"MZ" wrote in message

Okay, let's look at this problem slightly differently and see if it
makes more sense.

When a small amp goes into heavy clipping it produces a signal that
looks pretty much like a square wave. Forget about the harmonic
train for a moment and just look at (or consider) the shape of the
signal: a sudden rise to the top, it
stays there for a while, then a sudden drop to the bottom, where it
stays for a while, and then it repeats all over again.

There's another way to describe that kind of signal: pulsating DC.
For a speaker, it's a hard signal to handle. The speaker moves out
and simply sits there, then it moves in, and sits there. While it's
just sitting there, being held out (or in) by the voltage, the
temperature in the voice coil is rising, since there's no way to
dissipate the heat from the "DC" that's holding the
speaker still. Do that long enough (even at lower than maximum
speaker ratings) and the coil will eventually burn up.

Is that easier to grasp?

Unfortunately, it doesn't really clarify anything. In fact, it
muddies things up even more. First of all, there's not really such a
thing as "pulsating DC". That's an oxymoron. If it's "pulsating",
it's by definition an AC signal.

Your skepticism is IMO well-founded.

When you cleanly clip a music waveform, it doesn't just look like a square
wave, it is a variable-frequency square wave. However, there's no guarantee
that a true POS power amp will clip cleanly. What this comes down to is that
a POS is a POS, and using a POS power amp can be dangerous to your system,
no matter what its power rating is.

If we drop the POS power amps from the discussion, we're left with what
happens with a competent low power amp as opposed to what happens to a
competent high powered amp.

To understand this better, you have to consider how speakers fail. IME the
most common form of driver failure is caused by overheating of the voice
coil. Second is fracturing of the voice coil wiring due to excess flexing. A
third failure mode relates to over-travel of the cone. These three most
common loudspeaker driver failure modes have a common cause - too much
power.

Much has been written about spectral shifting due to clipping, and this can
clearly stimulate the first and second modes of failure by causing more
power to be routed to high frequency drivers.

However, there's a lot of music around whose high frequency spectral
content actually decreases when it is cleanly clipped, and even more where
there are no appreciable changes.

Classical music is one genre where upward spectral shifting can still be
dominant, but even there it's not a sure thing. During crescendos crashing
cymbals and blaring horns can build up a lot of power at high frequencies.

The bottom line is that most of the failure modes of drivers come from the
driver receiving too much power, too long. The easiest way to get more power
to a speaker is to have a more powerful amplifier. These days, 100 wpc power
amps are unbelievably inexpensive. 100 wpc is a lot of power for most
consumer speakers to handle, long term.

Intensely powerful *accidents* are more likely with more powerful
amplifiers.

More powerful amplifiers also provide a psychoacoustic cause for speaker
damage. Undistorted music often sounds less loud than distorted music with
equal power. Therefore, a listener is more likely to apply more power to his
speakers with a more powerful amplifier. In the absence of clipping, the
music will not sound as loud as it will if it is clipped.

That all said, I have just a few kilowatts of power amps around the house,
and most of them are hooked to speakers. The good news for my speakers is
that I have a lot of fairly robust speakers, and I try to be careful.

I don't think there is any doubt that over the past 30 years loudspeakers
have become as a rule, more robust.