A speaker rated for 85/340 W has some assumptions about the overall spectra of the input signal resembling that of music. If its all above the crossover point, and you put it all in the tweeter, you will blow the tweeter, your ears, or both, real fast, for the vast majority of tweeters. If the crossover has some attentuation of high frequency in the response curve, you may blow the crossover as well, although the tweeter will probably protect it. Clipping is a non-linear operation that will put a lot of power into the high frequency band.
John
I understand that, but...
I built a couple of low power speakers (below 60W max) and looked at many designs before settling on one. Out of curiosity I looked at the specs of the tweeters used in those designs. Pretty much all tweeters I looked at could handle more than 40W continuous (only one specified the frequency as 6KHz, so definitely frequency can influence). The amplifier in the original question was 22W max. Even assuming that only high frequencies exist and the crossover is a perfect crossover sending all the power to the tweeter at the maximum amplifier power, there is sill a significant margin of safety
Now, granted, there are no specs for the LTS 1" tweeter used by the Klipsch speakers, and it's a horn loaded tweeter, so it's entirely possible it can't handle as much. But an 80W continuous speaker must be able to handle 80W of a 22KHz signal without too many problems. People routinely play speaker calibration CDs at high volumes, and those frequencies are common. And the max rating is still 340W, so there is a margin
I have a hard time understanding why, in this specific situation, using a 20W amplifier, even with clipping, can be a problem. "Area under the curve" doesn't explain it, nor higher harmonics. And, yes, clipping is non-linear and generates a ton of harmonics, but it won't generate a continuous 22W 40KHz signal dumping 100% of the power available into the tweeter.
In general, I understand perfectly how a poorly designed lower power amplifier might damage a tweeter. But I simply cannot see how in this specific scenario (22W amplifier of decent quality, hence low-ish clipping, 85/340W speaker) is a problem