i replaced the coils in my 12 inch kicker L7 i went out today to give them a try and at 40 hertz it took about 4 mins till i had smoke coming out the port in the box.
what looks like has happened is the coil former is made out of paper and the coil actually came off of the former and got all squashed down inside the magnet. i bought these speakers blown up and the stock kicker coil seems to have a coil former made of resin. and the burnt coil i pulled from it was just burnt in 1 spot but still intact. this replacement coil seems to be burnt a little but is like 50 feet long and all unwound.
i saw that kicker (and im asumming others) have speakers that have replaceable motors, and i thought i could do something like this with a set of
L7s. i machined a outer ring for the surround and one for the spider. the only thing is i still need to glue the coil in place. im new to this but im thinking 4 mins is a unusually short lifespan for a speaker. i dont mind replacing these coils i kind of expect to.
for the initial test i ran the speaker with a 40hz tone for 4 mins with a jbl bp1200.1. i realize this amp is over kill but the sub didnt distort or bottom out or complain at all. (till all the smoke, then it just died).
so my questions to the community are.....
1. is it normal to have formers made of this plasticky/paper stuff? or resin or is there even any difference
2. should i go punch this guy in the stomach for selling me an inferior coil or should i buy another one from him? and this time just relax with the 40 hz test
3 does anyone know where to buy reputable coils from?
what looks like has happened is the coil former is made out of paper and the coil actually came off of the former and got all squashed down inside the magnet. i bought these speakers blown up and the stock kicker coil seems to have a coil former made of resin. and the burnt coil i pulled from it was just burnt in 1 spot but still intact. this replacement coil seems to be burnt a little but is like 50 feet long and all unwound.
i saw that kicker (and im asumming others) have speakers that have replaceable motors, and i thought i could do something like this with a set of
L7s. i machined a outer ring for the surround and one for the spider. the only thing is i still need to glue the coil in place. im new to this but im thinking 4 mins is a unusually short lifespan for a speaker. i dont mind replacing these coils i kind of expect to.
for the initial test i ran the speaker with a 40hz tone for 4 mins with a jbl bp1200.1. i realize this amp is over kill but the sub didnt distort or bottom out or complain at all. (till all the smoke, then it just died).
so my questions to the community are.....
1. is it normal to have formers made of this plasticky/paper stuff? or resin or is there even any difference
2. should i go punch this guy in the stomach for selling me an inferior coil or should i buy another one from him? and this time just relax with the 40 hz test
3 does anyone know where to buy reputable coils from?
can anyone recomend a forum where i might get these questions answered?
is this a normal way for a speaker to fail? or do they usually just burn which creates a break/open in the coil?
is there anyway to see this coming so i dont do the same thing a second time?
is this a normal way for a speaker to fail? or do they usually just burn which creates a break/open in the coil?
is there anyway to see this coming so i dont do the same thing a second time?
I'd say 40Hz would be low enough to start warming up coils. If you used it at high power, chances are the coils have cooked that way.
I wouldn't use a paper former in a high powered speaker. If you think about it, the former will act as a heatsink to help pull heat from the coil if it is made of something appropriate. Paper, kapton and aluminum are common. I'd want aluminum for a high-powered sub.
You say that the amplifier is "probably overkill" 😀
Ok, let see if we can figure things out here. 40Hz is probably somewhere near the port tuning frequency of most car subwoofers. You say that the speaker didn't bottom out? Well this is probably due to the fact that the driver was being severely damped by the port at that frequency, so it wouldn't move that much - allowing you to feed it probably more power than it could handle 🙄
As the driver wasn't moving that much a second factor comes into play! If the voice coil isn't moving very much then there isn't going to be a lot of air pumped in & out of the voice coil to cool it - this is the reason you cooked it.
You'll probably find that the voice coil former is made of Kapton, it does look a bit like paper...
Next time be a bit more careful 😀 Music will never generally cause a problem as it's not a pure sinewave test tone...
thanks everyone who responded i am really in need of some answers.
so should i order the same coils that i just blew up?
i had a really hard time finding anyone, anywhere who would sell me coils. i would LOVE LOVE LOVE!!!!! to find coils with aluminum coil formers where do i even start looking for something like that?
how do i know if the former i have now is kapton? (ive enclosed a picture) is kapton the standard or should i even bother looking for something stronger?
the pictures i sent are the old coil and former (the intact one) and the new one you can see that the old coil came right off. can anyone tell if this replacement coil is a lesser quality one?
so should i order the same coils that i just blew up?
i had a really hard time finding anyone, anywhere who would sell me coils. i would LOVE LOVE LOVE!!!!! to find coils with aluminum coil formers where do i even start looking for something like that?
how do i know if the former i have now is kapton? (ive enclosed a picture) is kapton the standard or should i even bother looking for something stronger?
the pictures i sent are the old coil and former (the intact one) and the new one you can see that the old coil came right off. can anyone tell if this replacement coil is a lesser quality one?
