| DKAudio |
| I want to build a driver and am going to start winding my own VC. I will use 24AWG magnet wire (it is the only size I have and I have a lot of it). I am going to use an aluminum beer can for the former and was going to wrap it is Kapton tape. I was wondering what thickness I should use. Also, what glue should I use to hold the VC in place? Could I use polyurethane? I have Minwax fast drying clear gloss polyurethane and clear gloss Minwax Helmsman spar urethane. Would these work? Thanks |
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| Volenti |
| Can't help you with the glues, but remember to put a slit in the aluminum former or it will act as a shorted turn and dump the efficiency in the toilet:smash: |
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| DKAudio |
Hmm, put a slit in the former? Can the ends of the slit touch or can it not touch at all? Thanks for that info, I didn't know that.
That Loctite link was interesting. They make good stuff, pretty pricey too though. I know for bonding the VC to the spider and cone I was told I can use any 5 min epoxy (could probably use that for most of the glueing needs. I didn't see anything for the VC to the former though. |
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| Volenti |
The former is split all the way, there's a pic on this page that shows the gap in the former.
| quote: | | I didn't see anything for the VC to the former though. |
And this is a pretty important, the glue is the first thing that fails when a voice coil overheats. I can see 2 ways of doing this;
1. wind the coil, then use a very thin consistency epoxy that will penetrate the layers to bind everything together.
2. use a very slow setting epoxy and wind the coil "wet", messy but you would be more assured of full glue penetration. |
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| Ron E |
search for a thread called DIY dynamic driver
I posted a spreadsheet to help you predict parameters. |
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| DKAudio |
Thanks for all the information, I appretiate it. Now that I saw that pic of the former I remember seeing the ones I have taken apart like that too. For Kapton tape would this work...
4 Inches Wide x 36 Yards Long x 1 mil Thick
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From C.S. Hyde Co. Product# 18-1S
I will try winding wet with slow drying epoxy. What kind shout I get, from Home Depot would be great. Any other tips with information would be excellent. |
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| bluebeard |
I think most five minute epoxies, even when fully cured, soften considerably under heat. Maybe loctite tech help could give some
assurance on this. May or may not be an issue for you. |
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| DKAudio |
| I'll look into that. What about the Kapton tape? Is there something else that would be cheaper or do I need Kapton? Thanks |
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| tvi |
Most oven bags are made of kapton.
As to adhesives Eminence use a polyimide and Hernon seem to have adhesives for every part of a loudspeaker.
Hope this helps.
Regards
James |
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| Vikash |
If this is just an experimental project, then no, you do not NEED kapton. You're about to increase your daily language expletives if you're going to hand wind a coil ;)
Hardly professional, but this might be of interest: http://www.vikash.info/audio/transducer_design/
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| DKAudio |
| No problem on the winding. I have made a tesla coil before. I wound 24AWG magnet wire on 4" OD PVC for 24" It took long but turned out great. |
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| bluebeard |
Bloomington is certainly large enough to support a couple of adhesive specialty wholesalers/vendors. Look one up in the yellow pages. A couple of years ago I was looking for a particular epoxy type for potting electronics. It was just a one-off experiment, but I needed something with specific
properties - hence, I could hardly deal with really expensive half gallons of the stuff. I explained to a local vendor what I was doing, and they very graciously gave me a sample/trial pac of exactly what I needed. Sounds like your project is similar.
It's not as if they have to worry about bringing a horde of pocket-protected nerds down on their heads for free samples - fortunately, we are relatively few.
There are epoxies specifically formulated for efficient heat transfer (probably critical in your case). There are myriad viscosities available - too high and it wont fill properly; too low and it'll end up a puddle on your workbench. Cure times vary as well and can be used to control flow properties.
If you're lucky, you might run into someone with a great deal of technical knowledge at ye olde adhesive shoppe and a soft spot
for diy'ers. You'll get a sample of just exactly what you need.
Oh hell, this may all just be overwrought, maybe you'll just want to
use mucilage (but then again, you are a man who's winding his own voice coils - and many of us can certainly relate to that) |
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| DKAudio |
| I think polyurethane would work. The only question I have is will it stand the heat? On my tesla coil I brushed it on and it soaked into the layers, I used Helsman after because it is thicker and coated it until you couldn't even feel the wire anymore, it was smooth. It worked great and held everything in place very strong. I tried searching the the temp max but couldn't find anything. |
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| Ron E |
| quote: | Originally posted by DKAudio
I think polyurethane would work. The only question I have is will it stand the heat? On my tesla coil I brushed it on and it soaked into the layers, I used Helsman after because it is thicker and coated it until you couldn't even feel the wire anymore, it was smooth. It worked great and held everything in place very strong. I tried searching the the temp max but couldn't find anything. |
Maybe you could call Minneapolis speaker company and ask?
Or you can experiment and do trial and error. |
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| johnthetweeker |
DKAudio, do you already have the pole pieces/magnet? If you are going to machine the pole pieces it's ok, otherwise you'd have to match the former to the gap available.
I wouldn't suggest the beercan to stay with the coil for ever. Better use a thin sheet of teflon over the can and wind the coil over this, so that the coil can be slipped out after the glue sets. Choice of glue and how neat you can apply it are critical to final result.
Do post your experiences.
