Yeah, you could be right, as I said I'm not sure. I'll wait for the book.
OTOH suppose this is indeed a better solution, it begs the question why all those 1000's of engineers never got it.
But it is possible; we have a similar situation with opamps - they are all voltage amplifiers (even the CFB ones are used that way) while many people hold that a true current amplifier would have given us much better opamps.
We'll see.
jd
I guess speakers could be modelled with a nonlinear impedance, hence the said better harmonic distortion performance with current drive.
Unfortunatly Esa didn't publish distortion measurements himself.
regards
Unfortunatly Esa didn't publish distortion measurements himself.
regards
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Hi,
Hear, hear.
Absolutely right.
Well, there are several secondary terms in the equations, however I'd say that in the frequency range where the diaphragm movement of the driver is small it holds well enough for government work and beyond.
Ciao T
PS, lets not forget that Sound on Sound measured one specific HiFi Speaker as having 5dB power compression at rated power - with current drive the compression would be 0dB!
Hear, hear.
Absolutely right.
Well, there are several secondary terms in the equations, however I'd say that in the frequency range where the diaphragm movement of the driver is small it holds well enough for government work and beyond.
Ciao T
PS, lets not forget that Sound on Sound measured one specific HiFi Speaker as having 5dB power compression at rated power - with current drive the compression would be 0dB!
Thorsten, would the compression not result, possible partly, from non-linearity of the magnetic field, i.e. if the voice coil goes to the fringes of the field, the motor efficiency (possibly bad term) becomes less and even with perfect current drive you would get compression, no?
jd
I'm certainly glad to see that some are seeing that the Dualistic view of loudspeaker drive can be very enlightening. It is as much a paradigm changer, as anything else.
Hi,
In the case of the sound on sound test it was only the DCR change with voice coil heating that was taken into account. It was part of an early 2K series comparing "studio monitors" (KRK, Dynaudio) with "HiFi" Speakers (B&W, Warfedale).
As remarked above, in the range where diaphragm deflection is small for any funloving SPL (say above 250Hz) magnet field nonlinearity is minimised.
Here is one reason for fieldcoil speakers - fieldcoils can produce magnetic fields that fully saturate the magent system and extend the linear magnetic field range over permanent magents. Now combine that with current drive and handling mechanical problems (resonances) in a mechanical way.
We may actually be getting somewhere!
Actually, we may end up with the late 1930's "System Eckmiller" German WWII Era monitoring system (used among other applications for the first ever stereophonic recordings of music in 1943 together with AEG Tape machines, TAB Amplifiers and Neumann Condensor Mikes).
I guess time is circular after all and we are caught in a time loop, still trying to solve problems already solved before WWII shifted research to more martial ways.
😀
Nothing new under the sun.
The Eckmiller was driven by Directly Heated Penthodes without feedback and used a series crossover (no EQ) combined with a concentric acoustic system that made the points of incidence of the sound coincident too (unlike Tannoy and Altec) and had a +/-15% impedance from resonance to 16KHz (considered then a sensible upper limit of reproduction).
Talk about prior art. There is enough in this system to dismiss most patents on acoustic systems ever since...
I guess better not loose a major war again! I'm now often traveling on high speed trains running at 160Kmh as well. Without WWII and that revolting austrian Germany would have deployed trains capable of this performance in the early 40's!, not the late 70's (TEE).
Ciao T
In the case of the sound on sound test it was only the DCR change with voice coil heating that was taken into account. It was part of an early 2K series comparing "studio monitors" (KRK, Dynaudio) with "HiFi" Speakers (B&W, Warfedale).
As remarked above, in the range where diaphragm deflection is small for any funloving SPL (say above 250Hz) magnet field nonlinearity is minimised.
Here is one reason for fieldcoil speakers - fieldcoils can produce magnetic fields that fully saturate the magent system and extend the linear magnetic field range over permanent magents. Now combine that with current drive and handling mechanical problems (resonances) in a mechanical way.
We may actually be getting somewhere!
Actually, we may end up with the late 1930's "System Eckmiller" German WWII Era monitoring system (used among other applications for the first ever stereophonic recordings of music in 1943 together with AEG Tape machines, TAB Amplifiers and Neumann Condensor Mikes).
