How to blow a speaker?

[autocross]

Maybe I am being paranoid, but last night a guest sat on my remote and the volume shot all the way to the max. I am using an Onkyo 602 on F-3's and was able to quickly get the volume down, but it sounded very distorted. I am thankful I was listening to Coldplay and not Metallica.

My question is, what makes a speaker blow? I searched and searched, but could not find a good answer. After listening for several hours I think they are fine, but I am curious if anyone thinks I may have permanently damaged them.

I read on a post I found that the reason most speakers are damaged is that they are overdriven for a period and the voice coil overheats. How long is this period? Do short bursts of overdriving cause the voice coil to overheat or does it take a sustained period of stupidity?

Are there other causes of speaker failure? Any true experts out there please respond.

[ygmn]

normally it is when the amp sends a clipped wave form in lieu of the correct waveform...

this clip causes damage to the voice coil...

[Spkrdctr]

I have done a lot of destructive testing on speakers and your F3s are fine. You would know right away if you had any real problems. Klipsch speakers are pretty tough. It is now time to enjoy them!

[PrestonTom]

I have done a lot of destructive testing on speakers and your F3s are fine. You would know right away if you had any real problems. Klipsch speakers are pretty tough. It is now time to enjoy them!

Consider yourself lucky.... it could have been worse. I agree that your speakers are probably fine. Let me mention two things however.

First, the issue of clipping means that the waveform is "squared off at the top". This can mean that DC current is being sent to the driver. That is bad & and it can damage the driver (specifically the voice coil). Diaphragms can also be damaged if they over driven.

Second, there is no reason ( & I do not want to hear about some audio voodoo) not to incorporate fuses into you speaker connections. Go to Radio Shack and get their 20 mm in-line fuse holders and attach these to the + side of the speaker wires to each cabinet. This is good insurance (and it does NOT degrade the signal quality).

Good Luck,

-Tom

[WMcD]

I think that if they are sounding okay, there is no damage to worry about.

BTW I blew a T-35 tweeter by inadvertently applying a very loud test tone. The T-35 lasted about 5 seconds. I couldn't get to the amp in time to turn things down. In a way, like your situation.

Tweeters are most prone to failure because the voice coil is wound with very thin wire. About the size of a human hair. The T-35 tweeter is rated for about 5 watts of continuous power. That is probably less than a flashlight bulb. Midrange and woofers are wound with thicker wire. It is still relatively thin.

This is why we here see so many reports of tweeter failure. It is sometimes in an existing system after a party, or something purchased second hand.

This is also why the first test to make is with an ohm meter. The meter shows up an open voice coil immediately. D.C. resistance should be about 8 ohms, but a blown coil is infinite resistance, i.e., "an open circuit."

The reason they do survive when hooked up to a high power amp is that the crossover filter makes sure that they only get the highest frequencies, and music doesn't have sustained frequencies at high levels. Sharper filter roll offs are better.

It is interesting to read the review of the Forte. the reviewer put more than a kilowatt into it. But this was in short bursts. I infer from this that most failures are not caused by mechanical forces alone.

There are some exceptions. If you hit a woofer with high level tones, particularly at its resonance, you can hear the voice coil former or some other part hitting the magnet. It makes an odd clanking sound. Left to go too long, it is going to cause a mechanical failure of the woofer.

I think in most cases, the copper wire in the voice coil get too hot. Like a fuse, it just melts at some random spot. .

There is a point of common wisdom that when an amp goes into clipping in the bass, the signal is rich in harmonics up to tweeter frequencies. There is math and measurements to show this, however a close look at both shows the high frequency components are not very strong. It is the Fourier analysis.

In my view, if you drive an amp to clipping with music (which has a wide specturm of frequencies), there is just a lot of power in the high frequencies, and all frequecies. So it a train wreck in the making. No fancy math is necessary. It is difficult to say what fails first.

Going back to failure modes. I think that is your question.

