprove the current, accepted understanding, or to qualify how your new information is applied in order to co-exist with the current understanding.
Common practices exist because the underlying science has been vetted by other practitioners of the art. Fair? These people who did come before you were not stupid people, so it would be wise to consider your information very carefully before discarding what is generally accepted in the field. Common practices tend to be refined to be modified over time to accurately reflect the current understanding of the subject, much like a living document. Can you accept this? Note that I didn't claim anywhere that I am right and you are wrong. In fact, my structured education occurred in and around 1980, with many years working in this area designing speaker systems and diagnosing failures. It is possible that what you are saying here is the same thing I am, only from a different viewpoint.
Well, close enough. In fact, near the crossover points the crossover exhibits an impedance comparable to that of the driver. The crossover element acts as an energy dissipating element that raises the impedance of that circuit in order to restrict current flow through that leg of the circuit. The fact that these components are reactive just adds to the fun. So I have to say that your comment is correct depending on the applied frequency, or if the driver in question is driven directly.
Sorry, but we are miles apart here. I completely and strongly disagree with this comment. I think I understand what you are saying here, but I'm having trouble accepting that the energy that is created due to motion in the voice coil w.r.t. the magnetic field doesn't show up anywhere. This energy must be accounted for in some way. Now, if you are saying that the energy has only a minor effect and can be ignored, that I may accept.
Well, there is a need to control the movement of the cone or diaphragm. If this is not done, you will have a transducer that vibrates in an uncontrolled manner. Therefore, there must be a system or method in place that will oppose uncontrolled movement. Whether you decide to short the "motor" out so that it's own motion creates the controlling force, or you actively apply the energy required is up to you. No matter how you do this, energy must be dissipated in some way to control the radiating surface. Passive elements placed in parallel with the driver may or may not properly do the job. Convince me, please.
Also, the term "arrest" and "damping" refer to the same thing as far as the speaker is concerned. To apply damping to the driver will arrest the motion of said driver. Let's try not to split hairs in definitions unless you really didn't understand the intent.
See? This is where I think you are playing with words. What process or method do you expect to use that will "shape the frequency response"?
The devil is in the details, the real world things where minor factors for one approach may be major issues in another approach. Controlling transients in a dynamic loudspeaker is not a trivial matter, as you know. Highly detailed frequency response curves that include detailed phase information are a part of the picture. A series of curves, called a "waterfall" will reveal the rest of the information needed to fully appreciate what the driver is doing. What the public sees are averaged curves that have been smoothed a little further. There are several reasons for this, and I only mention it to counter your statement that suggests the conversion between a current drive and voltage drive system is that straight forward. Maybe in theory, but it has to work in the real world.
The normal way to design a dynamic loudspeaker normally involves effort to create a flat response in terms of voltage drive, not in current drive. The end result is a product that will closely follow it's impedance curve if you do drive it from a current source rather than a voltage source. No problems so far, right? This being the case, I'm afraid that the status quo applies as far as I can see. To be successful, the dynamic loudspeaker must be designed from the ground up aimed at current drive. Playing with reactive components to adapt a driver to work in the other type of system will probably reduce the system efficiency quite a bit.
I have not read the papers yet, but I will. Please feel free to comment on a couple questions at a time. We may very well be dancing around the same bush here, each of us seeing one side. I'd be interested to see how much we can agree on that is separated by terminology.
-Chris
maxro said:
I don't undrestand why it shows out of stock, but I doubt there may be some confusion with the old version. As you have an account on Amazon.ca, are you able to inquire this?
Though the basic themes are related, in no way is the book based on the M&H article. The table of contents is here for anyone to see this. Also, how could an about 18 page paper serve as a substitute for a 340 page book?SY said:
"Well-known stuff"? The essentials of current-drive are everything but well known. The general public has never been given any chance to try and experience it, no commercial systems have ever been manufactured, and even the audiophiles have hardly heard about it; and those who have are misguided and unaware of the fatal flaws of voltage drive.
Mills & Hawksford did actually some disservice to the concept by discarding the basic current feedback scheme by unfounded justifications in order to promote their own extremely complex amplification system that has no real advantages and is not likely to rise interest. They also didn't address much the actual flaws of voltage drive and thus quite didn't see the big picture.
Hi Esa,
My concerns originate in what I see as statements made without explanation or proof. There may well be some exaggerations made on your part, this is see from your posts and a little in the choices in subject headings. It appears that you may be attacking the current state of the art rather than taking a more balanced and factual view. For example, "Microphone Effects". Yes, a loudspeaker can and does act as a microphone. But what is the magnitude of this effect, and how much impact does it have on a real system in the real world? It is completely possible (and common practice) to focus on a perceived problem and blow it up out of proportion in order to sell an idea or product. Are you assigning the real level of importance to these problems, or are they simply a tool or gimmick? I'm not trying to upset you, but I am voicing what my concerns are to you.
The real problem is with the advertising in the audio field. Most advertisements are inaccurate and technically wrong. The public is fed up with this and just given up. So, while you could get your message out that your system is better (from your standpoint) because of it's operating method, the details will be twisted in such a way so that all the information will simply be regarded as noise by the public.
