You didn't provide any knowledge base, why do you demand something you don't deliver yourself? Oh, wait, yes, you did. You've provided a link to a page where it can be read without sources. Yes, I'm sorry, ofcourse I will provide that too.
Here it is. Voice Coil & Wire facts
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That's correct.
That's correct. For higher impedance fewer windings can be beneficial if you want to keep the inductance lower.
That's plain wrong. The wire of the voice coil is sealed with paint, therefore it doesn't corrode. On the ends it's connected somewhere, there is solder. What's (probably) left free, can corrode on the surface, which then creates a protection layer. That is for oxygen and water. If you add other chemicals, you'd have to worry for the membrane, spider, surround, magnet, pole plates and adhesives first before it becomes relevant.
That might be debatable but I'll leave that topic to other enthusiasts.
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The glass transition temperature (Tg), sometimes referred to as heat distortion limit, is the standard test of a material to retain strength at temperature. It will have one thermal expansion coefficient below that temp, and will be a factor of two to four higher above that temp. Many epoxies bought off a rack or shelf will not list Tg, but the manufacturer's website may list it. Many automotive adhesives are high temp, especially for under the hood use.
For work, I use a wide range of epoxies and adhesives based on requirements such as usage temperature, strength requirements, and radiation resistance.
For room temperature magnets, I will use epoxies which have a higher Tg (117 to about 135 C) for strength; for use in liquid helium or nitrogen I will use an epoxy with a Tg of 45C (such as stycast with 23lv or 24 lv hardeners) so that repairs can be easily made by warming the structure locally to about 50C. Repairs are not practical if the structure requires 120C + temperatures, especially if the structures are a few tons.
Agreed, his coil looks rather pristine. That is why I suspected simple failure caused by lack of sufficient adhesive.
Other than your "high temp is not needed", good advice. That said, we both agree that his coil did not see high temp, so your statement may indeed be sufficient for his driver.
In general, drivers will have both excursion and thermal limits, so I always recommend higher temp materials.
Agreed, it was interesting, thank you Max.
iCG: remember who the article's target audience is. I would have written it at about that level for general audiences as well. I can only go hard core in writing tech for articles that have a very small audience worldwide, like maybe five or six people. So pinging an ele mag for keeping it general is of no value.
As I recall, copper pricing was swinging wildly back in that article timeframe (2012). We took a factor of four hit on what we bought, and that was because we were not ready to buy two years earlier.
As max mentioned, lower mass. The copper is there for solderability.
There is an electrical conductivity hit, and thermally it is half as good as copper.
One item not mentioned is thermal expansion, copper is 16.6 and alum 25.5. The Manu may have to increase the gap OD to accommodate increased expansion, and that costs in magnet. I've repaired clad alum vc's back in the early 80's, but do not like it. Nor do I like vc's done with bare aluminum, as soldering them is a "beach". And I'm very good at soldering.
john
Actually, terminal corrosion can be different for clad aluminum wire. It's diffusivity is higher, and the manufacturer or tech may use stronger flux or more heat to overcome the difficulty.
That is not applicable to the rest of the speaker components.
Your statement of impedance got scrambled. It looked like you said for higher impedance..fewer windings. I suspect you meant the opposite.
John
Ps. You've put me in unfamiliar territory here....I am agreeing with Max...😉
That is not applicable to the rest of the speaker components.
Your statement of impedance got scrambled. It looked like you said for higher impedance..fewer windings. I suspect you meant the opposite.
John
Ps. You've put me in unfamiliar territory here....I am agreeing with Max...😉
Simp2005: it is also possible that the edge of the coil was nicked during manufacturing. Inspect all the wire on the edge of the wind for that or abrasion. Also, if the basket were deformed during final box assembly, it could have forced rubbing (I suspect you would have heard that however.)
If the wire was not bonded well, the loose portion of the wire may have significant cyclic fatigue damage. This might be visible through the enamel of the wire, but may not. I recommend you not re-use any of the wire that was loose, but go back half turn on each end, do the repair on the opposite side of the failure.
John
If the wire was not bonded well, the loose portion of the wire may have significant cyclic fatigue damage. This might be visible through the enamel of the wire, but may not. I recommend you not re-use any of the wire that was loose, but go back half turn on each end, do the repair on the opposite side of the failure.
John
Thank you and I agree on most. The lowest Tg I've found was at 135° though, for this repair it'd still claim it to be sufficient because of the condition of the VC and since easy use is for first-timers much more important than most other. For other drivers and situations I'll ofcourse agree.
Yes, absolutely! Especally on PA equipment, CAR drivers and home cinema subwoofers I would almost always use the most safe solution. It's often tied to the use though. On these drivers there comes the mechanical limit first. If subwoofers are added, then the limit will be the distortion. Aaaand if that's exceeded, it's purely intentional damage. 🙄 😀
You have a point there. Sorry. I've just seen already a few 'look at this page, if it's somewhere on the internet, it's a fact' too much. Especally if the page then does not even cites any sources I'm getting critical. And you have to admit, it was 'advertised' as the solution on adhesives.
Maybe it hit you later than europe? I remember mid 2000s I felt so cheated when I bought loudspeaker cables and realized too late it wasn't copper and therefore completely unusable for me (often changed pa setup, flexibility).
The copper also lowers transitionally the initially tearing of the aluminium surface, so it is actually also a structural component of the wire aswell. (well, ofcourse not for a VC though)
Yes, ofcourse. Wider air-gap means less motor strength which has to be compensated by stronger magnets. To talk about saving at the wrong end, CCAW VCs of cheap chinese neodym PA sub drivers died very often of heat problems - bad ventilation, low magnet 'heatsink' and ever rising power claims caused a lot of driver-deaths. I'm partially glad the neo price rose that much because meanwhile you generally get better designed and produced drivers all over the world and not 'everything' has to be neo.
Oh yes! I know a song of that! 😀 The problem at CCAW VC repairs is, sometimes you have to deal with bare aluminium because the copper has been scratched off by the defect or by the removal of the insulation of the wire. And not everywhere you can simply pull down one winding to fix it (in and outwards + edge wound vc or air motion transformer diaphragm).
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Emerson and Cuming stycast 2850 specifies three different hardeners for use, 9, 11, and 23/24lv. The lv is room temp cure with Tg at 45C (over two decades the data sheets have bounced back and forth between 33C, 65, and 45C. It' been stable over the last decade at 45C. They use it in other formulations as well. The best part is it reduces the mix viscosity an order of magnitude, but useful room pot life is about half an hour.
Not sure, time is rolling past too fast, especially the last two years. Vendors were setting quotes as valid for two weeks only. I am curious now, I'll have to check my build documentation to see when I was designing the cable tray system.
I could see that, but I suspect in general they went thin copper for cost and weight. Not sure how the drawing process would harden the copper though. I use copper over niobium titanium so the process tends to harden the copper more than it would aluminum due to the toughness of the NiTi.
John
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