Now we finally get to your objection -- Esa's enthusiasm for the topic. Here we often run into people's exuburence... i tend to just pay no attention to it and look for the meat.
Further, he has no need to prove his enthusiasm, or any way to do so. Each individual can only prove, or disprove, it to themselves ny building or hearing a current drive system for themselves. This book is for people already having an interest in current drive.
Esa's enthusiasm is irrelevant to the fact that this is a good practical guide/cookbook to current drive. He does the derivations, he does the math, provides real world data to back up what is revealed, provides a practical guide to building amplifiers and a specfic design (with circuit board layout), what considerations need to be considered when designing speakers, and 2 sorted loudspeaker designs.In the back are a number of technical appendice to help understand the math used.
For anyone who has had their interests in current drive piqued by comments & works of any of the luminaries mentioned in Post #56, the arrival of this practical guide is well timed. And it is dirt cheap.
Having read it, and starting to reread it, i would recommend it to anyone who wants to learn more about current drive. It is not math-lite, one has to suspend judging Esa's enthusiasm which breaks thru the technical, and one has to make a bit of an effort sometimes to deal with the Finnish accent.
dave
Hi Dave,
You are well aware that I do cut people some slack, and that I will consider alternate viewpoints. I feel you have not seen anything past your support of Esa's efforts here.
Make no mistake that the prime motivation for this thread here, and on other web sites, has been to advertise and bolster sales for this book. I normally don't have a problem with this - within reason. My personal opinion is that the exaggerated position he takes along with the extreme comments makes it impossible for him to educate others. There must be an acknowledgment for the strengths of each approach (current and voltage drive). In fact, in attempting to find out additional information from Esa, I have supported and recognized the positive attributes with current drive.
I feel that your comments have trivialized my position unfairly. Just because this book touches on a topic that you find interesting (as do I) is no reason to turn a blind eye to the rest of Esa's attitudes and lack of a balanced (healthy) outlook. The attitude can not be separated from the information in the book, or in posts anywhere. For anyone to achieve success, they need to learn how to present their point of view and actually consider points other people raise about the subject. I do not believe he can objectively make any decisions regarding the real performance and hence any reliable recommendations.
You say the book is not expensive, and that anyone interested should buy the book and perform the experiments or projects as laid out in that book. The cost of the book is immaterial to be honest with you. The main issue is that Esa has not provided any measured performance data at all. Therefore, I don't think he is qualified to make any suggestions as to how power should be delivered to speakers. In fact, the papers which were linked to earlier in the thread were written by authors that had in fact performed real tests and recorded the resulting data. Yet, Esa feels compelled to say that these authors do not properly understand the subject. I can not accept this position or any conclusions reached by Esa until such time that he does perform testing on his physical prototypes. Only then will the operational performance and problems become known. Only then can any recommendations be made.
The authors who have made these reports and performed proper experiments allow access to their work at no charge. They also do not comment negatively on the work of others in their field of study. Esa has directly challenged the current state of the art and also previous work on current driven loudspeakers. I'm sorry, but the onus is on him to address concerns and questions about his own work. It is not up to any groups of people to expend their own time and money to provide experimental data. Of course, there is nothing to stop anyone from doing this either. But I don't see how anyone can recommend purchasing this work under these circumstances.
I have nothing against Esa at all. I do not like the situation and atmosphere though. I would otherwise happily support his work as I have done with other works and concepts. To suggest otherwise is not being fair to me at all.
-Chris
No. I'm afraid that you have both mis-labeled what I see in Esa's approach, and the fact that the way and manner with which this topic was posted in a public forum is a problem in of itself.
You are well aware that I do cut people some slack, and that I will consider alternate viewpoints. I feel you have not seen anything past your support of Esa's efforts here.
Make no mistake that the prime motivation for this thread here, and on other web sites, has been to advertise and bolster sales for this book. I normally don't have a problem with this - within reason. My personal opinion is that the exaggerated position he takes along with the extreme comments makes it impossible for him to educate others. There must be an acknowledgment for the strengths of each approach (current and voltage drive). In fact, in attempting to find out additional information from Esa, I have supported and recognized the positive attributes with current drive.
