I think my sub comitted suicide..
 

First this is what I'm running:
SUB:10in Kicker CVR (dual 4ohms)
-In parallel (2ohms)
-sealed enclosure
AMP:Alpine MRP-M500
-Single channel, 500WRMS @ 2ohms
Wire:4 Gauge Pos&neg

AMP2:4channel 400wRMS (100w per chan) (I build this one. In my electronics engineering program)

history:
I've had this sub since July/august and Haven't had any problems with it. I use it all the time for driving around town, But every month or so I ran it for 3 hours+ straight. (This is because about every month I drive to see my parents) I never ran it at the full volume, just cause it doesn't suit my music taste (metal, which is why its a 10in for faster response)
What I'm trying to say is I ran this sub through its paces. But never ran it above spec.

What happened:
So today I was driving back home from my parents place and then my sub just cut out. First I thought the amp just over heated as with my Clarion APX-1301 (400Wrms class A/B) it happened all the time. So I thought just with that amp, this one had a built in thermal cutoff. So I pull over and It seems fine. A little warm, but after turning it off and then back on, it works. How ever as soon as I start to turn the volume up (to a fair level) it cuts back out again.
When I was running it today (when it broke) I didn't even have it that loud. I usually listen to it much louder.
When I get home, I starting troubleshooting the sub/amp.
With my multimeter and the deck at low volume (so the sub is actually on) I notice that I'm getting an output out of the amp. But as soon I turn the volume up, it cuts out again and the output reads 0.
With out the sub connected, the amp happily outputs at all levels of volume.
Keeping in mind, my sub is a DVC@ 4ohms each (in parallel[2ohms]) I decide to test the impedance. It reads out 1ohm. I sigh and pull the sub enclosure out.

The Fun
At this point I'm starting to think its the sub. So I pull the sub/box out of the car and get ready to examine the sub. Soon as I pull the sub out of the box, the 'Magic blue smoke' fills the room. (For those that may not know, The 'magic blue smoke' is what comes out of electronic devices when you overheat/short/blow up the device. The magic blue smoke never goes back into the device. Thus broken)

What backs up my theory of the sub committing suicide is when I test the voice coils for 4ohms, I don't get 4 ohms. With the first voice coil I get ~1ohm, and the second I get the same. But when I read across two of the voice coils (which AFAIK shouldn't be connected, thus infinite ohms) I get ~1.5ohms.
Basically I get ~1.5 ohms no matter where I put the probe on the Multi to the terminals on the sub.
From what I can see, the sub has no noticeable damage to it.

Conclusion
I believe my subs voice coils have melted/fused together. What surprises me is that my amp survived this. Usually electronic devices (like amps) don't like it when the output is shorted to ground (or in this case, negative terminal)

What do you guys think? Why did this happen? I thought kicker had quality with their subs/amps.
What I really don't understand is why it ran for ~6months then running it less then what I normally do, it just crap out like that. Hopefully someone can shed some light on the matter.
I believe the sub is still under warranty, so if you guys think its the sub I'll return it.

Thanks for the help, and sorry for it being so long. I thought afterwords that titles might make reading it easier.


Explanation of the multimeter
I know the best way to see the amps output would be to use an oscilloscope. But with the multimeter on AC you can see the RMS voltage coming out. While not too useful on its own (as it doesn't read it that fast), I could still compare the Vrms with the volume at high and low. So I could tell that without my sub connected, I was actually getting a higher output (at higher volumes VS reading 0.)

It is not the sub..... it was you..... a sub only does what it is told to do. You feed it a clipped signal, it plays a clipped signal. You feed it a clean signal, it plays a clean signal. What the real problem was is simple and you said it yourself.

