Got this diagnosis back from an damaged 15" Eminence speaker recently. What might cause a voice coil to come unwound? I got covered under warranty so I'm guessing its not user damage(?)
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Voice Coil "unwind"
- Thread starter ErnieD
- Start date
Depends but generally speaking I thought they epoxied the windings after winding with a varnish or something similar. My geuss would be distortion of the voice coil former in the speaker itself of overtempature cuasing the voice coil to fail loose bond and unwind.
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
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- Owner, Bill Fitzmaurice Loudspeaker Design
Excess heat build up in the voice coil can melt the epoxy bond. Combined with some slap of the coil against the backplate from overpowering and unwinding would be the result. You're lucky they covered it. I'd consider adding another cab to handle the power you're using, assuming the cab that it's in isn't a defective design, which also can result in blown drivers.
it happened last year with my 4 month old NV215 cab and Jim said he gave me the benefit of the doubt and sent out a new driver. So I used this cab in a moderate volume, small nite club, soul/r&b band, with PA support. Never any pop or slap and I set my amp flat cept for alot of low&hi mids, I've never used so little bass tone before. Since I was thru the PA, the mids help me cut thru nice on stage, with 
a rather quiet drummer and guitarist for a change. I've never played with so little volume before.
Well I placed the cab in my livingroom last nite to be sure it and all cords, basses, batteries, etc were working well for my gig tonite and I heard that raspy sound out of the top speaker again, and at very low volume. I tried other basses, amps, cables, checked batteries, etc and it still sounded bad. The more I turned up the volume and with each note I plucked, it was like hearing the glue gradually seperating, to my ears. So Jim is sending out another driver but he said I may get billed if Eminence finds I damaged the driver. I guess if its the same cause as the the last one, I will take the hit this time. I had thought of just buying a new Deltalite 2015 or Kappa 3015 to drop in the cab instead. But dont know if that would fit with the NV cabs tuning. Guess I'll drop the new driver in and wait to see what they find.
But I must reiterate, I've never played thru a cab so softly as I have thru this cab. I use 2 GB Neox 212T's in my other band where I get no PA support. I usually use my GK1001RBI with the NV cab, 540 watts @ 4 ohms. And I have used my B1500 with it, stand alone, but it was set all flat, cept mids boosted a touch. And used my Peavey Cirrus 5 flat and the bass knob backed off, this bass has a very mid-heavey tone. So I can't see where I am causing the damage but I understand it could be possible. I've always used ported cabs and maybe this sealed cab is not for me, can't really say.
I've been vasilating over selling/trading the NV for a ported 410, guess its time to consider this again, but I'll play it again wth the new driver at one more gig to be sure.
a rather quiet drummer and guitarist for a change. I've never played with so little volume before.Well I placed the cab in my livingroom last nite to be sure it and all cords, basses, batteries, etc were working well for my gig tonite and I heard that raspy sound out of the top speaker again, and at very low volume. I tried other basses, amps, cables, checked batteries, etc and it still sounded bad. The more I turned up the volume and with each note I plucked, it was like hearing the glue gradually seperating, to my ears. So Jim is sending out another driver but he said I may get billed if Eminence finds I damaged the driver. I guess if its the same cause as the the last one, I will take the hit this time. I had thought of just buying a new Deltalite 2015 or Kappa 3015 to drop in the cab instead. But dont know if that would fit with the NV cabs tuning. Guess I'll drop the new driver in and wait to see what they find.
But I must reiterate, I've never played thru a cab so softly as I have thru this cab. I use 2 GB Neox 212T's in my other band where I get no PA support. I usually use my GK1001RBI with the NV cab, 540 watts @ 4 ohms. And I have used my B1500 with it, stand alone, but it was set all flat, cept mids boosted a touch. And used my Peavey Cirrus 5 flat and the bass knob backed off, this bass has a very mid-heavey tone. So I can't see where I am causing the damage but I understand it could be possible. I've always used ported cabs and maybe this sealed cab is not for me, can't really say.
I've been vasilating over selling/trading the NV for a ported 410, guess its time to consider this again, but I'll play it again wth the new driver at one more gig to be sure.
Hi.
The only unwound coils that I've seen have been in ancient speakers, the newer samples have just had an open somewhere, perhaps some scorching, but usually the epoxy has held the coil together. Perhaps Eminence had some kind of a problem there?
