^^^^^that.
Not peak but RMS, by definition.
RMS power exactly refers to "thermal/heating" power.
Huge short peaks are not that bad, because some voice coils, specially cheesy car subwoofer types, have a lot of thermal mass and will integrate a short peak into a not-that-bad average, but continuous power will heat it up bit by bit until it overheats and fails.
Weakest link is adhesive, usually Epoxy, which way before actually burning loses a lot of mechanical strength, starts cracking first and then crumbling or flaking.
Wouldn´t be *that* bad, except that a voice coil + magnet is literally an electric motor, vibrating and pushing a heavy cone back and forth.
That huge mechanical force tends to crack adhesive and "disassemble" voice coil.
It can also bubble , not usually Epoxy itself but tiny air bubbles trapped in the adhesive or between coils when winding.
Yes. Not actually *melt* because Epoxy is thermosetting, but above 130C to 180C most Epoxies become weak and brittle and then mechanical forces tear coil apart.
At higher temperatures, of course, it carbonizes and burns.
For comparison, wire enamel , Class F or H, the kind usef for winding electric motors so "stronger", both thermally and mechanically that "transformer grade" wire, is *guaranteed* full mechanical strength under great vibration and rotational speed (hint: electric *motor* insides) up to 165 or 185C .
FWIW I make my own Guitar speakers (which are abused by definition) and only use such wire, plus high temperature Industrial Epoxy.
IF wire enamel was improperly chosen , it may flake or chip off wire and stick to Epoxy, but tht is not very common.
Then comes former material:
* Paper : weakest of all, cellulose starts browning and cracking above (sustained) 100C but even at 90C it already dehydrates a lot and becomes rigid-but-easy-to-crack.
* Nomex: by itself it stands a lot of temperature, say 150C and evn 200C for some time, big defect is it´s "calendered", pressed between two highly polished HOT rollers. Very smooth surface but it traps a lot of air which easily bubbles when overheated. Bubbles are irreversible and scratch polepiece making speaker unusable.
* Kapton: won´t "burn" until above 400C but sadly melts and deforms at quite lower temperature, say 250 or 300C, depending also on mechanical stress.
It´s VERY common to see twisted wretched Kapton coils.
* Aluminum: no way to burn or melt it, all other VC elements will catastrophically fail way below that point.
The video is nonsense, and poster is making blanket assumptions based on "samples of one".
Voice coil does not know or care about amp nationality, that´s ridiculous.
The Brazilian amp charred that VC a lot, simply because it put out more watts (Volts and Amperes) into it than others, period.
"Holes in a VC former" come again from extreme heating, *some* point will fail before others; if anything it´s a VC problem , not amp brand or Country.
No, he can NOT tell which amplifier was used (or which Country it came from) just by looking at the VC.
Unless owner tells him, that is, which is what happened here.
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Ok, thank you very much, I get it now.
So, bottomline, the bottleneck here in the whole design is the polymers (glue), not the metals (coil). So basically, the best solution to adress these problems would be to use the best and most advanced polymer that can withstand both high temp and repeated heat cycles (long term stability, so it doesnt crack or get weaker over time), am I right?
Frankly, what bugs me the most is not the outright possible failure, it's rather the ''cumulative'' thing, that can lead to sudden failure when the driver is not pushed hard...
Ok thank you for the explanation, it makes sense to me.
So basically, the cumulative damage is directly related to the epoxy losing his original properties in a permanent way?
@JMFahey; Thx, for your additions and correction that epoxy burns instead of melts when it heats up and loses its strength.
What about a wire (voicecoil) failing, we don't agree.
If I say that the voicecoils will fail at a power peak and the higher the average (RMS) power is, the hotter the coil already is and it will fail at a lower power peak then when it would be cold(er), then we might agree. 🙂
What about a wire (voicecoil) failing, we don't agree.
If I say that the voicecoils will fail at a power peak and the higher the average (RMS) power is, the hotter the coil already is and it will fail at a lower power peak then when it would be cold(er), then we might agree. 🙂
also, is the aluminum or copper REALLY need to reach the melting point for the V.C. to fail, structurally?
FWIW, I thought I read that the Ohm Walsh driver used aluminum wire insulated with an oxide and the VC temperature could operate at 400 C indefinitely w/o damage.
IF fact, lost technology?
IF fact, lost technology?
I once drove a car whose rear-view mirror was glued to the windscreen, and it would fall off and I'd attach it with epoxy. On a hot day it would eventually soften and fall off again.
42 hz is ok for most musics... not enough for movies ? I don't know, I'm not even sure with all those Dolby things than we can come close with a vynil or a simple compact disc !
The ref to the film was not about low hz but the loudspeakers that play loud to communicate with aliens... the famous momentwhen they play organ notes is apealing but nothings t see with the copters of Apocalypse Now 😀
want low bass : some rare organs comes lower than 16 hz : 4 hz to 8 hz ! so can not enter in the compact disc format and anyway you can just hear the harmonics...😱 .asking myself if not dangerous for the heart btw !
True.
That oxide is actually heavy anodizing to ensure a thick layer.
And being "glass", it melts at a higher temperature than Aluminum itself (that´s one of the reasons it´s so difficult to solder aluminum, even with a blowtorch).
Insulating anodization is currently used when needed, not sure about the adhesive used though.
At least recognize this guy's fortune teller's credentials by claiming he can even see if it was Korean power or Brazilian power that blew your woofer....