Field Coils Anyone?

[Mr. Widget]

I was recently made aware of the new flagship Grande Utopia EM from Focal/JM Lab... Steve Schell should love the woofers at least. Sorry Steve no horns, but they claim to have been able to increase the sensitivity of these 16" woofers to 97dB /m and maintain a very low system resonance by using a massive electro magnet instead of a permanent mag. Sounds very interesting:

http://www.grande-utopia-em.com/en/technologies/em.php


Widget
.

[Guido]

Bl = 34 Tm !
Wow!

[scott fitlin]

Heres comes the NEXT craze, FIELD COILS!

I heard a pair of field coil speakers, old W.E., They do have a unique sound.

EVERYTHING OLD IS NEW AGAIN, and IMPROVED!

:D

[Mr. Widget]

Bl = 34 Tm !
Wow!Exactly!


Widget

[Jan Daugaard]

It gets really interesting when such woofers are made available as components and not just as a part of a complete system such as the Grande Utopia.

Does anybody know of modern field coil woofers that are available as components?

[Hoerninger]

Just for curiosity, how much power is needed to engage a field coil, I ask for an example?
___________
Peter

[Mr. Widget]

It gets really interesting when such woofers are made available as components and not just as a part of a complete system such as the Grande Utopia.Sure, but don't count on it.

However, if it works as well as they claim, perhaps other manufacturers will build some for us crazy DIY types.


Widget

[spkrman57]

Just for curiosity, how much power is needed to engage a field coil, I ask for an example?
___________
Peter


With a variable power supple (PS) for the field coil the parameters (T/S) can be changed due to the different BL factor.

The amount of current flowing through the field coil will accomplish that.

Steve SCHELL can elaborate much better than me on that though!

I don't remember what voltage/current parameters are usually common.

Regards, Ron

[scott fitlin]

It gets really interesting when such woofers are made available as components and not just as a part of a complete system such as the Grande Utopia.

Does anybody know of modern field coil woofers that are available as components?www.supravox.com.

They offer Field Coil, Permanent magnet in Alnico, also a silver wire VC as yet another option.

PRICEY, though!

[pos]

With a variable power supple (PS) for the field coil the parameters (T/S) can be changed due to the different BL factor.

The amount of current flowing through the field coil will accomplish that.

Steve SCHELL can elaborate much better than me on that though!

I don't remember what voltage/current parameters are usually common.

Regards, Ron
something in the ballpark of 10V (variable) and 5A

here you can see the T/S for different voltages:
http://www.supravox.fr/haut_parleurs/400_2000_EXC.htm

[Hoerninger]

... 10V (variable) and 5A

Thank you, Pos!
When going class A the extra amount of about 50 W per speaker is relativ small. ;)
____________
Peter

[pos]

Plus you don't have to let it turned on all day long!

And with powered speakers you can even get rid of these nasty little 9V batteries in your cc networks :D

[scorpio]

www.supravox.com (http://www.supravox.com).

They offer Field Coil, Permanent magnet in Alnico, also a silver wire VC as yet another option.

PRICEY, though!

Besides Supravox, Fertin is another excellent French brand of Field Coil speakers, just as pricey as the Supravox...

http://www.fertin-acoustic.com

Cheers

[scorpio]

Plus you don't have to let it turned on all day long!



Mmh, I don't have the review around anymore, but this statement does not seem to hold true, Fertin Field Coilers are reported to take a couple of hours after being 'energized' to sound good, they are reported as flat and boring when cold.

I have no personal experience of that though, beyond having heard well run-in and warm Supravox ones (they were amazing...)

[Jan Daugaard]

There is a caveat about the BL factor: We don't know the DC resistance of the voice coil in the Grance Utopia woofer, and -- all other things being equal -- the BL factor increases with the square root of the DC resistance of the voice coil. A 16 ohm woofer will thus -- all other things being equal -- have twice the BL factor of a 4 ohm woofer.

[Ducatista47]

Just a heads up about an older thread than has some good information about field coil drivers. It is pretty good if you pay special attention to Steve Schell's posts and ignore my own ignorant drivel.