Good luck! |
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| DKAudio |
| I thought they used aluminum formers. Where can I get teflon? I don't have anything machined and don't have access to a machine shop. I haven't thought about what I am going to do for the basket, motor structure. I have tons of ceramic doughnut magnets though. |
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| Vikash |
| In which case you probably want to start at a motor structure first, not fit a motor to a VC. First place to start with all this is usually FEMM. |
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| Vikash |
Another mamoth thread, with some very interesting ideas (that sadly never got off the ground) is the DIY Parthenon thread: http://www.diyaudio.com/forums/show...5376&highlight=
Depending on what output you're looking for, it's generally better to consider all the different sections together from the beginning
Don't be put off though, seeing threads like this make me wanna start this all up again... ;) |
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| DKAudio |
I have read every word in the 28 page Parthenon thread. Too bad no one every got around to finishing one. I also would like it to be high excursion; don't need 8-9" though :)
I also have FEMM but haven't done much with it. I opened it a few times and was lost. I am going to have to check examply problems or something.
For the motor I was thinking I could use a bunch of my ceramic doughnuts stacked N to S together. I have some older ceramics that were used inside the voice coil and there was nothing on the outside. Is this design bad? They used to do it a lot but stopped and started surrounding the VC with the magnets and just having the metal pole piece. |
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| johnthetweeker |
Aluminium former will form a shorted link as someone already pointed out. Cutting a slot will again spoil the stiffness. I think professional outfits use a special tool that forms a temporary bobin for winding the coil and the tool retracted and withdrawn after the glue has set. Here in India teflon is available in industrial materials shops.
For high excursion the factors to concentrate on:
(a)The surround and spider should allow the movement: large diameter spider may be required. I have also seen raised spiders in some drivers.
(b)For linearity at high displacement, the length of the coil should be sufficient, so that a part of the coil is inside the magfield at extreme positions.
The idea of magnet inside the voice coil sounds interesting. But remember that the field strength depends on volume of the magnet material. For a given material (ceramic in your case), bigger the magnet, stronger the field.
As for assembly-sequence, I have seen one manufacturer magnetise the magnet after the whole assembly is done. I think it may be difficult to keep the pole pieces in alignment with a strong magnetic field, during the glueing process.
A thought on magnets: have you ever taken an old computer hard-drive apart? They have extremely strong, tiny magnets. I wonder if they can be used in a speaker, because the read/write head in a hard-drive is driven by the voice coil principle. |
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| DKAudio |
| I have many magnets from old HDDs, they are NdFeB. They are pretty small and the field doesn't extend far at all, that's why I thought a lot of my old ceramics would be the way to go. |
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| DKAudio |
| I can get 14GA galvanized sheet metal from work for free, will that be ok for the basket and to transfer flux? I don't want to spend hardly any money because I don't have it right now. I will try an example coil using a beer can aluminum former and Minwax polyurethane to coat the coil. I don't even have enough money to get kapton tape so is there any common household item that will work to go over the former? Single layer of electrical tape? |
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| wolfram |
A friend gave me some pure (99.99) silver wire from some speaker interconnects he had made. With the scrap silver I made a pair for myself and really noticed an improvement in clarity of my audio. Long story short I got to thinking, how could a system wide rewire of silver benefit audio quality?
I have an old pair of Pioneer Dss-9's that I thought would make good candidates for the conversion because the woofers need reconing (have new cones).
If I go to the trouble of rewiring and reconing the speakers, I might as well continue the silver replacement all the way into the speaker itself (IE: voice coil, tinsel wire leads)
I already know I crazy my question is am I insane?
Are there benefits to be had in winding a silver voice coil? |
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| Vikash |
| quote: | Originally posted by wolfram
I already know I crazy my question is am I insane? |
yes. ;) |
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| tvi |
| quote: | | Are there benefits to be had in winding a silver voice coil? |
You might find the following interesting:-
Low TCR wire in high power audio coils
us5664023
Publication date: 1997-09-02
Inventor: BUTTON DOUGLAS J (US)
Applicant: JBL INC (US)
For electric coil windings, particularly in moving coils such as the voice coil of a heavy duty bass loudspeaker or other electro-acoustic transducer, the present invention has found metallic materials, as alternatives to copper or aluminum in the voice coil wire, that can provide increased available maximum SPL (sound pressure level) exceeding an empirical limit, just under 120 dB/1 m, that has been found to apply to various loudspeakers of known art regardless of efficiency and structural differences. Through study of known art regarding this limitation and theoretical analysis of the factors in voice coil structure and design that limit the maximum attainable SPL, a novel basis for selecting voice coil wire material has been developed. By selecting wire material for low TCR (temperature coefficient of resistance) along with suitable resistivity and density, rather than for low resistivity alone which has conventionally dictated copper or aluminum, the present invention has led to the identification of new wire materials that can increase the available SPL. Such materials include alloys of aluminum containing between two and five component basic metals selected from the following group: magnesium, silicon, manganese, zinc and copper. The alloy Al Mg(3.5%) in extruded form yields maximum SPL 1.5 dB above that of pure aluminum and 3.32 dB above that of pure copper.
Regards
James |
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| BassAwdyO |
according to that article there aluminum would be the best pure wire(as far as spl anyway)
I tend to believe as some suggest earlier that the material insulating the coil and glueing it together are more crucial the choosing between copper and aluminium. |
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| wolfram |
2 Q’s
1) Does the former have an effect on the voice coil, for instance does an aluminum former behave differently then a plastic, copper, etc...? My intuition tells me that from an electromagnetic standpoint there must be differences, but are any of these audible?
2) Does anyone know a good software program that would aid in the design process?
I am going to wind my own VC’s for a recone job and I am currently planning or using silver(winding) and aluminum(former) or visa versa(open to suggestions). The former will be insulated with Kapton tape. I am interested in finding out if and how changes in the materials of the VC will effect its performance. |
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