But that much of curing time with standard adhesive doesnt help in double layers and 4 layer winding.Outer layers start to intrude into the bottom layers as tension builds up making the process unreliableIt's standard 2 component industrial "slow" epoxy.
Mixed life, say, 30 minutes, hardening time: 8 to 16 hours unless you use an oven, which is recommended because it becomes more liquid and "wets the surfaces it touches.
As an example: if I let it harden at room temperature, everything is fine, but if I unwind a couple turms, the wire keeps its enamel.
But if I oven cure it, it's much harder to unwind and it becomes bare shiny copper wire, the epoxy strips the enamel.
Ps: I am talking about hand winding and manual machine winding for amateur purpose..
Don't worry, I handwound many VC in the beginning and still do with prototypes or the odd non standard repair.
Believe it or not *there is* a proper tension which both allows the wire to be properly applied but not disturb the one below.
At least it works with 2 layer ones for sure; should work with 4 layers with more care.
Remember that the first one is wound with higher tension, the second one with a lighter one and so on.
The beauty of the precoated adhesive wire is that epoxy is dry, with only just-activated surface tacking, but even in that case it gets some thermal curing ... and wire does not slip.
Good luck.
Believe it or not *there is* a proper tension which both allows the wire to be properly applied but not disturb the one below.
At least it works with 2 layer ones for sure; should work with 4 layers with more care.
Remember that the first one is wound with higher tension, the second one with a lighter one and so on.
The beauty of the precoated adhesive wire is that epoxy is dry, with only just-activated surface tacking, but even in that case it gets some thermal curing ... and wire does not slip.
Good luck.
I only ever made one voice coil for a a speaker. An 18" speaker with a 3" voice coil that originally had aluminum windings. I just wanted to see if I could repair this speaker. I bought .004" thick aluminum from McMaster Carr. Built the coil form and used JB weld epoxy to adhere the wire to the former. I was surprised to see that the coil "floated" in the magnetic gap (trial fit before attaching cone) I then realized that JB weld has FINE STEEL PARTICLES in it! I figured all my time was wasted! I completely assembled the speaker anyway. To make a long story short, the speaker seemed to work very well! I used it in an out door horn system for my bass horn. It worked great all year. The speaker sat outside for months and always seemed to work very well. I designed the speaker to be weatherproof with a protective sealed door to keep out spiders and critters when not in use. There is a picture of the system in the introductions section.
Here is what I am using to bond virtually anything with anything on speakers:
4 Minute Epoxy Steel (C1-54) - China Epoxy Steel,Epoxy Steel Products
Actually it is not Epoxy, but a 2 component acrylic glue (super glue) with a syrup-like consistence. It is incredibly strong, cures fast (you have about 2-3 minutes to apply it), fills up to 1mm gaps, heat resistant, and workable very well after cured (1/2 hour).
Drawback: it stinks like hell until cures. In my country it sells for about 2 USD/pack, but I think you can buy it anywhere in the world. Once I put together a magnet assembly with this, then tried to take it apart when I discovered that the air gap was offset. Finally the ferrite magnet broke apart, but the glue remained intact, so strong it is. As usual, it does NOT bond to PP and other Polyolefines, but to everything else it is your best bet.
4 Minute Epoxy Steel (C1-54) - China Epoxy Steel,Epoxy Steel Products
Actually it is not Epoxy, but a 2 component acrylic glue (super glue) with a syrup-like consistence. It is incredibly strong, cures fast (you have about 2-3 minutes to apply it), fills up to 1mm gaps, heat resistant, and workable very well after cured (1/2 hour).
Drawback: it stinks like hell until cures. In my country it sells for about 2 USD/pack, but I think you can buy it anywhere in the world. Once I put together a magnet assembly with this, then tried to take it apart when I discovered that the air gap was offset. Finally the ferrite magnet broke apart, but the glue remained intact, so strong it is. As usual, it does NOT bond to PP and other Polyolefines, but to everything else it is your best bet.
Why does Aluminium foil float in magnetic gap ? to be precise it falls into the gap as if there is viscous force inside .Aluminium is paramagnet if I am not wrong ?
Due to the floating charecteristic I shifted to Kapton.
ButI am still curious to know why,surprisingly the Aluminium foils of original manufacturer don't float.
Due to the floating charecteristic I shifted to Kapton.
ButI am still curious to know why,surprisingly the Aluminium foils of original manufacturer don't float.
No, it is the current induced by the magnet assembly in the aluminum cylinder which creates a magnetic field opposite to that of the magnetic field of the motor assembly. This acts as a brake.
The manufacturer probably made a slit in the aluminum cylinder to prevent this from happening. Still, eddy currents will be created in any aluminum or other conductive VC former, which is why non-conducting VC-formers create less distortion than conducting ones. In principle, Kapton or fibre glass are therefore to be preferred, but they have less thermal handling capability. Like everything in drivers, there is a trade off.
