A donut for the first one who find the title's reference... 😀
ok so, while testing (torturing) the PA woofer-mid, It started to smell burnt voice coil. A lot.
Now, I'm not used to smell that a lot since usually, when I torture drivers, it's JL audio's subwoofers, and they don't have that kind of heating v.c. problems...
so I have a question: is it the driver that goes into his first heat cycle (so it's somewhat normal) OR the driver may be damaged or lost some of his original properties in a permanent way?
In other words: HOW BAD are the consequences of a voice coil that got very hot, but still working apparently normally...?
ok so, while testing (torturing) the PA woofer-mid, It started to smell burnt voice coil. A lot.
Now, I'm not used to smell that a lot since usually, when I torture drivers, it's JL audio's subwoofers, and they don't have that kind of heating v.c. problems...
so I have a question: is it the driver that goes into his first heat cycle (so it's somewhat normal) OR the driver may be damaged or lost some of his original properties in a permanent way?
In other words: HOW BAD are the consequences of a voice coil that got very hot, but still working apparently normally...?
Apocalypse Now

Yesss. Apocalypse Now, exactly.
Strawberry or chocolate ?
In other words: HOW BAD are the consequences of a voice coil that got very hot, but still working apparently normally...?
The first time, for a few seconds ... probably not that bad.
But each time you repeat it will just make it worse until you finally kill it.
You might want to do it and your ears a favour and turn down the volume... rather a lot. 😀
The first time, for a few seconds ... probably not that bad.
But each time you repeat it will just make it worse until you finally kill it.
You might want to do it and your ears a favour and turn down the volume... rather a lot. 😀
So, if I understand correctly, it is cumulative. Heating the coil once, then a second time, then a third time, causes cumulative damage. I thought, a little naively perhaps, that if the first heating had not killed the coil, once completely cooled, it would work `` like a new one '', unless of course pushing it again, and possibly too far.
But it is cumulative... ?
Here is an older thread...
https://www.diyaudio.com/forums/multi-way/328755-burnt-voice-coil-smell-lingers.html#post5574554
So.. testing resistance or inductance would be the solution to verify a smelly driver?
https://www.diyaudio.com/forums/multi-way/328755-burnt-voice-coil-smell-lingers.html#post5574554
So.. testing resistance or inductance would be the solution to verify a smelly driver?
I'm on this thread to hopefully learn something. I think we could reasonably speculate on the effect of a shorted turn as your link suggests.So.. testing resistance or inductance would be the solution to verify a smelly driver?
What about when the coil warps, not enough to rub or to short a turn?
But it is cumulative.
Yes it is. Every time it gets hot it sheds small amounts of the insulation and weakens the wire until one day it turns itself into a fuse and goes pop. Then it's done.
I also see you said the coil is aluminium ... aluminium melts at a lower temperature than copper, so keep that in mind.
Now, if you take the advice and keep it reasonable, it will probably go another few years for you. But if you keep overheating it, a few more times and it will be dead.
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So.. testing resistance or inductance would be the solution to verify a smelly driver?
Not necessarily. What happens with aluminium coils that are usually packed in an epoxy type of material is that the wire softens and thin spots form inside the epoxy insulation. The thin spots will act as thinner wire, which can handle less current. It might not be enough to show up on an ohmmeter for quite some time... usually not until it's ready to blow.
The other thing that can happen is that repeatedly heating the epoxy coating causes it to shed small flakes of epoxy, which look like bubbles on the coil, then it's only a matter of time until one of them gets into the right spot to jam your speaker. When the coil doesn't move it loses cooling and poof, it burns.
I've also seen speakers get hot enough to melt the metal formers they're wound on. These usually rub for a while and you can hear that by pressing the cone in with your fingers (very carefully). When that happens it's on it's last legs as well because the friction only increases the heat on the coil.
Forgive my curiosity ... but just how loud are you playing this thing?
This reminds me of an alloy cylinder head. Overheating on one occasion can cause a minor degradation in performance, but the warpage and performance may stay consistent until another overheating event.I also see you said the coil is aluminium ... aluminium melts at a lower temperature than copper, so keep that in mind.
The overheating make the glue smell (200 c° ?) & melt.
The temperature also change the spl shape theorically (impedance curve?) by creating a smooth large notch of few db... you may or not percieve cause the room is ruling the sound at bass frequencies.
but the most iportant effect maybe your thymphan melt into the crowd what you may want to avoid.
how are insulated voice coil wires ? high temp ceramic ? Is a short circuit possible with a break due to the heat ?
Edit : on a movie perspective, what about the organ notes of the Close Encounters of the Third Kind...
The temperature also change the spl shape theorically (impedance curve?) by creating a smooth large notch of few db... you may or not percieve cause the room is ruling the sound at bass frequencies.
but the most iportant effect maybe your thymphan melt into the crowd what you may want to avoid.
how are insulated voice coil wires ? high temp ceramic ? Is a short circuit possible with a break due to the heat ?
Edit : on a movie perspective, what about the organ notes of the Close Encounters of the Third Kind...
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The smell is the enamel insulation on the wire or the glue holding it to the former off gassing or burning. Polyurethane is a common insulator for magnet wire. Epoxy is a common glue for bonding the magnet wire to a former, and for bonding turns of wires to each other so they don't unravel. Both polyurethane and epoxy are thermosetting polymers so they don't 'melt' per se, but above 100-200*C will soften and then burn. The more severely you burn the insulation on your coil wire, the more likely bits off insulation are to flake/chip off the wire, producing a short between 2 or more turns which will both affect the performance of the driver and potentially harm your amplifier by exposing it to an unusually low impedance. The more severely you burn the adhesive, the more likely turns of wire will come loose from the former, causing the wire to rub in the gap.