+1 to the correct cab, before You damage another driver in the same manner.
So what cab? Or alternatively what internal volume and tuning/ports?
And most importantly, what driver?
Regards
Sam
Edit: And the answer appeared before I could type the question
The only unwound coils that I've seen have been in ancient speakers, the newer samples have just had an open somewhere, perhaps some scorching, but usually the epoxy has held the coil together. Perhaps Eminence had some kind of a problem there?
+1 to the correct cab, before You damage another driver in the same manner.
So what cab? Or alternatively what internal volume and tuning/ports?
And most importantly, what driver?
Regards
Sam
Edit: And the answer appeared before I could type the question
Since You're not a newbie I'm sure that You checked the polarities of the speakers, and since the cab is sealed, the over-excursion caused by going lower than the tuning frequency is most probably out of the question too.
The problem sounds very strange, a 215 should be able to handle a 5er. An air leak somewhere could be the answer, but to be able to do damage that easily, it should be audible.
Regards
Sam
The problem sounds very strange, a 215 should be able to handle a 5er. An air leak somewhere could be the answer, but to be able to do damage that easily, it should be audible.
Regards
Sam
the driver I pulled from the cab is a Eminence BAS15-2508, 8 ohm. Did not see that on the Em website. Are they special ordered by Berg for this NV cab? And when I last played this cab at a gig, about 2 mos ago, it sounded fine the enitre nite and I only listened to it again last nite when I heard the raspy noise. When I pulled the driver, I gave it the lite hand push method and can just barely hear the rubbing sound. It actaully sounded pretty OK in the cab as I ran some scales but as I plucked a little harder the distortion was quite prominent, esp on the B string notes. All I can do is wait to see what they find out about the burnt driver down the road, I think its gonna cost me this time. Jim says like 1 in 2000 of these drivers come out bad, those are long odds to get 2 of em, ya think, 
They might have had an "issue" at the voice coil manufacturing stage..... I think Eminence gets a bunch of stuff done in china now, so it may be typical low-ball vendor QC issues. They USED to make it all in their own factory, which I have toured.
In any case, if the glue system is damaged by heat, or if it just wasn't done right, part of the coil can begin to slide on the former. No distortion of the former is required.
If you keep playing, you get progressively worse distortion and buzzy harmonics, until finally a wire is flexed so much that it breaks.
A true "unwind" where the wire actually "shells off" the former is a related issue, where the glue is broken down enough that individual wires come loose.
BOTH are usually due to GROSS overpowering. Can also be due to a DC offset in the amp shoving the speaker off "center" and causing one part of the voice coil to have poor cooling.
Or it can be because of a manufacturing problem that causes the voice coil to be improperly centered to begin with.*
From what you say, it seems unlikely that you overpowered it that much, so it seems likely that there is a QC problem. Either at assembly or at coil manufacturing. (maybe Eminence needs to bring their coil winding back in-house again.... assuming they sent it away to china as I had heard they did.)
* If the coil is for any reason not centered, then some of it may stick out past the "front plate" of the magnet. That means it does not get properly cooled, and that part can overheat drastically, with damage to the glue and wires falling off as a very possible result.
Most voice coil cooling happens from heat radiating to the colder magnet structure from the hot (200 to 300 degree) voice coil. If that cooling cannot happen, the coil will be fried.
In any case, if the glue system is damaged by heat, or if it just wasn't done right, part of the coil can begin to slide on the former. No distortion of the former is required.
If you keep playing, you get progressively worse distortion and buzzy harmonics, until finally a wire is flexed so much that it breaks.
A true "unwind" where the wire actually "shells off" the former is a related issue, where the glue is broken down enough that individual wires come loose.
BOTH are usually due to GROSS overpowering. Can also be due to a DC offset in the amp shoving the speaker off "center" and causing one part of the voice coil to have poor cooling.
Or it can be because of a manufacturing problem that causes the voice coil to be improperly centered to begin with.*
From what you say, it seems unlikely that you overpowered it that much, so it seems likely that there is a QC problem. Either at assembly or at coil manufacturing. (maybe Eminence needs to bring their coil winding back in-house again.... assuming they sent it away to china as I had heard they did.)