The manufacturer probably made a slit in the aluminum cylinder to prevent this from happening. Still, eddy currents will be created in any aluminum or other conductive VC former, which is why non-conducting VC-formers create less distortion than conducting ones. In principle, Kapton or fibre glass are therefore to be preferred, but they have less thermal handling capability. Like everything in drivers, there is a trade off.
Yes, even with a slit the aluminum is damped.
As of why use different form materials?
The speaker *does* sound different, it's not an audiophool myth like many others but can be easily duplicated and measured.
I make speakers with all former materials, as an example my 12" Guitar speaker
can be made , using exact same frame, cone and magnets; same VC turns but different former and adhesives, into 3 very different flavours:
Aluminum + thick/heavy epoxy: 80W rms. General purpose but relatively "midrangey", not great bass because it's self damped (what you describe) and no top highs, because coil + adhesive are heavy.
Yet it's the strongest, so best for replacement purposes, where the customer burnt the original one.
Kapton + lighter epoxy: 50W RMS Most general purpose from the acoustic point of view, today it's the most popular solution.
Paper + thin wire + lacquer (transparent nail enamel) adhesive. Lightest, flimsiest construction, 20W RMS, but the classic "Vintage" sound found in Millions of records sincenthe 50's.
*Very* sensitive, perfect for brilliant Strats and Teles, to play Country/Blues/Funky, etc.
As of why use different form materials?
The speaker *does* sound different, it's not an audiophool myth like many others but can be easily duplicated and measured.
I make speakers with all former materials, as an example my 12" Guitar speaker
can be made , using exact same frame, cone and magnets; same VC turns but different former and adhesives, into 3 very different flavours:
Aluminum + thick/heavy epoxy: 80W rms. General purpose but relatively "midrangey", not great bass because it's self damped (what you describe) and no top highs, because coil + adhesive are heavy.
Yet it's the strongest, so best for replacement purposes, where the customer burnt the original one.
Kapton + lighter epoxy: 50W RMS Most general purpose from the acoustic point of view, today it's the most popular solution.
Paper + thin wire + lacquer (transparent nail enamel
) adhesive. Lightest, flimsiest construction, 20W RMS, but the classic "Vintage" sound found in Millions of records sincenthe 50's.*Very* sensitive, perfect for brilliant Strats and Teles, to play Country/Blues/Funky, etc.
The Coils I wind do have slits. I have checked them against the original manufacturer coils many times with different ones, mysteriously my coils only show this field problems.
I believe manufacture do some kind of treatment to thier metal formers or they use somekind of alloy mixture to handle this issue. where as mine is pure aluminuim foil bought from hardware shop.
Hope you might have noticed many premium dome tweetors and drivers from Vifa and similar manufacturer comes with aluminium VC formers to this date.
Good thing I like about aluminum VC is thier heat dissipiation capability.
Honestly,I love the high efficiency and broader frequency range of paper former VC drivers.
I have wound many paper coils using leatheroid paper (brown paper used for insulating trafo).they sound brilliant.
Best one I have made is paper former underhung VC,Nothing can beat it with rear horn loaded.
I have wound many paper coils using leatheroid paper (brown paper used for insulating trafo).they sound brilliant.
Best one I have made is paper former underhung VC,Nothing can beat it with rear horn loaded.
I made a "3" inch voice coil for an 18" bass driver for a large outdoor horn. My aluminum former was aluminum, with a slit(gap) (original former was non-metal-fiberglass? with edge wound aluminum coil) I wound two layers of copper wire. I unthinkingly used JB weld to adhere the coil to the former. my coil floated in the magnetic gap because there are steel particles in the JB weld! I figured this was a waste of time. This was an experiment to see if I could successfully make and install a voice coil in a blown speaker and if it didn't work I had another speaker on hand. The repaired speaker works VERY well for me. (I use it from 22 to 150 Hz) Its been in use for two years and still sounds great. Also I store it outdoors in an unheated shed for the winter. BTW, I worked with large high flux density magnets at work. If you passed a piece of aluminum in front of the poles, eddy currents produced in the piece of aluminum make the aluminum seem like you are moving it through a thick syrup. ONLY when the aluminum is moved. Aluminum will not float in a magnetic field like my steel based epoxy voice coil did. It may fall (move) slower than when not in a magnetic field due to the eddy currents. For my low frequency use, the steel in the JB weld does not seem to audibly degrade the speaker's performance.
Thanks Ray,
Eddy current sounds real reason behind it. Because with or without coil Aluminium foil does move like in a syrup.But I would also like to know how did manufacturers original coil don't show this phenomenon ?
I have few 2 layer and 4 layer voice coil which had to be removed due to damaged cones, they all simply fall into magnet gap .
If you still have access to the "aluminum" former that does not "float" in the magnetic gap, put an ohm meter across two accessible points on the former material to see if it actually conducts electricity. I'm wondering if possibly the former material is actually a silvered (mirrored) mylar or Kapton that makes it look like aluminum. The only other thing I can think of is that the magnetic gap was not strong enough to make the "syrupy" action noticeable.
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