Attachments
what is the Purpose of the Paper over the Kapton Former?....to provide a better surface to bond the voice coil on?
yes that is the part that sits inside the spider. if you look closely at the one still in the motor you will see it is barried inside the motor and you can see where the glue is
Something needs to change.
Only you can say if the speaker is underpowered or the amp is overpowered but they're not matched and if you want to play 40Hz again then just buying the same coils will result in the same destruction.
As e-h said, the systems probably OK for music as you don't get 4mins of full on 40Hz but if you're competing for loudness then you need a speaker with greater power handling or maybe go to multiple drivers to split the power.
Only you can say if the speaker is underpowered or the amp is overpowered but they're not matched and if you want to play 40Hz again then just buying the same coils will result in the same destruction.
As e-h said, the systems probably OK for music as you don't get 4mins of full on 40Hz but if you're competing for loudness then you need a speaker with greater power handling or maybe go to multiple drivers to split the power.
Looks like what i said earlier was about bang on 😀
You can plainly see where the poor voice coil overheated the most due to lack of cooling, in fact it looks like it just about managed to burn off the insulation on the wire itself 😱
What you want is a standard coil for the driver, IE a direct replacement for the drive unit in question. I have never replaced a voice coil or re-coned a driver, i didn't know you could actually buy just a voice coil assembly without the cone & spider, outer suspension etc. Replacing them & aligning them is a bit like an art, you need to know exactly what you are doing - if you don't, you're probably wasting your time.
In future if you are going to test things, do it at a frequency where there is a good deal of cone movement for little input. That way you won't overpower the voice coil & you'll get to hear if there is any voice coil scrubbing on the magnet poles. With music you shouldn't have a problem, but as you've found a constant signal with little cooling = 😱
You can plainly see where the poor voice coil overheated the most due to lack of cooling, in fact it looks like it just about managed to burn off the insulation on the wire itself 😱
What you want is a standard coil for the driver, IE a direct replacement for the drive unit in question. I have never replaced a voice coil or re-coned a driver, i didn't know you could actually buy just a voice coil assembly without the cone & spider, outer suspension etc. Replacing them & aligning them is a bit like an art, you need to know exactly what you are doing - if you don't, you're probably wasting your time.
In future if you are going to test things, do it at a frequency where there is a good deal of cone movement for little input. That way you won't overpower the voice coil & you'll get to hear if there is any voice coil scrubbing on the magnet poles. With music you shouldn't have a problem, but as you've found a constant signal with little cooling = 😱
"in fact it looks like it just about managed to burn off the insulation on the wire itself"
yes i did and geez does it ever smell bad.
can you tell if the coil i replaced it with is similar to the one that was in it originally? ie are they both kapton?
i was busy doing tests at home with a sine generator and i was seeing where the port was starting to unload and also doing the finial alignments of the cone but with a only 5A power supply driving the amp i could go down to 15 hz and it seemed just fine. so i figured i would need more power and.... well... see post 1
i for sure for sure WILL NOT be doing the 40hz 1500watt test anymore!! beleive me i have learned something from all of the burnt copper i have been breathing in. but how do i adjust the amp so this wont happen again? can i just put the amp on full and just play normal music? i chose these amps because i didnt want them to get hot and i wanted them to easily handle driving speakers like this. i figured if i used half the power of the amps i would be fine. but during this "test" i just kept turning up the gain and the speakers just kept getting louder. what gives?
yes i did and geez does it ever smell bad.
can you tell if the coil i replaced it with is similar to the one that was in it originally? ie are they both kapton?
i was busy doing tests at home with a sine generator and i was seeing where the port was starting to unload and also doing the finial alignments of the cone but with a only 5A power supply driving the amp i could go down to 15 hz and it seemed just fine. so i figured i would need more power and.... well... see post 1
i for sure for sure WILL NOT be doing the 40hz 1500watt test anymore!! beleive me i have learned something from all of the burnt copper i have been breathing in. but how do i adjust the amp so this wont happen again? can i just put the amp on full and just play normal music? i chose these amps because i didnt want them to get hot and i wanted them to easily handle driving speakers like this. i figured if i used half the power of the amps i would be fine. but during this "test" i just kept turning up the gain and the speakers just kept getting louder. what gives?