* If the coil is for any reason not centered, then some of it may stick out past the "front plate" of the magnet. That means it does not get properly cooled, and that part can overheat drastically, with damage to the glue and wires falling off as a very possible result.
Most voice coil cooling happens from heat radiating to the colder magnet structure from the hot (200 to 300 degree) voice coil. If that cooling cannot happen, the coil will be fried.
Note to Eminence. All of us bass player would gladly pay a few extra dollars to not have these problems. Yes they actually do read this forum. Gassp.
I like your argument, allow me to quote you if I need to fight my case later. I don't imagine I can argue that I've gotten 2 bad drivers, even if that holds true. Seems the symptoms they describe are gonna be due to user abuse. But I still don't feel I ever pushed this cab hard at all.
I just did a gig tonite with a Eden D210T cab w/ TBer installed Em Deltalite II 2010's and a GB Neox 212T w/B1500, since I could not use my NV215 as I planned. It sounded quite awesome and I get no PA in this band. But I understand electronics can do ugly things now and then, so I wont be surprised if they say I did damage to the NV215 cab, but man, I felt I was being so careful with this cab. Jim says he will send a new driver to music store I bought cab at and that he wants the damaged one back, good maybe they can figure out whats what. Tho I feel their gonna wanna bill me for this one, this time. Should I have just sprung for a new EM 15", 2015 or 3015, on my own, I'm sorta scared to try this cab at a gig now. I'll prolly just drop the new driver in and post this cab for sale/trade on local CL listing. We'll see.
I just did a gig tonite with a Eden D210T cab w/ TBer installed Em Deltalite II 2010's and a GB Neox 212T w/B1500, since I could not use my NV215 as I planned. It sounded quite awesome and I get no PA in this band. But I understand electronics can do ugly things now and then, so I wont be surprised if they say I did damage to the NV215 cab, but man, I felt I was being so careful with this cab. Jim says he will send a new driver to music store I bought cab at and that he wants the damaged one back, good maybe they can figure out whats what. Tho I feel their gonna wanna bill me for this one, this time. Should I have just sprung for a new EM 15", 2015 or 3015, on my own, I'm sorta scared to try this cab at a gig now. I'll prolly just drop the new driver in and post this cab for sale/trade on local CL listing. We'll see.
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
Isn't the NV215 sealed? That removes the 3015 from consideration. If it's sealed it has less sensitivity in the low end than a vented cab, and less sensitivity is an invitation to overpowering, which may lead to a cooked coil.
Yeah was just thinking out loud about other drivers but I have the original driver coming next week, thanks yet again Jim. Now Im nervous about all my cabs. At last nites gig I used two, 4 ohm cabs with B1500 but I used my series box so as not to run all this big amps power into these cabs. Now, that would make this a 8 ohm load, correct. Still supposed to be about 800 watts @ 8 ohms from this head, sounded very nice still.
I could not tell the difference in volume just bummed I can't use my speakon cables. Maybe I'll try my NV215 w/210, again both 4 ohmers, using the series box inline and see if I can make this new driver last this time.
Sign me: nervous to rock now
I could not tell the difference in volume just bummed I can't use my speakon cables. Maybe I'll try my NV215 w/210, again both 4 ohmers, using the series box inline and see if I can make this new driver last this time.
Sign me: nervous to rock now
Are the motor assemblys accesable for rebasketing on the neo speakers ? Maybe some ferro fluid would help with the problem if it isn;t already factory installed.
Is this directed at my NV cab issue? Most certain this cab does not use neo drivers but maybe I'm misunderstanding your query. Or are you speaking in general?
Speaking more genrally. Ferro fluid is a great upgrade if the motor can be taken off the basket. I did my peavey black widows 15 yrs ago and punished them with no fialures to report.
Do you have a source for Ferro Fluid? I haven't been able to locate any lately, I've replaced some horn dia. and need to replenish a couple of drivers.
parts express used to carry it online. I can't find it the catalogs try calling customer service.
Ferro fluid definitely changes the speaker response....... it changes the suspension friction, by adding the fluid viscosity effects.... Can be noticeable, drastic, or minor, depending.
I typically put a little bit in at a time. Usually it seems to make marginal speakers like Peaveys old scorpions much less brittle and harsh and alot smoother. Same for the Old Black widows.