"But every month or so I ran it for 3 hours+ straight"

A sub must be allowed to cool down. Heat in all cases is what destroys a sub (aside from a mechanical issue). You did not allow the sub to cool down. A sustained level of output, not just full output, creates a enormous amount of heat. If the heat cannot be dissipated, the magic smoke is going to be released. It does not happen instantly in daily driver cases, it happens in a slow downward spiral, each time it is heated up, it looses it's ability to cool. Eventually that downward spiral hits bottom and the magic smoke genie rears his head.

Wow, really? I'm aware that heat is bad for all electronics, and without it being dissipated it can damage. I thought these things where designed to run in high temperatures. Considering that its spec'd for both ported, and sealed enclosure.

So I guess I really did melt the voice coils? I wish the sub looked more melted/mangled. At least I would have cool pictures.

Is there anything I can do for the next sub? Would a ported box be better. (only problem with that is if its not tuned right, I just wasted ~$50-80. [ebay with shipping])
Can I do anything to a sealed enclosure to help cool the amp? (as a fan would only circulate the hot air around it self)
How is kicker for quality? Could a Alpine Type R take more of a beating (temp wise)? Should I get another kicker, and take it easy?

Your answer makes sense, now that I know subs can't take THAT much heat and how it works ("in a slow downward spiral").
Anyone else agree?

thanks for the reply, and helpful info.

I would be more worried about the damage to my ears than my subs after 3+ hours of full volume listening. Really dude do you need to have it that loud for that long? You can permanently damage your hearing with just an hour at 120dbs. Turn it down man and you will enjoy your hearing for a little while longer. Any ringing in your ears after doing this for 3 hours? Trust me the damage to my ears is so bad it is hard to get to sleep at night due to the loud ringing in them. It is just not worth the damage to your ears and equipment to do this for 3+ hours at a time.

Although the overheating/melted voice coil make sense, the reason I doubt it is because I don't listen to it at max at all. (I can guarantee you its not at 120dB. I'm not running competition stuff.) I have it just loud enough that I cant hear the traffic, just the music (this includes sub and the other amp for the speaker. Like I said above I have the sub loud enough to complement my mid/highs. Not mind blowing, window shattering loud bass). But without knowing how hot the sub actually got, I have no way of knowing for sure. Other then, so far, it being the most plausible (over heating).

I'm aware of the 'ringing' in the ears when listening to really loud music means your damaging your ears. I'll admit that it is present, but no where near as bad as when I go to a local metal show.

A quick update:
When I move the cone on the sub (push on it) it makes a terrible grinding noise.
So I guess that's a definitive answer on what the problem is.
haha... damn it.

voice coils dont really melt. they can heat up real bad, begin to scratch against the pole and eventually unwind. to actually melt it you'd need something like a 1000 degrees celcius.

You should consider a career in writing. That first post was very well done.

Although Mr Tuner is quite knowledgeable, is a vendor, and works the board hard (as is his right as a paying vendor), there is also the possibility the sub had a manufacturing defect.

If you think of the tens of millions of subs out there, with the VAST majority most likely not installed ideally, then it follows there would be
a massive return rate on them. Who knows though, maybe you just drew the short straw this time.

Cheers mate.

John

John, funny you should mention that about the manufacturing defect. I was going to mention that in my post but after reading through his symptoms, decided that it was the wrong diagnosis for the sickness. A manufacturing defect is indeed a possibility with a sub failure, in his case though, it is highly improbable.

well i read his post too and i must say nowhere does he state he listens to his music loud. "fair level" while still being able to hear traffic to me sounds like it is not loud at all!

people here pound the hell out of their subs all day long without a problem.

the fact that his are less than 5 months old with what sounds like below spec (as long as its clean) power can only mean one thing!
do you have the receipt for these? if so contact the manufacturer and start a warranty dialog with them. worst case is they say its not covered. at most you get new subs shipped to your door free of charge to you.

to me it sounds like he got the "short straw" as John_Taylor said. i am no expert here buy any means. like i said above, at most you get replacement subs.
it cost you nothing to try and everything not to.

gl