I feel that your comments have trivialized my position unfairly. Just because this book touches on a topic that you find interesting (as do I) is no reason to turn a blind eye to the rest of Esa's attitudes and lack of a balanced (healthy) outlook. The attitude can not be separated from the information in the book, or in posts anywhere. For anyone to achieve success, they need to learn how to present their point of view and actually consider points other people raise about the subject. I do not believe he can objectively make any decisions regarding the real performance and hence any reliable recommendations.
You say the book is not expensive, and that anyone interested should buy the book and perform the experiments or projects as laid out in that book. The cost of the book is immaterial to be honest with you. The main issue is that Esa has not provided any measured performance data at all. Therefore, I don't think he is qualified to make any suggestions as to how power should be delivered to speakers. In fact, the papers which were linked to earlier in the thread were written by authors that had in fact performed real tests and recorded the resulting data. Yet, Esa feels compelled to say that these authors do not properly understand the subject. I can not accept this position or any conclusions reached by Esa until such time that he does perform testing on his physical prototypes. Only then will the operational performance and problems become known. Only then can any recommendations be made.
The authors who have made these reports and performed proper experiments allow access to their work at no charge. They also do not comment negatively on the work of others in their field of study. Esa has directly challenged the current state of the art and also previous work on current driven loudspeakers. I'm sorry, but the onus is on him to address concerns and questions about his own work. It is not up to any groups of people to expend their own time and money to provide experimental data. Of course, there is nothing to stop anyone from doing this either. But I don't see how anyone can recommend purchasing this work under these circumstances.
I have nothing against Esa at all. I do not like the situation and atmosphere though. I would otherwise happily support his work as I have done with other works and concepts. To suggest otherwise is not being fair to me at all.
-Chris
We should hope that is the case, this thread is in the Vendor's Forum
Seems an opinion shared by Malcolm Hawksford (althou stated in a subtler way as one would expect for a Brit writing an AES paper):
Esa also shows people how to apply the techniques to multiways with passive XOs.
My speaker will be 1-way with no passive filters.
It is in the book. And as you said... in the paper's previously quoted.
dave
I referred to the fact that some tube amps have relatively high output impedance (i.e. they are some steps toward current drive) and that this can quite well explain the positive sonic attributes often associated to them.tryonziess said:
anatech said:
anatech said:
anatech said:
anatech said:
For those who like to know: There are two complete speaker prototypes designed, built, measured and tested; the frequency responses and photos are also provided. They have served well for years and are still in my active use. I'm also planning an interesting new project that in time will be published in the website. Availability of the drivers has only caused some problems, as Tymphany has discontinued almost all of the Vifa brand. I have found a substitute for one woofer but not yet for the other.anatech said:
Below is a plot of how the impedance magnitude of a typical hi-fi driver changes at 2 kHz frquency as a function of cone displacement. The drivers tested were A: Vifa M13SG-09-08, B: Seas P14RC4Y/DC, and C: Peerless 833429. In each driver, the measurement has been extended to the rated Xmax limit. The displacement was actuated mechanically and measured with a scale. This is only one out of the many disastrous effects voltage drive is beset by and not necessarily the most serious.Terry Demol said:
An externally hosted image should be here but it was not working when we last tested it.
Due to changing inductance, or inductive EMF, the impedance typically varies +/- 10% within a driver's linear excursion range. This means that on voltage drive a 2 kHz tone reproduced by the same driver exhibits +/- 10% amplitude modulation with accompanied phase modulation also. According to basic theory of amplitude modulation, the distortion components thus generated amount to 5% of the original amplitude, giving rise to a full 7% of total intermodulation distortion, all this eliminable by current-drive operation. Unlike the Bl variation, this phenomenon becomes significant already at relatively low excursions.
WRT signal modulated inductance - yes this is well understood.
Ref link I posted, IMD plots of TD12M, driver with very low L modulation.
Non-linear Distortion (drivervault)
Have you verified the above theory with similar IMD measurements of
current driven speakers?
Thanks
T
Hi Dave,
I think the points I made are justified. In fact, TheSeekerr has put the issues in a nutshell for you.
I do not believe an author should expect anyone to purchase a technical book from an unknown author without being able to see that the book can stand up to peer review of some sort.
Normally what happens in a bookstore, one can walk up to a book they are interested in and flip through some pages. That way they can determine for themselves if the book might be useful to them. In the absence of a bookstore, the only other way to do this is to give the author the chance to explain his viewpoint and back some statements up. In no way does Esa stand the risk of telling all, losing sales as a result.
