Mechanism of damage

Shizelbs

School me.

I've read it plenty, but never with a proper explanation.

What is the mechanism of damage, in other words, what exactly happens when damage is caused by underpowering speakers?

shack

Shizelbs wrote:

School me.

I've read it plenty, but never with a proper explanation.

What is the mechanism of damage, in other words, what exactly happens when damage is caused by underpowering speakers?

You know what clipping is but here is the best explanation I've seen of what it causes in the speaker.

The amp tries to put out the appropriate power, but runs out of voltage from the supply rails and we get a flat spot at the upper and lower peaks of the wave form. In an extreme case, "severe clipping", there is so much additional energy buildup (heat) into the voice coils, but the cone does not move enough to cool the voice coil and former adequately. Hense, the voice coil over heats and either seizes in the gap or burns the voice coil windings. RESULT: OPEN CIRCUIT and you are now sending some DC current to your speakers and this is like hooking them up to a wall outlet and you get a blown speaker.

wingnut4772

Cool explanation.

SuperDave

Wouldn't you hear some pretty fierce distortion when clipping occurs? In other words you can hear when the amp is out of gas and keep it below the threshold of damaging your speakers.:rolleyes:

neomagus00

you don't necessarily hear it... you can clip the bejeesus out of a subwoofer's signal before 90% of people can hear it - i'm talking 15%+ THD... it gets worse if you're using crappy speakers, cause they sound distorted already...

SKsolutions

My understanding from frying more than a few, in days gone by, in a far away place.

You would not be applying DC in a true sense unless the output devices in your amp fried.

If you clip your amp, it leaves out or cuts the extreme high and low of the signal because it cannot exceed it's available current/capacitance, so it "flat-lines" that part of the signal instead of continuing in wave. The speaker is running in AC and following the signal in linear fashion. When the signal flat lines (clips) the speaker is out of linear (position) with the signal. This creates heat as the speaker is forced back against itself to linear with the signal (momentary DC like condition). This would be happing hundreds of times per second -more or less. (There is something to be said about the speakers speed and mass here, but it doesn't really matter, and I don't think I could illustrate it anyway)

If there is enough heat, the former can become mishapen and freeze in the gap on the pole, creating a sustained DC-like situation because the cone now is fixed and coil is "absorbing" the AC current. It also loses all ability to cool itself with movement. Often at this time the coil winding will burn like a filament. This would be the only time you would be left with an open circuit. No AC/DC.

There are situations where you MIGHT not hear it. . . like at extreme volume in a tweeter, although the low moving mass is more forgiving to clipping. . . most subs clip regularly without most hearing. . . . . a sub in a push pull or isobaric setup you may never hear at all

heiney9

Some Sunday reading

http://sound.westhost.com/tweeters.htm

http://sound.westhost.com/clipping.htm

H9