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

@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.

Provided a high power amp source with multiple times the output of a quality speaker’s power handling capacity, it would usually take quite the beating for longer durations for the speaker to actually fail thermally and/or mechanically. Before that happens there’d be sonic implications going from dulled dynamics to outright strain and severe mechanical distortion, and if in the meantime one doesn’t identify these signals as warning signs, well, then I’d seriously question that individual’s ability to assess sound in a fairly skilled manner. Misuse of one thing (incl. what can lead to  all sorts of accidents, some of which are already mentioned in this thread), but unless we’re partying all night with our brains shot without any care in the world for the equipment used (not to mention our ears), most of us around here under more controlled and sober conditions should be able to properly assess when it’s time to ease off on the volume control and call it a day.

Really, it’s not that complicated. How many amps are there in the kW’s range? Buy whatever you like that fits your sonic and SPL needs, and if it means going with an amp that has more power than the speakers rated power handling, don’t worry. On the contrary, I’d worry less, because all things being more or less equal and provided again some common sense use, that amp should perform more effortlessly and with lower distortion at a given, higher SPL.