-Chris
I think the points I made are justified. In fact, TheSeekerr has put the issues in a nutshell for you.
I don't know about you Dave, but I only purchase a book when I have a fair idea what it covers and how likely it is to be correct. I have at least three book cases packed full of books to prove I'll pay for what I get use out of.
I do not believe an author should expect anyone to purchase a technical book from an unknown author without being able to see that the book can stand up to peer review of some sort.
Dave, I'm not exactly sure what you are saying here. Everyone is entitled to their opinion, and with Malcolm Hawksford you can see that he does consider both sides. The man even ran experiments before the paper was written. He can back up what he says on the strength of what he has seen in the experiments, and his career in audio.
That's good for content, but it has nothing to do with what the current issues are that we are talking about.
That's all well and fine, but there are reasonable questions that have been asked of the author which have not had a reply. Anyone who is confident they are on the right track would be happy to field questions. This is a very good way to promote a book and will interest other people who might not otherwise take notice of the publication.
Normally what happens in a bookstore, one can walk up to a book they are interested in and flip through some pages. That way they can determine for themselves if the book might be useful to them. In the absence of a bookstore, the only other way to do this is to give the author the chance to explain his viewpoint and back some statements up. In no way does Esa stand the risk of telling all, losing sales as a result.
-Chris
Hi Esa,
Also, the geometry of the V.C. gap and voice coil itself will have a large effect on linearity. Some drivers will be more linear than others in this regard.
I think too that every technology has both pluses and minuses associated with them. Everyone knows and accepts this. A balanced presentation that draws reasonable conclusions will attract far more people than an all or nothing stance.
I normally use Peerless drivers, but for some applications the Vifa product fits the application better. Now we have a bunch of unknown products that need to be tested in order to know where they work well.
Did they give you an answer for shutting down the Vifa line? From where I sit, Vifa seemed to sell more strongly than the other drivers. Could it be the markup (they don't make enough money on these)?
Thank you for your response Esa. They are some other questions back in the thread, if you could review them and possibly comment.
-Chris
Perfect! Thank you very much for posting this.
I can see what you mean, and this does help illustrate the point you are making very well for those members who are not that familiar with speakers and distortion mechanisms. The only thing that I think may hurt you is the exaggerated wording you tend to use. It is sufficient to state that this is a shortcoming, or problem that voltage drive suffers from. Going back to find a similar issue with current drive and showing that the order of magnitude is lower for current drive. Extreme positions and wording will tend to make people suspicious.
Also, the geometry of the V.C. gap and voice coil itself will have a large effect on linearity. Some drivers will be more linear than others in this regard.
I think too that every technology has both pluses and minuses associated with them. Everyone knows and accepts this. A balanced presentation that draws reasonable conclusions will attract far more people than an all or nothing stance.
Yes, that is a shame.
I normally use Peerless drivers, but for some applications the Vifa product fits the application better. Now we have a bunch of unknown products that need to be tested in order to know where they work well.
Did they give you an answer for shutting down the Vifa line? From where I sit, Vifa seemed to sell more strongly than the other drivers. Could it be the markup (they don't make enough money on these)?
Thank you for your response Esa. They are some other questions back in the thread, if you could review them and possibly comment.
-Chris
http://www.amazon.com/Current-Drivi...=sr_1_2?ie=UTF8&s=books&qid=1268628806&sr=8-2
Click on look inside
dave
I'll have to disagree with you Chris. Feel free to not buy the book.
I did, and after reading it, i'd buy it again. I am actually buying another copy for someone else because i figure it will be valuable to them. I'd recommend it to anyone interested in current drive, and say that for anyone thinking of making a Pass F1 or F2 it is a muct have.
I'm encoraged by it to make a speaker for current drive. Already have the amplifier.
dave
I did, and after reading it, i'd buy it again. I am actually buying another copy for someone else because i figure it will be valuable to them. I'd recommend it to anyone interested in current drive, and say that for anyone thinking of making a Pass F1 or F2 it is a muct have.
I'm encoraged by it to make a speaker for current drive. Already have the amplifier.
dave
It is easy to change an amplifier from voltage to current drive. I'm curious about the feedback resistor though. Is there any possibility of this resistor causing distortion with thermal issues?
