In fairness to Decware, as Dave says, it wasn't a scam. Steve didn't disguise the fact that it is / was a modified Dayton, and ignoring the verbiage, it was an application of the old transformer-coupling to alter the driver behaviour & make it suitable for [particularly] his hybrid OB designs. Not a bad idea really. A bit expensive, but then, it's a low-volume hand-built product and Decware is a business that needs to turn a profit, not a charity. So while the presentation was a bit OTT 😉 at the time, it's hard to criticise too much. Steve styled it to look like a FC -but if you want the transformer in close proximity to the rest of the motor, sticking it in a can on the back is more or less mandatory, since there isn't much option in the matter. And since nobody claimed it was a field coil, if anybody bought it without checking, they couldn't exactly complain that it wasn't.
Eminence madeand sold an adjustable field ferrite speaker and it wlorked as promised.
Only problem is that it being a passive device, yu cpuld only turn field down , not of much use to us in the Hi Fi world.
It filled a niche in the Guitar world by providing an adjustable reduced sensitiviy speaker (down up to -9dB) to avoid "honey"/neighbours/police trouble waway.
that was a neat variable Q solution by Eminence.
Decware I believe used their "Gizmo" scheme on a mod FR. I tried it with a 6.3vct transformer. Put a 1K pot's legs across the 120v winding of a filament transformer. The low Z secondary winding goes in series with the speaker. Damping and other effects are on the fly and the results are interesting. A cap could be put across the pot for other response alterations.
Decware I believe used their "Gizmo" scheme on a mod FR. I tried it with a 6.3vct transformer. Put a 1K pot's legs across the 120v winding of a filament transformer. The low Z secondary winding goes in series with the speaker. Damping and other effects are on the fly and the results are interesting. A cap could be put across the pot for other response alterations.
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Gents if I may, permamnent magnet motors are already a very mature in design
but I still read things like Feastrex Naturflux or EMS HPMF ll, what makes them
different from the norm ?
Thanks
but I still read things like Feastrex Naturflux or EMS HPMF ll, what makes them
different from the norm ?
Thanks
currently available are this drivers from Supravox in both magnet versions (FC vs. Alnico)
1) 215-EXC mk2
https://www.supravox.fr/en/products/215-exc-mk2-haut-parleur-large-bande-70w-93-a-102db-6-ohms
2) 215-2000 mk2
https://www.supravox.fr/en/products/215-2000-mk2-haut-parleur-large-bande-20w-98-5db-6-ohms
Diaphragm (cone) and basket seems to be the same - thus any sound differences can therefore only be caused by the differences in the magnet versions.
Maybe one of the member have heard this in a comparable test.
check out also this threads
https://www.diyaudio.com/community/threads/supravox-165-2000.326720/
https://www.diyaudio.com/community/threads/supravox-reviews-215-exc-or-sig.20035/
https://www.diyaudio.com/community/threads/field-coil-driver-for-ob-design-advice-sought.336142/
https://www.diyaudio.com/community/threads/question-to-supravox-fertin-field-coil-users.50306/
https://www.diyaudio.com/community/threads/field-coil-alpair-12.176065/
https://www.diyaudio.com/community/threads/supravox-215-exc-ob-and-400exc.216364/
https://www.diyaudio.com/community/threads/thoughts-on-supravox-215-2000-exc-or-phy-hp.138105/
https://www.diyaudio.com/community/threads/supravox-165-alnico-vs-exc-on-a-ob.321786/
https://www.diyaudio.com/community/threads/field-coil-power-supply.346814/
1) 215-EXC mk2
https://www.supravox.fr/en/products/215-exc-mk2-haut-parleur-large-bande-70w-93-a-102db-6-ohms
2) 215-2000 mk2
https://www.supravox.fr/en/products/215-2000-mk2-haut-parleur-large-bande-20w-98-5db-6-ohms
Diaphragm (cone) and basket seems to be the same - thus any sound differences can therefore only be caused by the differences in the magnet versions.
