Originally Posted by vjarnot

Speakers fail in two ways:

You turn the volume to a particular level, which determines the load that the speaker places on the amp, let's say X watts.

Now then: your amp either can, or can not, supply X watts:

a) your amp can supply X watts: the speaker plays at the selected volume. If playing at this volume causes the speaker to exceed its thermal or physical capacities (i.e., the amount of heat it can dissipate, or the distance the cone can extend), then the output sound is distorted and the speaker ultimately fails.

b) your amp can not supply X watts: the amplifier attempts to supply the amount of power that the speaker is drawing, but can not. This causes clipping, as the electrical waveform from amp to speaker has its peaks and troughs squared off. The output sound is compressed and the speaker ultimately fails.

The key bit that many people don't get is that the speaker is the component that determines how much output power (i.e., wattage) is drawn from the amp.