Also, stability concerns have changed dimensions. Now you are worried about inductive loads causing instability, whereas before it was capacitive loads with voltage drive. Is it necessary to redefine stability compensation in such an amp? (or perhaps, stability will actually be easier, since current drive is more natural for an inductor...)
- keantoken
Also, stability concerns have changed dimensions. Now you are worried about inductive loads causing instability, whereas before it was capacitive loads with voltage drive. Is it necessary to redefine stability compensation in such an amp? (or perhaps, stability will actually be easier, since current drive is more natural for an inductor...)
- keantoken
Anatech, maybe this should help!
Current-Driving of Loudspeakers
Did anyone here even know this site exists? Not even the author mentioned it, but I found the URL in the front page of the book preview.
- keantoken
Current-Driving of Loudspeakers
Did anyone here even know this site exists? Not even the author mentioned it, but I found the URL in the front page of the book preview.
- keantoken
Assuming that magnetic coil force is dependent on coil current and independent of all else:
If the speaker resonates, current generated in the coil replaces the current provided by voltage drive, and so the speaker could be said to be "driving itself". (While the shorted coil serves to dissipate the motional energy of the cone (as in dampening), maybe it's magnet nonlinearities or something that cause distortion here? Modulating coil resistance?)
However, if we use current drive, EMF from the coil turns into voltage. As this voltage has no discharge path through the coil, it cannot dissipate in it as magnetic force.
Perhaps the self-dampening properties of the voice coil under voltage drive do not outweigh the consequences of current drive. Maybe this can be likened to telling a ball to fly rather than just picking up the ball and throwing it. Current drive is the "direct method" of loudspeaker operation, whereas in voltage drive you're perhaps giving the speaker too much control over itself; the loudspeaker itself has nothing to contribute to the experience, so we shouldn't let it run the show. Self-dampening is convenient, but it doesn't appear that we can trust the coil to do it well, if what Esa says bears out.
Also, microphonics may be significant at loud volumes, or if for some reason you put a woofer in the same enclosure with a midrange driver. From the midrange driver moving in and out with the bass, this movement will add to the dissipation of the voice coil, adding to the resistance modulation. At volumes where the resistance is modulating or near modulating, this affect can't contribute. Of course this is an extreme case. However I'm sure it's the same with separate enclosures to some degree as well.
I've been reading the Google books preview, and I'm definitely impressed.
- keantoken
If the speaker resonates, current generated in the coil replaces the current provided by voltage drive, and so the speaker could be said to be "driving itself". (While the shorted coil serves to dissipate the motional energy of the cone (as in dampening), maybe it's magnet nonlinearities or something that cause distortion here? Modulating coil resistance?)
However, if we use current drive, EMF from the coil turns into voltage. As this voltage has no discharge path through the coil, it cannot dissipate in it as magnetic force.
Perhaps the self-dampening properties of the voice coil under voltage drive do not outweigh the consequences of current drive. Maybe this can be likened to telling a ball to fly rather than just picking up the ball and throwing it. Current drive is the "direct method" of loudspeaker operation, whereas in voltage drive you're perhaps giving the speaker too much control over itself; the loudspeaker itself has nothing to contribute to the experience, so we shouldn't let it run the show. Self-dampening is convenient, but it doesn't appear that we can trust the coil to do it well, if what Esa says bears out.
Also, microphonics may be significant at loud volumes, or if for some reason you put a woofer in the same enclosure with a midrange driver. From the midrange driver moving in and out with the bass, this movement will add to the dissipation of the voice coil, adding to the resistance modulation. At volumes where the resistance is modulating or near modulating, this affect can't contribute. Of course this is an extreme case. However I'm sure it's the same with separate enclosures to some degree as well.
I've been reading the Google books preview, and I'm definitely impressed.
- keantoken
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In fact, I had in mind to change that word, but in a haste it slipped.keantoken said:
Yes, such a change is possible, but the stability of the design should be verified with a real-world load, as with any new design. A series RC arm in parallel with the load is usually sufficient, but sometimes high frequency oscillations are so subtle (regardless of the driving mode) that only an oscilloscope can tell it. Resistors usually do not cause distortions, and the current-sensing resistor doesn't consume very much power.
Maybe I've heard somewhere about it.
The relative proportion of the microphone EMF in a driver's voltage is independent of the signal level, but is a strong function of driver sensitivity. In low-sensitivity hifi drivers, this cabinet noise feedback is several percents, but in a typical PA speaker many times higher. This can explain much of why PAs sound as they sound.
