Lena,

It's kind of hard to answer a question like this. The most obvious answer would be to look at the rated power handling of the speaker. However, as with most published specs on consumer electronics, it's probably way overrated.

There are a number of things that can blow up a speaker. You can overheat the voicecoils of the drivers, which can literally melt down the wire, causing shorts. The heat may sometimes melt the glue on the voicecoil former, which then binds to the magnet assembly, and locks up the speakers. These would all be considered "thermal" power handling issues. Most often this is the rating used for a speaker.

The other way speakers typically blow is from over excursion - that is, the cone/dome moves in or out further than the driver can handle. This can happen on both tweeters and woofers. Excursion is related to frequency, such that, the excursion necessary to maintain a constant SPL increases to the power of 2 or 4 (can't remember which). But basically, the lower you try to play, the bigger and bigger the physical demand on the driver's suspension parts (spider, and surround, mostly). If you start throwing the cone/dome in and out really far, the voice coil or voice coil former can actually "bottom out" and slap into the back plate of the driver and physically deform the voice coil. If you smack it hard enough you can mangle it enough to permanently destroy it.

I think it's fairly well accepted that there is a lot more energy in lower frequency material.

Now on to the matter of clipping vs. distortion. Clipping is actually a form of distortion. Distortion is anything that changes the original signal. To put it bluntly, speakers are distortion machines! Of all of the things in your audio chain, the speakers mess with the sound the most. The perfect loudspeaker would recreate the input signal exactly, and that's not even close to the case.

To visualize what the different kinds of distortion are, think of a sine wave. Looks nice and smooth, with peaks and dips. Now chunk off the tops and bottoms of those waves, leaving a flat line. That's clipping. It happens when the amplifier runs out of voltage. The effect this has on a speaker is presenting it with something like a square wave. Some would argue that this is the equivalent of giving the driver +DC and -DC voltages. That's sort of true, but the reality is that it is a bunch of really high frequencies laid on top of the original. Ok, way to technical there. Anyway, it's bad for your speaker because it suddenly throws way more energy at it that it was dealing with before. Lots of times that's what blows tweeters, but it can be equally bad for midrange and bass drivers as well.
Compression is a method for dealing with clipping. Rather than chunking off the top of the wave, they squish it down so it still fits within the amp's voltage limits. Basically, you end up suppressing loud peaks. Compression is actually a good thing for your speakers, keeping them from the nasty clipped signals. To your ears, it's not such a great thing, as it can substantially mess with the sound.

Now, how do you know what speakers are going to be good? That's even harder. Unless you are able to take the speakers completely apart or know the specific drivers being used (and just as importantly the crossover points and slopes) it's really hard to guess what's going to live longer than another speaker. Unfortunately, the only thing a manufacturer is likely to provide you with is an RMS/Max power handling rating.

Now, to keep your speakers from blowing up, here are a few things you can do. Make sure that the amp you are using is putting out clean power. Oddly enough, using a really big amp that puts out more power than your speakers are rated for isn't necessarily a bad thing. Just make sure you use self restraint. This will avoid compression and clipping. Also, when you cross your speakers over to a sub, make sure the crossover point is sufficiently above the lower limits of the speaker's frequency response. This is particularly important for ported speakers. Below the port's tuning frequency, the woofer's excursion rises very rapidly, and can cause bottoming with only a few watts in some cases (at very low frequencies). If your speakers are sounding "strained" at all, you are probably feeding them with either too much power, or an unclean signal, either of which will probably kill your speakers prematurely.

So in conclusion, I don't have an answer for you, other than your only really safe bet would be to buy pro sound speakers, in which case you could hold a rock concert in your living room with complete peace of mind.

Jason

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