I guess time is circular after all and we are caught in a time loop, still trying to solve problems already solved before WWII shifted research to more martial ways.
😀
Nothing new under the sun.
The Eckmiller was driven by Directly Heated Penthodes without feedback and used a series crossover (no EQ) combined with a concentric acoustic system that made the points of incidence of the sound coincident too (unlike Tannoy and Altec) and had a +/-15% impedance from resonance to 16KHz (considered then a sensible upper limit of reproduction).
Talk about prior art. There is enough in this system to dismiss most patents on acoustic systems ever since...
I guess better not loose a major war again! I'm now often traveling on high speed trains running at 160Kmh as well. Without WWII and that revolting austrian Germany would have deployed trains capable of this performance in the early 40's!, not the late 70's (TEE).
Ciao T
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Hi Janneman,
Only because most people cannot read and those who can refuse to... 🙂
Those who do not know thei history are bound to repeat it...
Attached a single old sheet about the eckmiller driver in german.
Ciao T
Only because most people cannot read and those who can refuse to... 🙂
Those who do not know thei history are bound to repeat it...
Attached a single old sheet about the eckmiller driver in german.
Ciao T
Attachments
And Alan Blumlein's stereo 1934 recording of the London Philharmonic Orchestra, among others he made during that era don't count....why?😉
Hi,
I guess because EMI shut down Alan Dower Blumlein in '34 and I never really heard of his (luckily surviving) recordings (which is a shame - he deserves the credit)
So I shall settle merely for the first high fidelity stereo recordings and the first stereophonic tape recordings for Germany, let the British claim stereo even though through an engineer of germanic extraction. 🙂
Shame he died so early.
Ciao T
I guess because EMI shut down Alan Dower Blumlein in '34 and I never really heard of his (luckily surviving) recordings (which is a shame - he deserves the credit)
So I shall settle merely for the first high fidelity stereo recordings and the first stereophonic tape recordings for Germany, let the British claim stereo even though through an engineer of germanic extraction. 🙂
Shame he died so early.
Ciao T
Yes, I did.SY said:
There's only the problem that the systems described at his website don't quite represent current drive, as I have remarked in post #10.
??? It is astonishing how some are prone to take personally remarks that are totally impersonal. I cannot undrestand your reaction at all.anatech said:
Your tactics and motives for being here are becoming increasingly clear. This is the Vendor's Bazaar. If you dislike the product offered and dislike the style or anything I say, and you already 'know' so many things and learn nothing new, then you only need to stay away. I'm not in need of your endless counseling and condemnation.anatech said:
A falsehood. I have written 19 posts here, most of which contain clear technical discussion about the relevant issues. I am still willing to answer any clearly defined and relevant technical questions as far as I have time; despite that this is not a correct place to go in details. I even attached the plot in post #66 to enhance discussion, but it didn't interest you very much. It's still there. Go on and discuss it!
When your claims are proved wrong, you resort to totally absurd comments that don't have any connection to the subject at hand.
You implied that I would have recommended some material that you then found void of real worth. This was a misrepresentation and had to be corrected. Also, any work must be subject to due criticism. There must not be taboos at least in technology.
The instantaneous sound pressure radiated by the diaphragm is proportional to the instantaneous acceleration of the same, not to the instantaneous displacement, as I already stated in post #49. This is a quite easily provable and measurable hard fact. Yet the whole loudspeaker industry is stuck in the conception that pressure follows displacement and that this displacement then could be magically controlled by minimizing the output impedance and moving mass.
Striving to control the displacement is striving to control the second integral of the signal instead of the signal itself.
The book is not so math-oriented as the preview pages easily lead to understand. The ideas should be understandable at many levels, even without much equations.john curl said:
Actually, one cannot do this way in either mode if the pure driving mode is to be preserved, but the dualism also holds in this.janneman said:
There is dualism with regard to frequency response and impedance issues; but concerning distortion and interference effects, one way is more ideal than the other.
In fact, there is also a THD measurement of the voltage/current conversion, but harmonic distortion in general is not the most important factor, and the various effects can be demonstrated otherwise.Juergen Knoop said:
Hi ETM,
I also wanted to see if your viewpoint was as extreme as the books title would suggest.
