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Rewinding loudspeaker coil

Or admiration of the art of louspeaker making.

46V DC on 8 ohm 10 inch speaker, didn't last long, going o/c. Decided to try rewinding as I've never tried it before. Found a clean way to remove the cone from the frame. Desoldered the braid connections. Heating the frame with a hot air gun and pushing the periphery of the cone with a well used and rounded wooden kitchen spatula, separated cleanly from the gummy glue. Put in spacers to stretch the inner dust diaphragm and hot air gun heating unglued the periphery of that corrugated disc. I didn't expect to see what was inside. A burnt mass of wire and the innermost end of the penetrating lacquered paper cylinder neatly burnt off in a perfect ring. Gap in magnet about 66 thou, paper cylinder about 5 thou thick and 2 layers of about 2 x 30 turns of 6 thou wire (originally). I don't fancy trying to rewind on a small paper cylinder and fixing to the remnant all with such XY&Z precision to clear that 2x 25thou slot gap in the magnet. For the next time anyone know of a WWW site explaining the jigs, paper lacqering process, wattage/wire guage/turns etc ?. Its amazing such cloth and paper art, more than technology, can take the punishment.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
n cook
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Not a task I would try, although I believe some have done it.

If the speaker manufacturer is reputable/well known you may be able to buy a replacement cone/voice coil assembly. This is the standard method used by speaker repairers and it is so much simpler and can be very cost effective. The next solution is to buy a new driver.....

Reply to
Ross Herbert

n cook spake thus:

Possibly impertinent question: wouldn't a guy want to use a mandrel of some kind to wind the coil on? That way you wouldn't have to worry about a flimsy paper cylinder collapsing, no? (Like maybe a turned piece of wood.)

--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
Reply to
David Nebenzahl

way to

Heating

a

heating

off

layers

to

wood.)

But the cylinder is just glued to the cone, take it off any mandrel and there is nothing to stop it going just slightly oval. Temperature changes, humidity changes, self weight in use etc and I only come across a coil/cylinder rubbing in the magnet housing after abuse.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
n cook

You might have some luck by posting this over in rec.antiques.radio+phono. I believe that some folks there have rewound a voice coil.

Bill ~~~~~~~~~~~~~~~~~~~`

n cook wrote:

Reply to
Bill Jeffrey

n cook spake thus:

OK, then how about lacquering the assembly after winding; shouldn't this help it keep its shape? I think this is what speaker mfrs. do.

--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
Reply to
David Nebenzahl

only

I've been doing some measuring and looks as though such speakers use a sort of air bearing/ ground effect. Inside diameter of the slot in the magnet something a bit less than 1.502 in so probably 1.5 inches. Inside diameter of the paper cylinder that goes inside the magnet gap about 1.65 inches so with a gap width of bit greater than 66 thou and paper plus double thickness coil of 15 thou means the wire cannot touch the outer diameter of the magnet gap. And I just cannot believe that in all operational circumstances that the inside of the paper cylinder can never touch the inside surface of the slot with only 7 thou of clearance. A silicone treatment to the inside surface of the paper cylinder would make sense, anyone know whether it is used ? Knowing that I might have a go gluing a new bit of cylinder and new coil to the existing remnant of cylinder as there is plenty of external room for excess glue/binding.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
n cook

Your going to have to insert shims in there anyway to reattach the cone so its linned up. I don't know if ferro fluid is silicone based, probably.

greg

Reply to
GregS

If you wind the coil with a mandrel inside of the paper cylinder, and bond the coil to the cylinder with something ( adhesive? laquer? polyurethane?) when you're done, I would think that the wire would add significant rigidity to the otherwise flimsy paper.

If you're still worried about deformation, leave the mandrel in the coil while you glue the cylinder to the cone. Then there is no way it will go out of round, short of gross mechanical injury.

Just a thought.

Pete

Reply to
H. P. Friedrichs

Hi...

Used to do this way back in the olden days (just shortly after they invented sunshine :) so let me throw in my 2 cents in the hope it may be helpful.

First, though, never ever created voice coils themselves. On a rare occasion replaced one. Much more often replaced cones that had been penetrated by little fingers, tools, or just dried out and cracked.

A thought, if I may? Don't think I'd glue the winding to the form; might rather consider shellacing it in place, while the whole thing is still on it's solid form. Use a spray can; that way you'll stiffen the paper form as well.

Don't think it matters much (if at all) if the form does go slightly out of round while it's "in hand" What has to be done is find pieces of paper that will fit perfectly between the magnet and the newly wound coil and it's form. Has to be just right - tight enough to firmly hold the coil in place, yet able to be pulled out without damaging the coil or form. (remember that the coil has to not only be centered, but also temporarily hold the coil at the proper height - so that it won't hit bottom or come free of the magnetic field when the cone moves)

So, experiment with paper weights, find ones that can fit just snuggly enough. Cut yourself a number of pieces, 'bout 3 or

4 inches long, 1/4 inch wide. Drop the coil in alone, look with a flashlight and magnifying glass to see what it looks like bottomed. Take it out again, insert it with the paper shims all around so that half of the free space you just saw is now free again with the shims in place.

Now glue down the outer circumference of the cone, and spot glue the voice coil to the cone at 4 equidistant spots between the shims. When this glue is firmly set, remove 4 more shims at 90 degree seperation, tack the newly freed spots. Keep this up until the shims are all out, and the coil is firmly held all around its perimeter.

Install the dust cap, and you're done :)

Take care.

Ken

Reply to
Ken Weitzel

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