Field Coil vs Ferrite Magnet sound

Hi All,
Ever since I started fiddling with FR speakers, I've been reading on how good FC FR sounds
& this has gotten me very curious. Like SET Amps, FC speakers are also from yesteryears.
Yes I understand the principals of how FC works & their flexibility in the adjustment of magnectic
strenght which offcourse would affect it sound production. My question is what if we adjust the
magnetic strenght of the FC to equal that of a same speaker but with Ferrite magnet instead, will
the FC still sound better & if so would it be due to coil design etc ?
By going FC this opens another can of worms which I've read the PS is very important to SQ as well,
so what is the proper type of PS is used to attain optimum results assuming that FC speakers are low voltage
version.

Many thanks
 
It would probably need a constant current source, similar in principle to LED drivers but well executed.

I had this crazy idea to integrate a field coil driver with a S.E. class-A amplifier, where the output transistor splits the phase of the audio signal between the voice coil and the field coil. It would probably be terrible due to the asymmetry, but you never know if you never try.
 
Now that might be a handfull to implement abstract but kudos to think out of the box.
Speaking of Shunt Current PS read this : https://theaudiofeast.com/field-coil-psu, so which is which ?
Would be great for guys whose experimented with PS to share their thoughts & experiences.
Pointless to buy an FC & yet not getting optimum sound if PS is not done right. For my diy
builds I always focus lots on optimizing PS to try & achieve good sound hence I do believe that PS for FC
will definately affect sq of the driver.

Many thanks again
 
Somewhere I read that yesteryear designs used the FC as a filter choke, which seems like a recipe for hum and noise unless some kind of feed-forward noise cancellation was intended - although efficient on use of power supply current. So, a dedicated quiet supply is already a significant improvement. It's possible that some hum-bucking designs were available which might be a good idea even with dedicated supply.
 
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some hum-bucking designs were available
They were:

HB.jpg


https://www.antiqueradios.com/forums/viewtopic.php?f=6&t=234041

Hugo
 
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I saw them in old radios, many moons ago. Saw the many wires on the speakers but as a kid, little did I know they were for the field coil. I didn't even know how speakers worked. Then I started turning all the pots I could find until the radio lost all life. :)

Sorry to sidetrack the thread...

Hugo
 
Hi All,
Ever since I started fiddling with FR speakers, I've been reading on how good FC FR sounds
& this has gotten me very curious. Like SET Amps, FC speakers are also from yesteryears.
Yes I understand the principals of how FC works & their flexibility in the adjustment of magnectic
strenght which offcourse would affect it sound production. My question is what if we adjust the
magnetic strenght of the FC to equal
that of a same speaker but with Ferrite magnet instead, will
the FC still sound better & if so would it be due to coil design etc ?
Then they will sound exactly the same.
The voice coil, which is an electric motor (literally!!!) pushing a mechanical load (the cone + air) has no clue as to how the magnetic field crossing its turns at 90 degrees comes from or how it´s created, all it "knows" is its intensity.

This very clear illustration from none less than Mabuchi Motors,who should know ;)

electromagnetic-forces_im01.gif


The general Physics classroom "memory rule" is Fleming´s "left hand rule":
electromagnetic-forces_im02.gif
, same thing.

Again:voice coil (and speaker) does not know Alnico from Ceramic from Neodymium from Fieldcoil.

That said, field coil is infinitely adjustable so it can perfectly mimic any of the others plus it can reach impressively high flux density (magnetic strength); problem being it´s the most complex and expensive Technology.

In the 80´s, together with some partners ($$$$$), we made about a dozen 30" speakers, trying to capture the Disco Club market, which was in full swing.

REAL wall/roof/floor shakers, only way to get the proper magnetic field to drive the monster 6" voice coils was to use field coils, no commercially available Ferrite ring would do, "donut" holes could hold 4" coils, tops.

A sonic success, an abysmal commercial failure, nobody could/would actually buy them, so Plan B was to rent them for special events.
Couldn´t even recover invested money, let alone "earn" someting.
 
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When I ordered my Sonido field coils I had a discussion with Zen Mod about the topic of power supply.

His recommendation was a well executed CCS.

After reviewing the CCS circuit of the power supply being offered by Sonido he gave it a pass, so I went with that.

My only issue is that I can hear some humming coming from the small encapsulated transformer of the power supply if I am standing closer to it…especially when I’m using the highest current setting.

At some point I’d like to try a higher VA toroid to see if I can get rid of that.
 
Same magnetic field strength should mean the same sound out of otherwise identical speakers. But the field coil,can get turned up to 11! You get a widely adjustable driver using the ps to tune it to the use at hand. That being said it’s a lot of stuff to manage and get right. If you like an adventure give it a try. What’s the worst that could happen?
 
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hb-jpg.1187166


Got one of those downstairs.

Execution.

Given that it is WAY more expensive to build a FC (and the supply), usually all efforts are made to not cut corners so these are premium drivers and most of what they are being compared to is much less costly and not directly comparable.

A FC does allow you to play with the T/S (leaving the box designer with more degrees of freedome to deal with).

dave
 
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Many thanks again Dave. Actually I am looking into Ems LB8 ferrite or FC don't even know
if they're really good. What worries me is the PS for FC, seems like it matters lots & this will
end up being another variable of getting really good sound. Sigh.

Thank you again
 
I have owned Altec Lansing 416-8b with alnico magnet 416-8c with ferrite magnet sound is exactly the same absolutely no different. Years back a company called decware tried to scam people selling field coil conversions of a Dayton 8" full range the Dayton were under $100 each the Decware version were like $1200 each and if you power the FC to have the same gause they sound exactly alike. A lot of people try to scam / steal same guys Decware are trying to sell Lii audio full range 15" open baffle for like $3500 the speakers are $500 from lii audio free shipping the coast of the baffle DIY a couple hundred. At 51 years of age I have heard more ******** from the audio world commercial & DIY than I have heard from our politicians !!!! If field coils really sounded better then you would see them for sale in the commercial world and people in the DIY world would be converting their own speakers to field coils. It is ancient technology the only reason it ever existed was because permanent magnets were not available at the time once permanent magnets were available field coil disappeared faster than carburetors. The appeal of field coil speakers is always with the guys that have full range speakers with tube amps witch to me says one thing and one thing only these guys are more into old gear the age and or era of things than they are into the sound that's cool these things should be appreciated and preserved.
 
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I have owned Altec Lansing 416-8b with alnico magnet 416-8c with ferrite magnet sound is exactly the same absolutely no different. Years back a company called decware tried to scam people selling field coil conversions of a Dayton 8" full range the Dayton were under $100 each the Decware version were like $1200 each and if you power the FC to have the same gause they sound exactly alike. A lot of people try to scam / steal same guys Decware are trying to sell Lii audio full range 15" open baffle for like $3500 the speakers are $500 from lii audio free shipping the coast of the baffle DIY a couple hundred. At 51 years of age I have heard more ******** from the audio world commercial & DIY than I have heard from our politicians !!!! If field coils really sounded better then you would see them for sale in the commercial world and people in the DIY world would be converting their own speakers to field coils. It is ancient technology the only reason it ever existed was because permanent magnets were not available at the time once permanent magnets were available field coil disappeared faster than carburetors. The appeal of field coil speakers is always with the guys that have full range speakers with tube amps witch to me says one thing and one thing only these guys are more into old gear the age and or era of things than they are into the sound that's cool these things should be appreciated and preserved.

Did you try modding the ferrite to make it adjustable? I stand by my free idea above about adding a field adjustment knob next to the signal gain knob.