Quote Originally Posted by tony3d
I'm am unclear how to match a power amp to a particular speaker to get the most power without endangering the speaker. I know it's much better to use a high powered amp than an under powered amp, but how do you know when you have exceeded safe reserves? Say your speaker is rated at 250 watts RMS power handling, they could take much more peaks, so would you be safe with say 450 watts to make sure you don't clip the peaks? Is there a formula to figure this all out?
Not to detract from Kex' more in-depth explanation, maximum speaker ratings are irrelevant in home application. You would never, ever listen in your home to speakers putting out 250 watts RMS, or even 100 watts RMS -- that would be insanely loud.

I gather it's true that severe or continuous clipped signal is very bad for a speaker, but bear in mind that severely clipping will be quite audible and you will presumably reach for the volume control very quickly to get rid of it. In home practice, the symptom of an under powered speaker is a compressed, non-dynamic sound at higher volumes versus lower volumes, it's not the frank distortion you hear with severe clipping.

I would say be concerned to avoid a compressed sound at the highest volumes you normally listen to. This will depend on the qualities of the speaker as well as the amp, but will have only a loose correlation with the speaker's maximum power rating.