Instantaneous acceleration must track the input signal by a constant. If not, the driver introduces an aberration (distortion) in the force or acceleration it applies to the air (or water if you're designing a hydrophone). The acceleration creates a displacement, which is another way of saying that the speaker cone travels over some distance. If your integral is such a small value that the distance tends to zero, you have proved that distance and displacement are irrelevant. But, at the same time so is your point. The force (acceleration) that doesn't travel any distance is of no use other than a mental construct. Remember that force x distance = work. No distance = no work. Cute concept, but not useful.
-Chris (I don't even know what you're arguing about now 🙂 )
Well, imagine if someone had answered you in that way. It wasn't pretty.
Just in case there are any misunderstandings then, I only wanted to talk with the author to see where your look at these things from. It helps to understand the viewpoint of a person who is trying to get their message out.
I also wanted to see if your viewpoint was as extreme as the books title would suggest.
It's in my nature to help, and to draw attention to areas that could use some polish. I'm not perfect, but I don't fail to see both sides of a situation. You complained that your book was not well received by the AES. I have no love for that organization either, but I didn't know how stuck in the sand you and the AES were. You are both pretty darn stuck if you ask me. Yeah, I know. You didn't ask.
I said I was interested in the topic. I said I had some experience with the material. I'm not so arrogant as to think I know everything, so I ask when I'm not sure on something, or if some material contradicts what I've seen before. You would do at least the same.
Okay, I guess this is open to interpretation on at least two sides. I'm just going to see where you go in that case.
Okay, so I guess you are saying your amplifiers have no voltage limits then? Allow me to clarify what I was saying as it's clear only a simulator is unlimited. When we are detecting safe limits for a conventional power amplifier, we most often are worried about what electrical quantity? If you answered "current flow", you'd be correct. As we in agreement as far as a simple system is concerned? Fancy second breakdown curves are not considered to avoid a silly argument. Now, in a current amplifier, we aren't normally worried about running out of voltage as the amp would simply clip and place a limit on the available current flow. However, this would generate high distortion along with high levels of harmonics that might overpower a tweeter in a multi driver system on a single amp. So, you would wish to avoid this situation - yes? In other words, you have to deal with a voltage limit. Another aspect is the total power dissipated by the output devices. This is the same issue no matter if the amp is current or voltage drive. Current x voltage = heat, no matter what the device is doing. Therefore, for this aspect, a current drive amplifier is on the same level as a voltage drive amplifier. My comments were an attempt to show you that both amplifier types faced similar real world problems. That's in answer to your total dismissal of the current technology that is most often used to energize loudspeaker systems. If you were not so totally blind to anything that differs from what you see is an improved concept, you could then come across as a balanced and reasonable person. Again, just a reference to how inflexible you seem to be.
No, that's not what I said at all. I said I read the material for one.
Well, that is true in near field for sure. This same concept has been used with those impossibly small sub woofer systems like the Sunfire sub. They decided to throw out Thiel and Small all together and treat the woofer surface as a movable surface. The idea being that with enough amplifier power, you could treat a speaker more like a piston. It works. One of the hallmarks of a driver suitable for this is that it is incredibly stiff. You can usually stand on a cone (before assembly in to a driver unit) without damaging it or modifying it's shape. I actually was standing on one, it may have been an Epos unit. I was also lucky enough to talk to the designer for some time on it. However, none of this has anything to do with the type of amplifier you drive the speaker with.
Do you mean a plural of the word, Tabu? I would agree with you there. It took a couple readings to figure out what you were saying.
If you intend to transfer energy into the air, you generally do this through displacement. You move a volume of air, there is no way around this. If you were to take a screen and accelerate it, there would be darned little acoustic energy created - right? You can accelerate air all you want, but to do this without any displacement wouldn't buy you anything - assuming it were possible to do this in the first place. The entire concept of displacement is part of acceleration, you can not separate the two. To accelerate anything implies movement. If that thing is physical, it will have dimensions, and therefore cover an area. If you move that area, or displace it, the moving area will cover a volume of whatever is surrounding it. Real world now. An isolated mathematical idea has no value unless you tie it into what actually occurs. There is a guy named Stanley Lipshitz who enjoys arguing in a very similar fashion to how you do. I figure the two of you would get along famously. BTW, he's well entrenched in the AES and various committees. I don't believe he would have been consulted on your book under consideration, so he may be a "friendly". You should really look the man up. He works out of the University of Waterloo here in Ontario, at least he did last time I looked.