Hi keantoken,
Hi Dave,
Dave, we disagree. That much is obvious and I can even accept it. I thought I was both clear and fair in the points I brought up. One thing that surprises me is that I've made it clear I was familiar with current drive, and yet you seem to assume I have little knowledge of what is going on. Odd, because we do agree on many points. I didn't expect such a strong reaction from you of all people.
Now, did you notice that Esa kindly posted some of the information we wanted to see? I even thanked him, and my appreciation is genuine. I may experiment with current drive some more in the future. Until then, I am enjoying my sound system that seems to work fine in spite of the serious problems that plague the technology used. I just realized that I have spent the better part of my life supporting a failed technology Dave.
I am very happy that you enjoyed the book and found it educational. I can't comment as I have not purchased the book.
Hi SY,
-Chris
That's the first place I went, and read.
Click on the member's name and select "home page". You're there.
Hi Dave,
Gee, I didn't know I had to opt out.
Dave, we disagree. That much is obvious and I can even accept it. I thought I was both clear and fair in the points I brought up. One thing that surprises me is that I've made it clear I was familiar with current drive, and yet you seem to assume I have little knowledge of what is going on. Odd, because we do agree on many points. I didn't expect such a strong reaction from you of all people.
Now, did you notice that Esa kindly posted some of the information we wanted to see? I even thanked him, and my appreciation is genuine. I may experiment with current drive some more in the future. Until then, I am enjoying my sound system that seems to work fine in spite of the serious problems that plague the technology used. I just realized that I have spent the better part of my life supporting a failed technology Dave.
I am very happy that you enjoyed the book and found it educational. I can't comment as I have not purchased the book.
Hi SY,
Completely agree, no matter what technology is used to make sound.
-Chris
Something to think:
The Audio Engineering Society (AES) has refused to publish any advertisement of the book in their journal!
This became clear when I submitted this file to them.
Interesting enough?
Their justification:
"... A book advertisement assumes that the AES has no conflict with the content, and that isn't quite appropriate. We certainly don't want to suppress your ideas, but we feel the advertisement route is not correct." (John Vanderkooy, Editor)
I further tried to inquire what do they exactly mean by the implied 'conflict' between the AES and the book content (which they haven't seen) and asked them to point out any published journal articles or other valid documents that could make up such a conflict. I wasn't given any. Rather, I was informed that "The fact that almost no systems exist that employ current drive speaks to the industry rejecting this view. It is easy to make amplifiers deliver current drive; that is no objection."
Draw your conclusions!
The Audio Engineering Society (AES) has refused to publish any advertisement of the book in their journal!
This became clear when I submitted this file to them.
Interesting enough?
Their justification:
"... A book advertisement assumes that the AES has no conflict with the content, and that isn't quite appropriate. We certainly don't want to suppress your ideas, but we feel the advertisement route is not correct." (John Vanderkooy, Editor)
I further tried to inquire what do they exactly mean by the implied 'conflict' between the AES and the book content (which they haven't seen) and asked them to point out any published journal articles or other valid documents that could make up such a conflict. I wasn't given any. Rather, I was informed that "The fact that almost no systems exist that employ current drive speaks to the industry rejecting this view. It is easy to make amplifiers deliver current drive; that is no objection."
Draw your conclusions!
Attachments
Hi Esa,
I'd have to agree with SY on that. Just the tone of how you've presented your ideas here has been the reason for most of my concerns. Your ad as designed certainly would be at odds with any professional publications image.
Engineers are a conservative lot. That means they don't react well to a great lot of controversy or noise that may surround an alternate approach to something as common as driving a transducer to create sound.
-Chris
I'd have to agree with SY on that. Just the tone of how you've presented your ideas here has been the reason for most of my concerns. Your ad as designed certainly would be at odds with any professional publications image.
Engineers are a conservative lot. That means they don't react well to a great lot of controversy or noise that may surround an alternate approach to something as common as driving a transducer to create sound.
This one post covers just about everything I can imagine would be a fix for the way you presented your ideas. Read it a few times and let it sink in.
That is the conclusion I come to. In fact, this is about what I had said earlier on in this thread. If you present your ideas as just another way to drive a speaker instead of the only proper way to drive a speaker, all my objections evaporate. It becomes a view I can support.
-Chris
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