Coil rub cause amp to blow?

[It happens 10+ year member]

I was curious if having coil rub or a off balanced/ non linear coil cause a amp to blow out? Thanks in advance

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[Doxquzme Premium Member]

That happens. I had a $1000 dollar FOCAL where the magnet shifted and froze the coil. I returned it as you can’t know what the condition of the coils is after such a thing. If the coil is no longer rubbing you may be lucky if it is no longer an issue. That said, if enough rubbing occurred to damage the windings, that may have created a condition where it shorts out intermittently, this could cause the amplifier to fail if no voltage or short protection is present. Have you had the woofer tested, do you have a way to test the continuity of the woofer coil with your own equipment (A millimeter)? Try testing the woofer with a common household flashlight battery (or any C,D, AA,AAA). Hook up the driver voice coil leads to the battery maintaining polarity S(+) to B(+) and S(-) to B(-). The cone will move up and stay there if they are held in place. If they move up and then back down on either coil or don’t move at all, you most likely have a coil that has a short in it. Is this the first amp you hooked up the driver too?

 

[Doxquzme Premium Member]

That's user error you're describing...you can run a 100w amp to drive a 1k rms sub without damaging anything...just set your gain properly and you're golden...granted the sub will not get loud but you won't hurt the driver under powering it...

Your statement is conditional, not actual. You can destroy any speaker with gains set to cause clipping above an acceptable level – it will ruin any driver attached to it. As long as you don't drive the amplifier into clipping, it won't hurt, but it's not very easy to hear a small (but big enough to kill a driver) distortion on a subwoofer, so many people kill their subs by under powering them and pushing the amp too far without knowing it. The same in essence as incorrect gain settings causing the issue which would be a condition imposed by the user, not applicable laws of physics.

 

[spokey9]

Your statement is conditional, not actual. You can destroy any speaker with gains set to cause clipping above an acceptable level – it will ruin any driver attached to it. As long as you don't drive the amplifier into clipping, it won't hurt, but it's not very easy to hear a small (but big enough to kill a driver) distortion on a subwoofer, so many people kill their subs by under powering them and pushing the amp too far without knowing it. The same in essence as incorrect gain settings causing the issue which would be a condition imposed by the user, not applicable laws of physics.

That's failure due to improperly setting your gain...that's not failure from under-powering a sub...there is a difference...

If you want to say you can smoke a sub because you cranked the gain up to 11...I'll agree with that...but that's not damage from under-powering...

 

[Doxquzme Premium Member]

That's failure due to improperly setting your gain...that's not failure from under-powering a sub...there is a difference...

And that’s quibbling.

If the result of improperly setting the gains is that you clip the amp, the result is the same. Blame under powering or user error, it’s to be avoided either way. The purpose of a gain control is to tune the amp's input stage to accept the head unit's voltage level, and for the vast majority of people, not to manipulate it so that you ca squeeze extra power by clipping the amp. It’s simple really, when you blow a speaker from too much power, you pushed the speaker beyond it’s capability. When you blow a speaker from clipping, it’s due to overdriving the amplifier. Fried equipment either way, regardless who the user is that didn’t know what they were doing.

I’m still trying to figure out why the OP is still trying to use a driver that had rubbing that apparently he has now corrected. I’d be willing to bet that one of or the single VC has an intermittent short in it and that can cause the amp it is hooked up to fail if the amp does not have built in voltage/short protection

 

[Jimi77 5,000+ posts]

Didn't say it creates it.

The relationship between clipping level and DC voltage is, In summary, the clipping level is directly related to the DC voltage in a circuit, as it determines the maximum amplitude a signal can have before it gets distorted. Clipping circuits cut-out (chop) part of the input. Clipping circuits always add a DC voltage to the output. AND, yes, clipping circuits may be used to add a DC bias to the input. Clipping circuits can turn sinusoidal waves into square or triangular waves. All this is correct but in the end. The answer to the OP is:

Your woofer is broken or damaged and you should not use it on any amplifier or it will most likely result in something getting fried.

I'm not sure where you learned electronics, but whether it was multi-million dollar military radar systems or replacing OP amps in HUs, I never heard of or seen a functioning AC circuit producing DC because of a messed up gain structure. If the output x-sistor shorts to rail voltage, then we would have DC voltage, which isn't going to last long before something else catastrophically fails. If you use a DC input signal then I can force the AC circuit to produce DC. Otherwise AC circuits are AC circuits, in this case it's just distorting the signal.

For example, in the a case of a clipped signal, we wouldn't calculate the increase in voltage, power and current using DC voltage. We would use AC voltage to do our power calculations (AC voltage =the area under the curve - see image). The extreme example would be a unclipped square wave, which would double output without clipping yet would certainly be AC voltage. Many DC to AC convertors use square waves or a variation of them.

https://i.mtx.com/mtxcom/clipped-signal.jpg

 

[Jimi77 5,000+ posts]

That's failure due to improperly setting your gain...that's not failure from under-powering a sub...there is a difference...

If you want to say you can smoke a sub because you cranked the gain up to 11...I'll agree with that...but that's not damage from under-powering...

As a matter of fact, you didn't underpower the at all, you cranked the gain to 11 which overpowered the sub, exceeding it's thermal rating and you get that lovely burning smell.