Maybe one of the member have heard this in a comparable test.
check out also this threads
https://www.diyaudio.com/community/threads/supravox-165-2000.326720/
https://www.diyaudio.com/community/threads/supravox-reviews-215-exc-or-sig.20035/
https://www.diyaudio.com/community/threads/field-coil-driver-for-ob-design-advice-sought.336142/
https://www.diyaudio.com/community/threads/question-to-supravox-fertin-field-coil-users.50306/
https://www.diyaudio.com/community/threads/field-coil-alpair-12.176065/
https://www.diyaudio.com/community/threads/supravox-215-exc-ob-and-400exc.216364/
https://www.diyaudio.com/community/threads/thoughts-on-supravox-215-2000-exc-or-phy-hp.138105/
https://www.diyaudio.com/community/threads/supravox-165-alnico-vs-exc-on-a-ob.321786/
https://www.diyaudio.com/community/threads/field-coil-power-supply.346814/
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Field coils are useful when the magnetic field has to dynamically alter it's intensity over time. Like in a voice coil, or in the field coils of a MRI or a LHC. Modulating the current will modulate the strength of the magnetic field.
Now what is the benefit of a field coil when the aim is to generate a constant magnetic field? I hardly see any usefulness. Instead, in this use, there is a needless waste of ressources because of the need of the constant supply of current. So you loose both in an economical, and also in an ecological logic.
The only advantage might be the satisfaction of having set up a vintage design by yourself. DIYaudio. This motivation seems vey ok, indeed.
Now what is the benefit of a field coil when the aim is to generate a constant magnetic field? I hardly see any usefulness. Instead, in this use, there is a needless waste of ressources because of the need of the constant supply of current. So you loose both in an economical, and also in an ecological logic.
The only advantage might be the satisfaction of having set up a vintage design by yourself. DIYaudio. This motivation seems vey ok, indeed.
a reference (in general - don't know about F's 0.25% magnetic distortion)
https://www.klippel.de/fileadmin/kl...linearities_Causes,Parameters,Symptoms_06.pdf
https://www.klippel.de/fileadmin/kl...linearities_Causes,Parameters,Symptoms_06.pdf
Since neither company is especially forthcoming about what either marketing term ('Naturflux' or 'High Precision Magnetic Field') means, I'd be inclined to conclude 'nothing'. IIRC the former has curved rather than straight returns, which isn't common but AFAIK has been done by others, while I can't find anything on the latter suggesting it's just a phrase cooked up to sound impressive. Which in engineering terms, it doesn't, particularly. I'm not criticising per se -we're living in that sort of age. Just don't take what's claimed too seriously if it doesn't seem to have much basis.
We can all do it:
I could go on, but I won't, you'll be relieved to see. 😉
This would indicate commercial viability at least, the way they were used as power supply filter chokes shows this.
Oh, it's viable, it's flexible, & even if you set everything else aside, it's technically 'better' in that you have a level of adjustability not available with permanent magnet designs. It does come at a cost though -financial and wading through some of the high-fantasy writing that's often applied to them, justifiably or not.
Is anybody here able to calculate a viable design e.g. for replacement of a modern magnetic neodym structure such as found either in an 1-inch tweeter and also in a 12 inch woofer? Target result would be the field strength within the voice coil's magnetic gap which should be the same in both types of assembly, e.g. neodyn v.s. field coil.
And then, also calculate the power requirement of these two hypothetical field coil assemblies? I mean power requirement in terms of watt such as P = I^2 * R, where I is the current trough the coil, and R is the copper wire resistance? You may calculate with an iron core providing a relative permeability or n=5000.
I tried to do so, but I did not succeed. I really would be interested so see some numerically computed results.
And then, also calculate the power requirement of these two hypothetical field coil assemblies? I mean power requirement in terms of watt such as P = I^2 * R, where I is the current trough the coil, and R is the copper wire resistance? You may calculate with an iron core providing a relative permeability or n=5000.