Ah...You have just discovered that a speaker can be overpowered without distorting! I'm not sure of the power rating of the driver you have there (the L7), but you'll find it's much easier to get distortion from an underpowered amplifier. That's simply because a smaller amp (than the speaker is rated at) will clip the waveform simply because it can't swing more output voltage. This will make a bit of a racket, a little like feeding the driver a square wave 😉
The simple answer to your question is don't give the driver more power than it can handle with a continuous sine wave! Most drivers will handle a bit of an overload fairly cleanly with music, though tbh i'm not sure about car subs as the driver parameters on every one i have ever measured have been miles out.
Power wise i guess they should be ok, Fs, Qts & Vas always appear to be out by miles, just like they might as well toss a coin & stuff whatever they like on the spec sheet
So, the answer is don't go mad unless playing music. I still wouldn't recommend "turning the amp full" as you have suggested to test a driver if the amp is rated at more than 1.25 X the rating of the driver.
If you want more volume buy another driver & amp & don't turn em up so much 😉
Making a voice coil on an aluminum former, is no big deal, and would sure increase the amount of power the driver can handle.
Magura 🙂
Magura 🙂
Looking at everyones input, I deal with kicker( car audio) those coils a made so cheap, the only way in my lifetime seen one last was in a small sealed enclosure, not to mention , did you spend the time and break in the sub? as well, you showed rubbing on the coils, mis-alighned. the cone is a cartrige and made my people, it could have passed throgh checking, but you really need to lay down paper and clean the magnet, and debris in that motor will detroy the voice coil. I can go on about kicker, they make the best under rated amps, however, Still Water does not make the driver. Speakers are round for a reason.
Get a new cone, turn your amp all the down, break it in which will fuse the coil to the former, and check your voltage @the amp WHILE the car is running.
To me and I have seen that picture so many times,
>low voltage and then clipping,
>never break in a driver @40hz, play it at or around 65-80hz maybe 150. (for at least 48 hrs. not all at once, but you want that coil to bond to the surface of the former, otherwise you will have the same problem.
Get a new cone, turn your amp all the down, break it in which will fuse the coil to the former, and check your voltage @the amp WHILE the car is running.
To me and I have seen that picture so many times,
>low voltage and then clipping,
>never break in a driver @40hz, play it at or around 65-80hz maybe 150. (for at least 48 hrs. not all at once, but you want that coil to bond to the surface of the former, otherwise you will have the same problem.
i have no problem making a aluminum former myself but how to i put on the coil? where do i learn how to do that? ie how much, what size, what density
how do i find out, ACCURATLY how much power a speaker can handle? i have had this question for a long time and its not important in this app but also for all my little speakers aswell. i first started doing this to learn how to fix amps. now i have a mountain of 1-2000 watt amps and i will be using them to drive not only the subs but also the little voice speakers too. i know it sounds funny but i will have a similar jbl bp 1200.1 driving 4x 6.5 inch speakers. if they explode before distorting how the heck am i suppose to know how much amp gain to adjust to the driven speakers?
"might as well toss a coin & stuff whatever they like on the spec sheet "
i agree and it is why i wanted to go and run some horse power through this speaker before taking the accurate TS measurements and doing some accurate modeling. i figured it would change after some use. but now its blown so ill start all over again.
the subs i have are rated at 750 WRMS and the amp has been tested to 1400 WRMS. i have 2 subs and 2 amps. how on earth to find where to adjust the gain on the amp?
is there anyway to monitor the coil in use? ie tempurature or any other indication that it has load on it and is about to fail?
how do i find out, ACCURATLY how much power a speaker can handle? i have had this question for a long time and its not important in this app but also for all my little speakers aswell. i first started doing this to learn how to fix amps. now i have a mountain of 1-2000 watt amps and i will be using them to drive not only the subs but also the little voice speakers too. i know it sounds funny but i will have a similar jbl bp 1200.1 driving 4x 6.5 inch speakers. if they explode before distorting how the heck am i suppose to know how much amp gain to adjust to the driven speakers?
"might as well toss a coin & stuff whatever they like on the spec sheet "
i agree and it is why i wanted to go and run some horse power through this speaker before taking the accurate TS measurements and doing some accurate modeling. i figured it would change after some use. but now its blown so ill start all over again.
the subs i have are rated at 750 WRMS and the amp has been tested to 1400 WRMS. i have 2 subs and 2 amps. how on earth to find where to adjust the gain on the amp?
is there anyway to monitor the coil in use? ie tempurature or any other indication that it has load on it and is about to fail?
another look, kicker sells a coil allignment tool while the glue dries, to "help" it stay linear during excursion. I would call Kicker and inquire about this.
how do you keep the aluminium former round after you have slit it to stop current flowing around the former?
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