And so it came to pass, on 10-06-96 09:55,
   that John Allen spake unto Dan Dunfee:
 JA>         For years I have read and heard many people say that more
 JA> loudspeakers are damaged or ruined by underpowered amps than blown
 JA> out by overpowering the drivers. I had come to accept this as fact
 JA> after hearing it so often. The "control" exercised by the higher
 JA> powered amps usually came up during the conversations and in the
 JA> article(s) as well.         Now that I have read some of the
 JA> responses to my repeating that in the Echo, I have to question it.
It's got less to do with control and more to do with distortion.
Imagine you have two amps -- one puts out 50W across an 8 ohm load; the other 
is capable of putting out 500W.  The 50W amp may have voltage rails that 
operate at around +/-20VDC and a fairly limited current supply; the 500W 
amp's rails may run around +/-60VDC and have the capacity to deliver much 
more current.
Now suppose you give each has a gain of 100, and you feed each a signal that 
peaks at +/-400mV (.4V).  In a theoretical world, the output stage of each 
amp would need to produce 40V peaks.  The smaller amp, however, would max out 
at 20V.  As the signal goes above 20V, the actual output remains constant at 
20VDC until the signal drops back below 20V.
During this period, the speaker is being fed 20V of pure DC power.  There 
will be some mechanical damage caused by the speaker being pushed to one 
extreme and held there for that duration of time, but even more importantly, 
the voice coil, which is designed to withstand only very brief peaks of 
voltage and which relies on its movement for cooling, will heat up very 
quickly. 
This leads to numerous potential problems: the coil can simply burn out and 
go "open"; it could burn off the insulation between windings and go "short"; 
the coil could warp or the insulation bubble on the outer layer and cause it 
to start scraping inside the gap... 
Meanwhile, the 500W amp continues pumping clean power through -- the 40V 
peaks are too brief to cause any damage, and the cone is always moving so 
it's always well-ventilated.
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Q: Why don't blind people skydive?
A: It scares the heck outta their dogs!
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