What you are actually talking about is the idea of matching the impedance of the "air exciter" (for lack of a better term) to the impedance of the medium you wish to excite. Horn type enclosures are an attempt to make an acoustic transformer to make the match closer to unity. It also transfers more energy to the air per unit energy in. In other words, the efficiency of the air - loudspeaker system goes up. Just like in electronic power transfer theory. This would also hold true for anything you attempt to do, a more efficient coupling between a loudspeaker and the air has exactly zero to do with how you go about energizing that speaker. I don't even know why you brought this up since it applies equally to each system.
Now, as far as controlling the second integral, that is exactly what must happen to produce low distortion sound. After all, the heating of the voice coil reduces the displacement, and that is distortion (compression, or amplitude distortion). Another would be an uneven magnetic field that decreases the motor strength near each extreme of the displacement of the voice coil. Again, we have a reduced displacement as a result, which is again amplitude distortion.
Instantaneous acceleration must track the input signal by a constant. If not, the driver introduces an aberration (distortion) in the force or acceleration it applies to the air (or water if you're designing a hydrophone). The acceleration creates a displacement, which is another way of saying that the speaker cone travels over some distance. If your integral is such a small value that the distance tends to zero, you have proved that distance and displacement are irrelevant. But, at the same time so is your point. The force (acceleration) that doesn't travel any distance is of no use other than a mental construct. Remember that force x distance = work. No distance = no work. Cute concept, but not useful.
-Chris (I don't even know what you're arguing about now 🙂 )
If you put a correctly designed copper ring or cap into the voicecoil gap it does not matter any more if the amp has current or voltage drive. The remaining issue is heating of the voicecoild but that can be solved with mechanical design too.
Distortion of the current that is send back to the amp due to mechanical unlinearity and design of the magnet system can be solved mechanical too. Turning the world up side down to cutrrent drive is impossible anyway because the market has already decided on voltage drive. So it is much more productive to find solutions that work with voltage drive.
Distortion of the current that is send back to the amp due to mechanical unlinearity and design of the magnet system can be solved mechanical too. Turning the world up side down to cutrrent drive is impossible anyway because the market has already decided on voltage drive. So it is much more productive to find solutions that work with voltage drive.
ETM, I have received your book as yet, but I hope to comment more when I get it. Keep up the good work.
I can well imagine, and it won't move me a jot if someone said his book has a certain target audience.anatech said:
This is personal assault and something one would not expect from a moderator. An apologize would be in order.anatech said:
Again, a totally irrelevant comment that has nothing to do with the subject, that was the distortion caused by the nonlinearity of driver inductance.
Again, absurd commentary that is not related to what I said.
Again, totally irrelevant verbiage. I have never said that acceleration can occur without displacement.
No, I'm not talking about such things. Output impedance is a property of amplifiers.
The nonidealities of the voice coil and magnetic system have nothing to do with the fundamental principle that I stated.
Rubbish again. I have never denied the existence of displacement.
It is for this reason that I think it would be easier to discuss this in differential equation form, (hopefully, DOT notation) where we can get a feeling as to the changes that occur, when we use either voltage or current drive. It would also be easier to then 'play' with the constants of compliance, damping and mass, respectively and get a solid feel as to what we can do to optimize each condition.
What's the hangup with dot notation? That's only time derivatives. A differential equation is a differential equation.
Dot notation is easier to write, and I find it easier to conceptualize the tradeoffs in speaker variables. This is most probably why Rice and Kellogg used it, and why J. Manger also used it. It is only a serious suggestion to the book's author, as his generalized equation on page 338 (I believe) is difficult to relate directly to the specific loudspeaker tradeoffs by those who are not comfortable with differential equations.
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