How do you know if your speakers have been damaged due to clipping?
usually you can hear some distortion due to the voice coil being fried. it will be most noticable on louder passages with bass. you will hear what sounds like scratching or it might sound like little to no bass response.
While amplifier clipping is most likely to occur as a result of high volume bass notes, the resulting speaker damage is most likely to affect the tweeter.

That is because the abrupt discontinuity in the waveform that occurs at the clipping point contains abnormally high amounts of high frequency energy, that is not present in the original music waveform. That high frequency energy will be routed by the speaker's crossover to the tweeter.

So the first thing to check would be if the tweeters are working at all, which you can probably do simply by placing your ear in front of them with no music playing, and listening for low-level hiss (turning up the volume control if necessary). Beyond that, listen for any abnormalities in the reproduction of high frequency notes.

It might also be a good idea to look at the woofer cones and surrounds for tears or any obvious physical damage. That would not result from clipping per se, but can result from their being over-driven.

-- Al
Tweeters usually fried and silent or audibly distorted as described above.

Other non speaker problems might sound similar. Hook the speakers up to some other source and listen for the problem that way first if possible before drawing final conclusions.
If you have it, Peter Gabriel's "So" contains a great test track that I've used to identify a clipping-damaged tweeter (been there, done that, more than once). Check out Track 8, "We Do What We're Told". No need to listen to all of it...the opening measures before the lyrics will tell you what you need to know. If there is damage to a tweeter, you will hear a scatchy obviously distorted sound. You'll know it when you hear it. If it sounds lyrical and far, so good.
Thanks for the info. I downloaded the track from iTunes and it looks like all is well with my speakers, it sounded good.
Great...I should have added, listen with your ear quite close to the tweeter(s) to hear the distortion. When I had a problem the sustained instrumental notes and choir voices in the intro would break up at moderate volumes. But I really needed to be close to hear the "buzzing", as I recall.