I tried to do so, but I did not succeed. I really would be interested so see some numerically computed results.
That's a tough one. I'd start by looking at application notes for ferrite cores for SMPS chokes, or maybe an online calculator that lets you plug in the numbers. The cross-sectional area and thickness of the air gap will probably be a critical factor in the whole design, guiding you to figuring out the thickness and length of the iron loop, and how many turns of copper x current you need to generate the field.
There could also be some prior work on here.
There could also be some prior work on here.
A more succinct way of what i said earlier… even if a FC is better, would the money put into it be better spent elsewhere.
The speaker is the face of our hifi, but one must not forget that it is no better than what you feed it.
dave
If you somehow manage to integrate it into a class-A amplifier as a choke (thinking of the output transistor as splitting the phase between the voice coil and the field coil), then it's for 'free'.
Field coil, AlNiCo magnet or ferrite magnet - either way, the pole piece works in saturation. The only difference could be in the length of the voice coil, for increasing Xmax. That would need a different spider and surround design, though.
I read somewhere that there is a physical reason fo the AlNiCo magnet being long, while the ferrite magnet being flat, but I forgot. Many swear on AlNiCo for some reason. Probably a field coil is even better than AlNiCo? But if the pole piece is saturated, it should no be.
I read somewhere that there is a physical reason fo the AlNiCo magnet being long, while the ferrite magnet being flat, but I forgot. Many swear on AlNiCo for some reason. Probably a field coil is even better than AlNiCo? But if the pole piece is saturated, it should no be.
What it seems online and what it is in reality are not the same. It's easy and not worth worrying about . Think of shopping for expensive shoes and worrying about the laces.
An off the shelf (or appropriate diy version) linear bench dc supply with adjustable voltage and current in the ranges the drivers can use will be fine. The adjustability is especially useful in the beginning for fine tuning to the enclosure and ear. Once you have what you want you can switch to a better supply (bought or built) with fixed output if you want .
Assuming you're thinking stereo, wire the two field coils in series and they act as chokes for each other. (This of course necessitates twice the voltage at the same current.) Add another choke somewhere in there for more CCS like behaviour if you find it helps.
Really, the supply should not be part of your decision of what driver to use (buy), unless of course electrical power availability has some limiting factor where you are. Then permanent magnet might be the answer.
by "mod" I meant the addition of the transformer "Gizmo" - (I'd like to find similar to that one at a low price) - doing similar with a filament fransformer was fun with my Heresy I's as a twirl of the 1K pot could range from fairy tight bass to loose "tube-amp bass" using a Crwown class D amp.. I did not get to check its effect upon T-S parameters but did post a number of TrueRTA response graphs of the circuit. (now lost)
Yes!
And for perseveration's sake: At what cost in terms of dissipated watts does this saturation come in the case of a field coil, e.g. for a tweeter and/or for a woofer?
I stand corrected it was not a field coil in my own defense I did read about them back in 2011 But I will stick to Decware being a scam sorry that is just how I see it. Paying an extra $1000 for a transformer and a metal cover that's a little extreme 50% of the cost must be paid before shipping and no returns !!! Sorry but reputable business except returns. Decware even say they hand build these in the USA witch is false the drivers are made in communist china and modified by Decware in the USA the use of deception to sell a product is immoral If someone outside the DIY speaker world reads hand built in the USA they are going to believe it and that is anti American to say the least don't use this country's good name to try to make a buck it's anti patriotic and immoral. As far as the measurements are concerned they can't justify a $1000 cost difference. Sorry if I sound negative toward Decware but I feel a need to protect American consumers from questionable business practices. And like I said i am sorry for sounding negative but we are living in a time where people and businesses have no integrity and it's time for the real America the people of this great country to stand up and fight the good fight no matter how large or small the issue and if honesty does not start to prevail this great country is going to go down the toilet. https://www.decware.com/newsite/FRX.html
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