generally caused by a amp being pushed into distorted clipping and this generates heat in the speakers voice coil ruining it eventually. just a laymans definition. they can also catch fire....
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When the vioce coil inside the speaker gets forced beyond it's design parameters.
The coil can be bent, can be partially shorted out...Or melted.
(that inner coil is usually a coil of wire wrapped around a tube form, closely fitted in the magnetic gap. It has to be perfectly round, as the gap is usually very small, some coils are thin, some deep, some very large around.. depending on the design. that coil is attached to the back of the cone or dome of the driver. It rests inside the magnetic field created by the big magnet around the back of the driver.)
The damage can cause a rasping sound, or a lessening of response compared to the other coils. The bent coil can stick in the gap, or the melted insulation can stick in the gap.
The other sort of blown, is the surround is separated from the body of the cone.
Usually that happens with age, but a really serious overdriven speaker can have that happen. along with the inner voice coil being damaged.
Is there a way to test the speaker to see if there is a problem. The reason I ask is that in one of my speakers, when playing very loud, I heard a sudden rasping sound.When I reduced the volume, it sounded ok. It can still play quite loud without the rasping sound, but I dont really want to play it again as loud as it was to see if the sound comes back. IT was really loud, Pink Floyd Dark Side of Moon, Money. Quality amp of 275 watts, playing vinyl.
If you can move the driver over to the other speaker; pay attention to which wire goes to the proper terminal of the driver to see if the problem moves;if it moves then you have identified the driver as being bad.
If these are a expensive or special driver and is damaged I would talk with Bill Legall of Millersound to get his opinion;he is highly respected in the business and his work is of the highest caliber.
1422 Taylor Road
Lansdale, PA 19446-1531
I would play It but not SOOOOO loud. You might have been clipping the amp. How loud is loud? I play hard rock over 90dbs at times like RUSH with lots of bass with out glipping my amp at all. But I have a Krell FPB 400cx. If you love It LOUD you better have lots of good clean power. Clipping a amp will blow any speaker no matter how good It is. You can never have to much power as long as It's good clean power. LOL
Tough question, alot of partial answers here. There are different ways a speaker can be blown. It is possible for a speaker to run out of excursion limits (travel), when this happens, you normally would hear a popping sound before it is too severly damaged. That popping is the voice coil former bottoming out against the magnet, then the voice coil is damaged from slapping against the magnet or the cone rips from too much travel as you stated in your question. The most typical problem has been somewhat addressed above by others. Amplifiers are driven to clipping, the voice coils heat up and either come apart or get so hot that they may partially melt and seize the cone. If a cone seizes its obvious, it is frozen (won't move). If the coil has partially come off the former, that is where you will hear a rubbing or garbled sound. As Elizabeth stated, you can put your fingers on both sides of the center of the cone and push evenly, if the coil has shifted, you will hear or feel a rub. If the tweeter is blown, most designs have replaceable diaphrams, its kinda like a recone on a mid or woofer. Reputable woofers and mids have recone kits available. It is very important to get the correct kit, the weight of the cone and stiffness of the surround and other things must all match for the performance to be the same of the original driver. Lastly, it is possible for a component to be bad in the crossover, typically a burnt resistor or a electrolytic cap can burst. So when you say, "what actually happens" it is a very broad question. I have given you a very broad answer, but one that I hope makes sense. Good Luck, Tim
the crossover is not viewable or easily accessible. I will be taking it in to a dealer today to see if they have the tools to open it up. I cant imagine it would be a fuse that would not be accessible to the user. there is no sound at all from any of the three woofers in that speaker, but the midrange and treble work fine.
ok, got the verdict today. the crossover was broken in two and laying at the bottom of the speaker. Unlikely caused by overdriving. I also doubt it happened in shipping as the speakers were well packed in the factory boxes. I suspect the original owner dropped the speaker at some time, causing an impact enough to crack the crossover board and perhaps later vibrations finished the job. Anyway, it will be replaced and fixed.
This was an interesting voyage of investigating a problem that wasnt apparent on first examination. Easy to jump to conclusions on partial information.
Don't rule out the shipper dropping the package as this happens a lot more than one would think. The package could drop and land flat, so no damage would be evident to the box or the outside of the speaker, but cause internal damage like you're speaking of mainly because of the weight of the contents.
I would think there would be visual damage outside the speaker, or at least markings if someone dropped a speaker that wasn't packaged?