Major factor here, the very limited pool of speakers and amplifiers to choose from. In fact, you would be further ahead to package the system in the speaker boxes and sell and active system. Otherwise, I can't see the public taking a risk on a new system.
Esa, it seems to me that if you wish to get this information out into the world, some explanation might really help your cause. This seems to be your major complaint - the operation of a current drive system is partially unknown and also not well understood. I am trying to give you the opportunity to correct this. You have an audience, all you have to do is type now.
-Chris
Since their paper came before your book ... They wrote a paper detailing their findings. It was not intended as a substitute for anything. SY has asked what I think is a reasonable question. It should be easy to answer. Want to give it a whirl? The table of contents doesn't actually say much.
My concerns originate in what I see as statements made without explanation or proof. There may well be some exaggerations made on your part, this is see from your posts and a little in the choices in subject headings. It appears that you may be attacking the current state of the art rather than taking a more balanced and factual view. For example, "Microphone Effects". Yes, a loudspeaker can and does act as a microphone. But what is the magnitude of this effect, and how much impact does it have on a real system in the real world? It is completely possible (and common practice) to focus on a perceived problem and blow it up out of proportion in order to sell an idea or product. Are you assigning the real level of importance to these problems, or are they simply a tool or gimmick? I'm not trying to upset you, but I am voicing what my concerns are to you.
The general public does not understand the technical details, nor do they care. They don't know or care why the current systems are the way they are. They continue to merrily blow stuff up.
The real problem is with the advertising in the audio field. Most advertisements are inaccurate and technically wrong. The public is fed up with this and just given up. So, while you could get your message out that your system is better (from your standpoint) because of it's operating method, the details will be twisted in such a way so that all the information will simply be regarded as noise by the public.
Major factor here, the very limited pool of speakers and amplifiers to choose from. In fact, you would be further ahead to package the system in the speaker boxes and sell and active system. Otherwise, I can't see the public taking a risk on a new system.
No system is perfect in execution. The issues faced with voltage drive are known, but I can't agree that they are fatal flaws. Current drive is a valid approach, but then again, so is voltage drive. So which is better as a physical system? I don't know, but I am willing to accept that your approach solves problems experienced with voltage drive. Who knows what issues a current drive system may face?
I am reading those papers now. They have a view point and so do you. Can you elaborate on what you believe to be the correct point of view? This is what I have been trying to have you do, address the issues as you see them and explain what you have found.
This is a strong statement you've made here, and to claim they didn't understand the subject might be going a little too far. Remember that they may hold the same opinion on your own work. All you have really said that can be backed up is that you don't agree with their paper and conclusions.
Esa, it seems to me that if you wish to get this information out into the world, some explanation might really help your cause. This seems to be your major complaint - the operation of a current drive system is partially unknown and also not well understood. I am trying to give you the opportunity to correct this. You have an audience, all you have to do is type now.
-Chris
Chris,
BackEMF is something that those i learned from have hammered on since i started some 35 years ago. It is certainly of large enuff magnitude to affect downward dynamic range.
And if it gets into the feedback loop of your amplifier it has the potential to cause all sorts of havoc.
dave
What kind of distortion measure is actually going to tell us anything useful as far as sonics are concerned?
Just buy the book and read it, and then you can do a review. It has all sorts of interesting measured results in it.
If you want to have a discussion on the merits and drawbacks of current drive, it might be best in the main forums.
dave
I don't think it fair to say that either one of these systems is "right", and the other "wrong".
To quote Peter Walker: "The horse and the motor car are both effective forms of transport, but the car is not very good at jumping a five-barred gate, nor is it seen at it's best in a ploughed field."
btw, the table of contents looks promising, suggesting a much wider variety of topics than was covered by Mills and Hawksford.
The appendixes look like a nice touch too, for those of us who may be a bit rusty (or didn't pay enough attention in class to start with).
Let's see if the book's available around here...
To quote Peter Walker: "The horse and the motor car are both effective forms of transport, but the car is not very good at jumping a five-barred gate, nor is it seen at it's best in a ploughed field."
btw, the table of contents looks promising, suggesting a much wider variety of topics than was covered by Mills and Hawksford.
The appendixes look like a nice touch too, for those of us who may be a bit rusty (or didn't pay enough attention in class to start with).
Let's see if the book's available around here...
Evidence? Seems to me that any reasonably well-designed amp (the vast majority of non-exotic ones) handle back EMF just fine, as can be seen with measurements using a loudspeaker load or RLC equivalent load. Moreover, a current drive amp will not suppress back EMF at all- nor should it, in a proper system design. And a current drive amp will generally have a feedback network as well...
To be honest, I'm quite put off by the author's approach- not the technical one, the literature does show the merits of current drive as part of an overall system design- but the attitude of, "pay no attention to all of the other systems used successfully in millions of installations over 75 years, it's all wrong, I have the Only Way." I don't see anything in the table of contents which would lead me to believe that there's anything beyond expansion of well-known principles which abound in the primary literature. Not that simple, expanded explanations for non-engineers is a bad thing, but I'm skeptical that there's anything new here, beyond evangelical attitude.
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