I wish I could delete about half of my old posts... I wouldn't blame 4313B if he feels the figure should be more like 97%. The more I learn the less I like a lot of what I used to write. And I am still learning.

At this rate I will end up not liking anything I ever wrote. ;)

http://audioheritage.org/vbulletin/showthread.php?t=12274

Clark

[brutal]

Heres comes the NEXT craze, FIELD COILS!

I heard a pair of field coil speakers, old W.E., They do have a unique sound.

EVERYTHING OLD IS NEW AGAIN, and IMPROVED!

:D

I think you're onto something. Ad for 288 to 287 conversion.

http://cgi.ebay.com/Altec-288-Driver-Field-Coil-Conversion-287-284-HFdriver_W0QQitemZ290272597320QQihZ019QQcategoryZ7 3372QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://www.ch-audio.com/Photos/CH288287-2.jpg

[4313B]

At this rate I will end up not liking anything I ever wrote. ;):rotfl: Join the club. I hate 110% of everything I ever posted and would scrub it all in a heartbeat. Don repeatedly says no though.

I think this Focal driver is pretty cool but don't lose sight of the fact that it is just another toy. :)

[Mr. Widget]

I think this Focal driver is pretty cool but don't lose sight of the fact that it is just another toy. :)Tool or toy? That is a distinction where the line gets pretty blurry.

I have been very impressed with Focal's Utopia line in the past. Assuming they didn't "f" this one up, I bet it is pretty impressive.


Widget

[4313B]

Tool or toy? That is a distinction where the line gets pretty blurry.Toy.

A tool would be something like a Stradivarius.

[Mr. Widget]

A tool would be something like a Stradivarius.Ah, but in who's hands? ...and I don't think a Stradivarius would make a very good hammer.


Widget

[speakerdave]

Ah, but in who's hands? ...and I don't think a Stradivarius would make a very good hammer.


Widget


Maybe, but it could conceivably be converted into a hammer dulcimer.

[Mr. Widget]

Maybe, but it could conceivably be converted into a hammer dulcimer.Ah geez... we have really drifted here. :)

I guess this is where the thread initiator gets ticked off... oh wait, he's one of the biggest Off Topic offenders. :banghead:


Widget

[Hoerninger]

Back on topic, what the heck makes a field coil driver so expensive? :dont-know
The alnico/ferrit/neodym is replaced by simple copper, what makes the difference? :screwy:
__________
Peter

[Mr. Widget]

Interesting question... in the case of this Focal driver they are using 7Kg of copper, but I doubt that others use anywhere near that much.

It must be the extra set of binding posts.;)


Widget

[SEAWOLF97]

I was recently made aware of the new flagship Grande Utopia EM from Focal/JM Lab..
.

http://www.audioheritage.org/vbulletin/showthread.php?t=22191

[Mr. Widget]

Yeah, but it was hearing about the field coil woofer that piqued my interest... ;)

From that photo and the ones I had seen in the mags, it just looked like Focal was chasing Wilson toward the ugliest speaker honors.


Widget

[timc]

Bl = 34 Tm !
Wow!


Check this out: http://www.bcspeakers.com/index.php?sez=1&categoria=2&id_descrizione=44&prodotto=201&id_descrizione_prod=38



I could start in the demolission buisness with a couple of thoose.


-Tim

[Chas]

:rotfl: Join the club. I hate 110% of everything I ever posted and would scrub it all in a heartbeat. :)

Dream on, Dood....positive or negative, it's some of the best content here. :)

[Jan Daugaard]

I just saw that a Grande Utopia costs 65.000 euro in Germany, which without 19% German VAT is the equivalent of approx. $70.000 each.

[Ian Mackenzie]

Just a heads up about an older thread than has some good information about field coil drivers. It is pretty good if you pay special attention to Steve Schell's posts and ignore my own ignorant drivel.

I wish I could delete about half of my old posts... I wouldn't blame 4313B if he feels the figure should be more like 97%. The more I learn the less I like a lot of what I used to write. And I am still learning.

