Speaker Dave!
tsk tsk...
you know, i expect that the BL curve matters.
also that the move to Alnico PM was mostly economic and size/weight.
you save complexity, wires, PS, and keep HV away from the consumer...
ferrite was the same deal, cheaper, smaller, lighter, not necessarily better.
imo it is entirely possible that a FC version of the otherwise identical speaker will sound different. Given that almost everything else that gets changed seems to make a difference, why not this??
or, are you in the "all amps with less than 0.xxx% distortion sound the same" camp?
_-_-bear
by BL curve you mean the B vs. X? No reason why this would need to be any different given the same gap geometry and saturation.
Since all the dramatic differences always described disappear when we move to blind testing, then we should all be sceptical. That "everything changed seems to make a difference" is exactly what I doubt the most.
Where is the science? Where is the proof? It isn't enough to just believe.
David
It was a neat trick, but it didn't work that well. The coil usually was placed in series with the B+ feed to the RF, IF and low level audio stages, limiting the amount of current through the coil to well under the 100 milliamp range. It also imposed a hum component at a very bad point: the speaker magnet system, which required the use of a hum bucking winding on the voice coil to cancel out at least some of the hum. Still radios with field coil speakers always had more residual hum level than their PM speaker counterparts. Nobody in the radio business was sorry to see FC speakers go. The PM speakers were cheaper, more efficient, and generally gave better sound
The real powerhouse field coil speakers in PA systems and jukeboxes usually had a parallel power supply with high voltage/low current.
OK. But I don't want to convince anybody. Why should I? A great engineer must try then he can understand why. Not the opposite!
There are many mechanisms inside chips not 100% clear, but they work.
I don't want and I don't need to prove anything. I simply say: TRY.
I hope you try. Nothing else. It's very interesting to try to understand why they are so different in sound, but this is another story. We talk about theory for months. Then? Which results?
If you want to check this difference you need to try. Then we can discuss about why...
Someone alse already replied you about alnico and ferrite etc...
From a "high qty" point of view FC has no meaning. Ferrite has been a huge improvement to decrese costs and to reach good results.
No, we are just talking about the border here. No nostalgia.
That's all
Enjoy!
Fabio
It would be easier to "Try" if those who have made a few field-coil conversions would share some practical knowledge. I don't see any of the here. Isn't this DIYaudio?
I think the reason chips work is because they ARE very well understood by the designer using well known engineering facts and science.I suggest you make the same claim to Intel and see how much they laugh.
As for theory, how do you think reasons for why things work come about? Did you post any DBT or was it just more "I know what I heard" subjective opinion? I have yet to come across anyone with calibrated ears no matter how much they claim to be able to hear dramatic differences.Were the speakers that were modified measured before and after? Hard work, money spent and a pretty driver will affect your hearing bias.
Just pointing out that Alnico versions were MORE expensive than same speaker in f.c. version back in the late 1930s.
Field coils also also provided savings by replacing smoothing chokes or bleeder high power resistors with the field inductance.
Size and weight savings of PM cost more.
I don't know if they could get the highest possible flux with the pre-Alnico V magnets of the time. Perhaps the very top end still belonged to the electrodynamic motors. Jensen A12 field coil had a bit higher flux density than the A12PM.
But that was then...and this discussion is mostly about NOW.
As for "proof" and all that, the way to do this is to listen to a driver in PM and field coil implementations as closely matched as possible for flux in the gap, see if you can hear a difference. IF there is a difference then you have something requiring explanation.
People who have done this or experiments approaching this, such as the Wolf Von Langa's Altec field conversions or comparing Lansing Mfg. Company field coil 287 with early Altec 288 (which I have done) report big differences.
More control would be useful to placate the naysayers. Maybe they should be the ones to do the experiments.
I own Jensen A12 and A12PM but I don't know if I can trust that the flux of the PM is at spec, and the electrodynamic version did have higher specified flux density. Also with drivers that old, condition of each specimen is questionable. I will try to compare them when I get some free time.
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Well, since 99% of the posters on here won't have access to both types of drivers then listening to compare is out.
Got any links showing some DBT tests or for that matter any measurements at all involving your above mentioned "big differences"?
Sorry but it's always up to the ones who brought up that they can hear "big differences" to show that what they claim is true not the other way around. Will you or anyone else singing the praises of field coils do so? Doubtful.
Not true. I studied electronic engineering (years ago, to tell the truth) but one of the main interesting things I did learn was that extreme chips worked for statistical reasons. True, science, facts and... statistics. They were studying the reasons why the chips did not follow 100% the theory. So they were studying new math for it.
This has been told by top designers and researchers during my final master project. They made clear examples I don't list here.
I'm sorry if you thought that all is predictible... It is not.
That was when I learned about the true scientific approach. We study the theory, design the item, we try and check the results. Then we improve the theory and try again. Nothing new, just PDCA.
Intel designers don't laugh... Even in this case, I don't want to convince you... If you wish, you can try...