It is possible to get the coil hot enough to produce a faint smell (off-gassing of the polymers) without permanently damaging the insulation or glue, but a noticeable smell - especially a burning one - is not normal for any driver and continuing that type of abuse will definitely lead to a failed driver long term.
It is possible to get the coil hot enough to produce a faint smell (off-gassing of the polymers) without permanently damaging the insulation or glue, but a noticeable smell - especially a burning one - is not normal for any driver and continuing that type of abuse will definitely lead to a failed driver long term.
Sounds like a myth to me. The melting points of aluminium and copper are 660*C and 1083*C respectively, so by that point the polymers are most definitely completely burnt off by the heat and the coil will unravel inside the motor... therefore it makes no difference the type of metal used in the wire. One thing to note is that if the insulation is burnt off the wire, it may only generate a short intermittently while the coil is in motion and the turns vibrate together, so a static impedance measurement may not show a problem. The place where a speaker coil most commonly fails open circuit is where the coil is soldered to the tinsel leads as solder melts around 180-220*C - again a failure here may be intermittent with vibration.Not necessarily. What happens with aluminium coils that are usually packed in an epoxy type of material is that the wire softens and thin spots form inside the epoxy insulation.
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This is nonsense. You can't see if voicecoils fail due to "to much power, to much amp's, clipping, clean or dirty power".
The reason all electronics fails is heat. Voice coil wire fails due to much peak power. Which makes the coil itself overheat/burn. The assembly fails due to much continues power which heats the whole thing up and melts the glue.
Short and long term power compression are the result of short and long term heat.
A positive thing of this is that the increased temperature raises the voice coil impedance, limiting current and thus power and heat. Just don't make up for it with a 'little' more power. Doubling power will give +3dB minus extra power compression. So maybe 2dB, hardly noticeable but enough for a great smell. 🙂
Why Do Tweeters Blow When Amplifiers Distort?
Power Handling Vs. Efficiency
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TMM, yu wasted my day ! My ref loudspeaker is only 84 db efficienty with small speakers... hungry in watts... I know have the feeling to look at a dead alive movie when looking at it now...
. Me going right now at Wallmart to purchase an ice bucket whatever for the ice cubes to cool the voice coil or to prevent the glue to waste my oak parquet... and a baseball bat if the loudspeaker rebirth to life witl melted eyes and want to jup on me !

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Not necessarily. What happens with aluminium coils that are usually packed in an epoxy type of material is that the wire softens and thin spots form inside the epoxy insulation. The thin spots will act as thinner wire, which can handle less current. It might not be enough to show up on an ohmmeter for quite some time... usually not until it's ready to blow.
The other thing that can happen is that repeatedly heating the epoxy coating causes it to shed small flakes of epoxy, which look like bubbles on the coil, then it's only a matter of time until one of them gets into the right spot to jam your speaker. When the coil doesn't move it loses cooling and poof, it burns.
I've also seen speakers get hot enough to melt the metal formers they're wound on. These usually rub for a while and you can hear that by pressing the cone in with your fingers (very carefully). When that happens it's on it's last legs as well because the friction only increases the heat on the coil.
Forgive my curiosity ... but just how loud are you playing this thing?
I'm pushing the driver intentionally. I wanted to reach the limit, but I was simply surprised to reach thermal limit before mechanical limit, especially on such a driver.
So it's a FaitalPro 12pr320 (AES power handling 300w) on a ICEpower 700as2 amplifier that delivers 350w @ 8 ohms. So I was theoretically exceeding the rated power handling by a bit but I was not monitoring on my wattmeter. Will do next time.
Was playing pure tones from 25-70hz for about 3-4 minutes, temperature raised very quickly (dustcap was hot) and it started to smell burnt vc in less than 30 seconds of these tests. I continued anyway, since I was ready to witness a total failure of the driver, but he never failed. Just got very hot and smelly.
To answer your question, I had a SPL reading on my calibrated RTA of 123,2db @ 1m distance (in-room) @ 61hz. Also 111db @ 31hz.
So, yes, I know very well that is not normal use. I was just curious about the voice coil per se. It's really not the first time in my life that I burn a coil but it's sure the first time that I witness a driver that is still working after such a smelly episode...
This is nonsense. You can't see if voicecoils fail due to "to much power, to much amp's, clipping, clean or dirty power".
The reason all electronics fails is heat. Voice coil wire fails due to much peak power. Which makes the coil itself overheat/burn. The assembly fails due to much continues power which heats the whole thing up and melts the glue.
Short and long term power compression are the result of short and long term heat.
A positive thing of this is that the increased temperature raises the voice coil impedance, limiting current and thus power and heat. Just don't make up for it with a 'little' more power. Doubling power will give +3dB minus extra power compression. So maybe 2dB, hardly noticeable but enough for a great smell. 🙂
Why Do Tweeters Blow When Amplifiers Distort?
Power Handling Vs. Efficiency
Thank you for the input, Think.
I lost about 2db because of the power compression at one point. But that's hardly a surprise... I could probably cook an egg on the neo magnet...
but the most important effect maybe your thymphan melt into the crowd what you may want to avoid.
Haha!
No worries.
Actually did SPL drag racings in the 90's... Anything below 130db is ''nothing'' in the first two octaves. Starts to be (very) painful above, though.
Was able to sustain 158db @ 55hz for few minutes without problem. And I got my hearing checked twice since. It's fine. 😉
Edit : on a movie perspective, what about the organ notes of the Close Encounters of the Third Kind...
Oh? Just bought the vinyl 🙂
Didnt know that soundtrack was having ultra low frequencies... 16hz organ ?
but unfortunately, the 12pr320 even with the passive rad, it's not a driver to go much under 26-27hz... Limited xmax + 42hz Fs
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