At this rate I will end up not liking anything I ever wrote. ;)

http://audioheritage.org/vbulletin/showthread.php?t=12274

Clark

Your killing me..

Clark..don't sell yourself short.

We're Tomb Raiders and visited the JBL Tomb like Indiana Jones..and washed the dust down with a few fine ales. Where was Lara Croft?

In my book seeing is doing in this business

[Ian Mackenzie]

I heard some Utopia's recently and was disappointed....

I think the Feastrex field coil would be interesting but like $6500+ a pair .........of course that is cheap compare to the Cognet drivers.

[Ducatista47]

We're Tomb Raiders and visited the JBL Tomb like Indiana Jones..and washed the dust down with a few fine ales. Where was Lara Croft?

In my book seeing is doing in this business
That tomb held no field coils, but it was full of cyclopean sarcophagi, each disguised as a 43XX. Entombed within each was the sound of the heavens. Upon opening the door to the inner sanctum beyond - which looked much as a laundry room would - we beheld boxed JBL drivers truly beyond number... Hidden in the uppermost level of the structure was a device diabolical enough to crush any unwary intruder. Many tons of vintage SAE, with only puny wood beams and flooring to hinder their earthward plunge.

We escaped the tomb unscathed but carried off nary a farthing's worth of the vast treasure within. We did leave with something far more valuable, memories of revelries, sonic and alcoholic, with the keeper of the tomb. And in the forge, the keeper shared the secrets of his black art, revealing the magic he employs to craft the sarcophagi. There was no sign of Lara, but the keeper's wife was most fair to behold, and generous of spirit. I recall, as if through a haze, how we were all generous of spirits - and heady brews.

Clark

[Steve Schell]

Wow, a three page field coil thread and I had missed it until Widget PMed me (thank you). I had to smile when I first saw the ad in Stereophile for the JM Labs speaker with the field coil woofer. Okay, that's one driver down and how many to go? True enthusiasts don't stop until all the drivers are slurping DC. JM's ad copy makes it sounds like they are the first folks since Bell Labs to think of using an electromagnet, which is a surprise to those of us who have been hip deep in them for many years now.

Audio technology has been a very strange trip all along. Joe Roberts in Sound Practices reprinted an old article written by Robert Fulton in which he portrayed the entire history of audio as pretty much a downward spiral from the beginning. At first equipment was developed by brilliant minds to solve difficult problems such as filling a 2,000 set theatre with sound using a five watt 1920s amplifier. They did it! Then as things went along other considerations intruded: manufacturing cost, serviceability, shipping weight, on and on, most of the resulting design decisions tending to erode rather than improve performance per se when taking the long view looking back.

As I've plunged deeper into audio over the years, the technologies my ears have led me to all seem to be rooted in the 1920s and 1930s, and were mostly discarded by the 1940s. Directly heated triodes, battery biasing, transformer coupling, field coil drivers, large horns all allow me to connect with the music in a way that I find uniquely satisfying, yet they were all gone from the mainstream before I was born.

I have been predicting a field coil renaissance for quite a while now. There are constant stirrings, though world domination still seems a ways off. To this point it has mostly been an underground thing, those who have taken the time to fire up the surviving prewar drivers and experience their fine performance. Being energized by a field coil doesn't automatically make a speaker great, it just tends to make it better. That's enough for me.

Although it strikes me as progress for a "high end" speaker company to be touting field coils, IMO Focal still has a way to go in their thinking. They state in Widget's link that to go low the cone mass has to increase, which lowers efficiency, which requires a field coil motor to get the efficiency back up. For a horn loaded guy like me, this is all backwards. The way I look at it, to trace the delicate audio signal most perfectly the cone mass must be minimized and the motor must be maximized. Then the driver is placed in a horn that provides adequate loading for the response desired, and ideally puts the driver resonant frequency up somewhere in the passband where it is largely swamped and damped out by the heavy horn loading. In this condition the driver can efficiently follow the audio signal without constantly fighting with its self-resonance. This philosophy of course tends to result in some pretty huge horn speakers, every spouse's dream.