Enjoy
Fabio
I agree 101%. I asked twice here, but still no news.
I never tried myself, designing and building. I designed a special power supply, yet.
Fabio
Availability of twin versions of the same speaker is indeed a practical problem but these are a few opportunities to do so.
As for DBT...hahaha. Most differences are not that subtle and I don't think that experienced listeners are so inept at framing listening comparisons that there is a real need for the magic curtain approach.
Let's not derail another interesting thread with the primitive objectivist/subjectivist debate. This is like sticking one's fingers in the ears and saying NANANANANA when the discussion doesn't go down the favored path.
The trajectory of philosophy of science of the 20th century maps the rejection of this simpleminded notion of objectivity and the sort of logical positivism underlying many diyforum "objectivist" bum rush hit jobs. This is true for hard sciences as well as human sciences.
The reality is that objectivity and all knowledge and discovery procedures are social constructions. Objectivity is a religious belief of sorts. It's definition is cultural.
Pretending otherwise has actually served very well to organize practical technical work, but this is a useful fiction rather than a fundamental characteristic of the cosmos.
For a familiar example that blows this "objectivist" nonsense out of the water think about Heisenber's uncertainty principle.
If you really start looking into these questions of how humans interface with the phenomenal world, which it seems none of the local self-declared 'objectivist thugs' have done, very profound subject/object dialectics emerge.
Logical positivism of the sort underpinning these behavioralist clinical experiments was rejected by the positivists themselves by the 1950s.
But that is a reaction based on 10 years of graduate education in related fields and I can't expect audio guys to think like an anthropologist. the point of anthropology and philosophy of science training is to illuminate and problematicize areas of experience and cognition that "civilians" aren't often aware of in daily life.
What I do find curious how people who never heard 'x' are insistent that 'x' can't be, and then shift the burden of proof to the person who did the work and went out and listened.
I say get off your lazy @$$ and listen to some field coils!! Don't tell the guy who did listen to go out with Clio and an Audio Precision and prove it to you while you sit at the computer in your underwear.
I'd think "observation" would be a highly-valued exercise among objectivists.
I heard a lot of field coils and I think there is a distinctive character to the field coils. Steve Schell, who is probably too smart to get into this discussion, says the same thing.
That said, I think the technical dissection in this thread is interesting...but the "prove it to me on my terms" bit is non-productive.
Do we even know what the terms are? I am not sure it is "flux in the gap" but perhaps flux modulation and recovery characteristics of different kinds of magnets?
I think there was a comparison of electromagnets and PMs in Sturley, "Radio Receiver Design" I'm traveling and the book is in storage anyway. Anybody have the volume at hand?
As for DBT...hahaha. Most differences are not that subtle and I don't think that experienced listeners are so inept at framing listening comparisons that there is a real need for the magic curtain approach.
Let's not derail another interesting thread with the primitive objectivist/subjectivist debate. This is like sticking one's fingers in the ears and saying NANANANANA when the discussion doesn't go down the favored path.
The trajectory of philosophy of science of the 20th century maps the rejection of this simpleminded notion of objectivity and the sort of logical positivism underlying many diyforum "objectivist" bum rush hit jobs. This is true for hard sciences as well as human sciences.
The reality is that objectivity and all knowledge and discovery procedures are social constructions. Objectivity is a religious belief of sorts. It's definition is cultural.
Pretending otherwise has actually served very well to organize practical technical work, but this is a useful fiction rather than a fundamental characteristic of the cosmos.
For a familiar example that blows this "objectivist" nonsense out of the water think about Heisenber's uncertainty principle.
If you really start looking into these questions of how humans interface with the phenomenal world, which it seems none of the local self-declared 'objectivist thugs' have done, very profound subject/object dialectics emerge.
Logical positivism of the sort underpinning these behavioralist clinical experiments was rejected by the positivists themselves by the 1950s.
But that is a reaction based on 10 years of graduate education in related fields and I can't expect audio guys to think like an anthropologist. the point of anthropology and philosophy of science training is to illuminate and problematicize areas of experience and cognition that "civilians" aren't often aware of in daily life.
What I do find curious how people who never heard 'x' are insistent that 'x' can't be, and then shift the burden of proof to the person who did the work and went out and listened.
I say get off your lazy @$$ and listen to some field coils!! Don't tell the guy who did listen to go out with Clio and an Audio Precision and prove it to you while you sit at the computer in your underwear.
I'd think "observation" would be a highly-valued exercise among objectivists.
I heard a lot of field coils and I think there is a distinctive character to the field coils. Steve Schell, who is probably too smart to get into this discussion, says the same thing.
That said, I think the technical dissection in this thread is interesting...but the "prove it to me on my terms" bit is non-productive.
Do we even know what the terms are? I am not sure it is "flux in the gap" but perhaps flux modulation and recovery characteristics of different kinds of magnets?
