Can a power amp have too much power, risking damage to a speaker?

Note that any tube guitar amp from a 5 watt studio amp to a 100 watt whatever will often be used overdriven with distortion into the speakers for DECADES with no harm done. If people are lame enough to drive their delicate little home stereo speakers to the edge with a high powered amp (especially a solid state one) there's little to be done for them.

As pointed out in one of the threads, when the maximum power of an amp is reached, the distortion rises very quickly. It is a "bell" curve rise. The distortion goes from "zero to a hundred" really fast (smallest movement of the volume control), and the distortion created plays havoc with the tweeter/s and midrange speakers.

Not so much with a group like this, but what I saw with the "how loud will it go" crowd was, they "cracked it" and after a while the tweeter went. Five to ten percent of the sound was lost, so they "cranked it" again.  A short time later there was less sound again because the mids were fried.

Woofers pretty much have to be abused with brute over powering or "bottoming" them out with excessive bass and power. I had knuckle heads complain that their speakers were  making a "whip cracking" sound, or a "blatty" sound. As it turns out, they have the loudness button in, bass control cranked to the max, and  the volume control at 3:00 (because that's only 3/4's of the way up, it should be able to do that).

In my experience, less than 5% of the time did speaker repairs result in a woofer failing.

To go along with that, I saw more blown speakers caused by them being under powered, than over powered, and that goes back to how the distortion increases when full volume is reached..

As for the guitar amp being over driven, in most cases you are dealing with a speaker that is basically a woofer. The distortions being generated by the "stomp boxes" are in the mid and upper range frequencies. This is not really taxing or putting the speaker in any danger. 

I have a pair of B&W speakers that have a recommended power of 50 to 300 watts. I'm driving the pair with a 120 watt tube monoblock amp attached to each. Other than having to chase down a ground loop issue (which I solved the other night), this setup is flawless. It may be "underpowered" but sure does not sound like it. I may build two more monoblocks and Bi-amp the speakers, for now, I have no need and it sounds amazing.

@joelepo wrote:

I have a McIntosh 402, rated 400 watts continuous per channel. If I use it to drive a pair of Klipshorns or LaScala [specified to handle 100 watts continuous] or similar high-efficiency speakers, do I risk damage to such speakers?

The La Scala’s are just around or slightly above 100dB’s measured sensitivity, and so would be very loud even with limited power supplied by the McIntosh; practically you likely won’t get to where your speakers are challenge thermally let alone mechanically, whereby the power in reserve will come in handy with loads of headroom (which is a good thing). However, something tells me the La Scala’s thrive on tube-based amps, preferably moderate to higher powered variants, so that might be worth experimenting with.

With inefficient and passively configured speakers in general (and most are), I’d recommend at least double the amp output power of the speaker’s long term max. power handling capacity. Less SPL requirements/shorter listening distance/more lively damped rooms can do with less amp output power.

Efficient and typically passively configured speakers of yore/vintage origins or inspired (with lower to moderate power handling) seem to thrive on and get by with low powered amps, tube-based in particular, whereas more modern and pro segment high efficiency speaker designs with larger voice coils and stiffer suspensions like to be fed by high powered SS amps - they simply come better and more assuredly to life this way, not least actively. Both approaches have their strengths; the former can come across seemingly a bit more lively and with more character, while the latter has the more solid and, to my ears, "neutral" and resolved imprinting. I prefer the latter camp for a variety of reasons, but I can appreciate either approach.

Thanks all for contributing to my education.
I play guitar and 5-string bass and have one Fender Pro tube amp with twin 10" speakers and a Fender SS Bassman with four 10" speakers. Guitar amps and speakers differ from high-fidelity amps and speakers. The former are designed to "produce 'music'" -- so as long as they hold together and generate the sound the musician want, all is OK. In contrast, seems to me that "high fidelity" speakers should not contribute any of their own voice to the sound that comes out. I KNOW... achieving that ideal is far more complicated than that.