 

[Jimi77 5,000+ posts]

I’m still trying to figure out why the OP is still trying to use a driver that had rubbing that apparently he has now corrected. I’d be willing to bet that one of or the single VC has an intermittent short in it and that can cause the amp it is hooked up to fail if the amp does not have built in voltage/short protection

Because he wants an excuse to buy a new amp???

 

[Doxquzme Premium Member]

As a matter of fact, you didn't underpower the at all, you cranked the gain to 11 which overpowered the sub, exceeding it's thermal rating and you get that lovely burning smell.

Because he wants an excuse to buy a new amp???

That's as good a reason as any! I'd never risk using a coil that "had" rubbing issues, not worth it unless you can prove beyond a reasonable doubt that it's not an issue. Doesnt take much to rub a goil the wrong way!

 

[Doxquzme Premium Member]

I'm not sure where you learned electronics, but whether it was multi-million dollar military radar systems or replacing OP amps in HUs, I never heard of or seen a functioning AC circuit producing DC because of a messed up gain structure. If the output x-sistor shorts to rail voltage, then we would have DC voltage, which isn't going to last long before something else catastrophically fails. If you use a DC input signal then I can force the AC circuit to produce DC. Otherwise AC circuits are AC circuits, in this case it's just distorting the signal.

For example, in the a case of a clipped signal, we wouldn't calculate the increase in voltage, power and current using DC voltage. We would use AC voltage to do our power calculations (AC voltage =the area under the curve - see image). The extreme example would be a unclipped square wave, which would double output without clipping yet would certainly be AC voltage. Many DC to AC convertors use square waves or a variation of them.

https://i.mtx.com/mtxcom/clipped-signal.jpg

I'm not sure where you learned electronics, but whether it was multi-million dollar military radar systems or replacing OP amps in HUs, I never heard of or seen a functioning AC circuit producing DC because of a messed up gain structure. If the output x-sistor shorts to rail voltage, then we would have DC voltage, which isn't going to last long before something else catastrophically fails. If you use a DC input signal then I can force the AC circuit to produce DC. Otherwise AC circuits are AC circuits, in this case it's just distorting the signal.

For example, in the a case of a clipped signal, we wouldn't calculate the increase in voltage, power and current using DC voltage. We would use AC voltage to do our power calculations (AC voltage =the area under the curve - see image). The extreme example would be a unclipped square wave, which would double output without clipping yet would certainly be AC voltage. Many DC to AC convertors use square waves or a variation of them.

https://i.mtx.com/mtxcom/clipped-signal.jpg

“If the output x-sistor shorts to rail voltage, then we would have DC voltage, which isn't going to last long before something else catastrophically fails. If you use a DC input signal then I can force the AC circuit to produce DC. Otherwise AC circuits are AC circuits, in this case it's just distorting the signal.”

Agreed, not going back an re-read to clarify or correct, not sure where I misspoke. Anyhow, at the end of the day, over the heads of most non EE’s in here. Good engagement and good to know that there are enough that have good working knowledge, practical and applicable by experience or learned.

 

[hispls 5,000+ posts]

The shape provides the conduit for DC to enter into the circuit.

If your amplifier is outputting DC voltage the cone will either pop out or in and not move whatsoever. Apart from catastrophic failures of a small handful of circuit designs I can't say I've ever even heard of this happening. Where did you come up with this theory?

 

[Doxquzme Premium Member]

If your amplifier is outputting DC voltage the cone will either pop out or in and not move whatsoever. Apart from catastrophic failures of a small handful of circuit designs I can't say I've ever even heard of this happening. Where did you come up with this theory?

I was referring to distorted current, when the signal is clipped. Got DC stuck in my head, just a brain fart. One should not drink and forum!

 

[hispls 5,000+ posts]

distorted current,

What is that even supposed to mean? I can guarantee this is NOT a term you would find in any electronics textbook.

 

[Doxquzme Premium Member]

Not a term, a description. When it clips, it sends a distorted signal (current) through. A square wave contains more energy than a sine wave and when sent to a speaker this energy will either go to the same driver as the sine wave did before it clipped, or to different driver(s) covering higher pass bands (not applicable in this discussion) If an amp is too small and is driven too hard it clips". Well, don't clip the amp. A small amp clips earlier than a big amp, sure - but don't clip the amp, never clip the amp in normal listening environments, no reason to in my opinion.

Small amplifiers can fry a speaker, trying to play a signal of amplitude X, but clipping it (whereas a larger amp would play amplitude X unclipped), is because the clipping might direct part of the energy to higher pass bands and fry them. It won't fry the same lowest pass band driver that would survive a larger amp playing the same signal unclipped, because in total the amount of energy is smaller with the little clipping amp - not larger, and not even as large. A, there is that as one poster indicated. Does not mean that a small amp can't, but usually won’t, even to clipping. It will still fry drivers of higher pass bands, yes, but not because of Direct Current, sorry, misspoke. That said, I don’t think its good advice to give the average Joe that controlled clipping is a good thing, for most it's not because they for one don’t know the potential for damage to their equipment and two don’t know how or what tools to use to measure it accurately enough to take advantage of it (and only in a subwoofer setting). My experience with damaged subs has shown more of them are blown when the sub is underpowered, not the other way around for obvious reasons. At the end of the day, got a little of topic but think that we all covered the OP's issue. If you had a sub where the coil(s) is, are rubbing (basket or magnet alignment issues), then repaired and you use it anyway, you run the risk of damaging the amp, as it appears to what has happened here. Unless you have verified that there was no damage to the VC, not worth the risk.