I think there was a comparison of electromagnets and PMs in Sturley, "Radio Receiver Design" I'm traveling and the book is in storage anyway. Anybody have the volume at hand?
I'm sorry if you thought that all is predictible... It is not.
That was when I learned about the true scientific approach. We study the theory, design the item, we try and check the results. Then we improve the theory and try again. Nothing new, just PDCA.
Intel designers don't laugh... Even in this case, I don't want to convince you... If you wish, you can try...
Enjoy
Fabio
An example of more updated and realistic model of scientific method. as I was describing.
Thanks, Fabio. See you in Munich. Let's have a Augustiner Weissbier and listen to some WE field coils!
EDIT: Make that Franziskaner Weissbier...my subjective favorite!
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I don't want to convince you... If you wish, you can try...
Enjoy
Fabio
Sorry but I don't accept your statement about the "mystery" of integrated circuits.
So you have no measurements of field coil drivers just your golden ears and personal experience. Yet another subjective thread that went nowhere because it's all conjecture. Like I posted above 99% of the people in here don't have the means or access to field coil drivers so we have to rely upon some proof other than your say so. I can see this is going nowhere as do all subjective posts.
*yawn* so you have NOTHING to show as objective proof and try to make objectivists as being the "bad guys" for asking you to do so?
You laugh at the thought of DBT because the difference "isn't so subtle" and resort to calling an objective approach as "the magic curtain"
You spin a poor argument trying to make objectivity as a religious belief system when in FACT it's subjectivity that calls for such.Get your facts straight.
Then you go on acting all superior due to your ten years of blah blah blah
Telling us to get off our lazy A$$ is such a nice touch considering I ALREADY posted how 99% of the people in here don't have access to a field coil driver let alone two drivers where one hasn't been converted to field coil so we can compare.
Sounds like you just want to come up with excuses as to why you can't show measurements so we should just rely upon your say so
To be honest I found most of your post to be silly considering it's up to YOU the person making the claim to show proof about your statements about field coils. So far I have to give you a big fat ZERO as grade.
Now if you wish to contribute more than "what you heard" I would be willing to discuss this more......otherwise this has become a dead horse.
This fellow does conversions of Altec compression drivers to field coil:
CH Audio Design
On the following page, he shows some before/after measurements and also some work he's done to measure magnetic field modulation by the voice coil signal in a conventional driver.
Field Coil Portal
I can't vouch for the data but it's at least a start.
---Gary
Sorry, I cannot tell you much more on chip, but you can ask true labs.
No secret that when the channel becomes very small, you start having quantum behaviours. Theory of quantum behaviours is not that precise.
I never wrote that I have no measurement and direct experience!
You are wrong. And I never want to be polemic. And I don't like to emphasize my point of view, my results, my my my... Just the contrary of so many people here. I always say: try yourself, don't trust me that much, try.
I listened several FC speakers. And a friend of mine worked on them.
So I can confirm from DIRECT experience that FC sounds better to me. BUT it's not practical and the power supply is so important that probably many DIYers cannot imagine.
A standard PSU gives good results, a top quality low noise one can change it all!
One of my Japanese sensei said me 20 years ago that no one can imagine the difference using a low noise PSU for FC tweeters without trying. He was referring in particular to one FC tweeter made by a Japanese master 30 years ago (I think). He considered that tweeter the best he ever heard. The designer died in a plan crash (Kenji, do you know that tweeter model? I don't remember at all!) and just a few pieces have been done. He also told me that with a good PSU it sounded wonderful. With a low noise stable one, you could understand the difference. I did not try with tweeters.
Right now I want to convert my personal pair of Altec 515. Has anyone here already done it?
Fabio
A few snippets from the Field Coil Portal link......
"however this powerful magnetic field decreases with many factors, age and physical disturbances such as heat, strong vibrations or shocks and to a much less extend to reactions to opposite external magnetic fields, and specially if the magnetic field is disrupted by opening the driver, removing the magnet from the driver just once, will decrease the magnetic field to almost nothing !. such is the case that many if not all Alnico magnets have lost moderate to significant strength in their field , some up to 90% and more!"
I have no problem with that statement, so it seems he is restoring the magnetic strength using a field coil. I wonder how well the driver would perform by simply remagnetising the alnico magnet?
"the magnetic domains must realign again to return to the original magnetic orientation and strength, producing variations in the magnetic field that changes the response of the diaphragm, resulting in induced sound distortions and changes in pitch at it's most extreme excursions"
Who would run a driver to it's most extremes like that?
Also as part of the modification, he includes.
"A pair of brand new all aluminum diaphragms, same as original Altecs in 8, 16 or 24 Ohms. (NO after market here) "
Which makes all measurements on his page a moot point considering just by changing out the diaphragms, the frequency response will be different.
Plus we must remember he is running a business and it isn't just a hobby for him.
I appreciate the links, at least you showed some attempt at giving us something to ponder rather than the subjective tales others on here give us
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Solid scientific measurements showing diagphrams universally wear out would lock the argument.
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