The voice coils are made of enamaled wire which is wound on a "former" which is a tube made of cardboard or some other material. The windings are held on with some sort of glue. Much effort is made to use materials which don't soften from heat. None the less, they do soften if heated enough. There are even reports of fires..

So you can get to a situation where the wire heats up but not enough to melt the copper wire. Rather the former and glue fail or get mushy and distort.

You might know that the voice coil sits within a circular gap of metal which focuses the magnetic field. There is very little clearance. So if the voice coil and former warp from heat, it can cause mechanical binding. You get some sound but at a reduced level. This is why people test for binding by trying to move the woofer diaphargm by hand. There is a distinct binding. We can't get the diaphragm of a horn driver to try that without taking things apart.

Going to midrange horn drivers. Some (all?) of the non-Heritage drivers are made with plastic housing. One of the moderators here, long ago, reported an incident where the housing had melted. It just shows that over driving long term is a bad thing. New failure modes are created.

So you can see the line up of failure modes, and lets recap::

1) Very short term high power is okay as long as the copper and former glue can cool.

2) Somewhat longer, but intense signasl, will melt the copper winding before it can disapate the heat into the former and glue.

3) In the next step down, the copper doesn't does not melt but it transfers enough heat into the former and glue to warp them.

4) If you hit a driver with a lot of power at resonance where it is moving a lot, you can cause mechanical damage without heating.

5) Of couse you can see that combinations of the above can gang up on the system. High mechanical forces when heat has weakened them.

Best,

Gil

[hillbilly]

I think they're fine. After being a stereo nut for a long time, I have concluded that distrotion kills speakers more than power. People would brag how their amp was so bad *** that it blew their speakers. Yeah, after listening to them too loud for many hours. Like Gil was saying, you can push on a woofer with your hand (apply force evenly) and if you hear a scraping sound then it's got a warped voice coil. That's what I saw with people's car stereo subs. Tweeters, once they blow, just quit playing. (in my experiences) I don't know alot about horns, I am on my first set right now. I have seen a huge amplifier cause a woofer cone to actually physically seperate it's self from the surround, but that was not what you have. It was a big new amp and a crappy 8" speaker. We did it (in high school) just to see if we could. I've also seen melted crossovers. That shouldn't be a problem for you either though, since you turned it down quickly. Good luck.

Ian

[tkot]

i agree with what was mentioned above

if they still play and sound ok they are most likely not damaged.

i have had several voice coil fires

(the ones that fill the room full of smoke)

remember if you let the smoke out, their done!!

jay

[Remotia]

2-main ways:

too much heat on the vc, which would have been unlikely in your case because you only had it loud for a very short time.

or, mechanical damage. The vc slams into he back of the magnet and something gets bend or forces the cone too far forward and tears the suspension or worse, the vc rips right through the cone... thats always funny too.

[Remotia]

think they're fine. After being a stereo nut for a long time, I have concluded that distrotion kills speakers more than power. People would brag how their amp was so bad *** that it blew their speakers. Yeah, after listening to them too loud for many hours. Like Gil was saying, you can push on a woofer with your hand (apply force evenly) and if you hear a scraping sound then it's got a warped voice coil. That's what I saw with people's car stereo subs. Tweeters, once they blow, just quit playing. (in my experiences) I don't know alot about horns, I am on my first set right now. I have seen a huge amplifier cause a woofer cone to actually physically seperate it's self from the surround, but that was not what you have. It was a big new amp and a crappy 8" speaker. We did it (in high school) just to see if we could. I've also seen melted crossovers. That shouldn't be a problem for you either though, since you turned it down quickly. Good luck.

Ian

Yep, this happened to one of my subwoofers, my VC overheated and it scraps on the side of the magnet. This was in conjunctin with the amp blowing too! Talk about overdriving a sub! Lucky for me it was all under warranty (BTW it was NOT a klipsch sub )