On Wed, 14 Oct 2015 20:11:26 -0700, Phil Allison wrote:

wrote:



OK - a few basics on speakers - at least as they were sold in the US
under FTC regulations (sit on your fingers, Phil!):


** The are simply no FTC rules for published speaker power ratings. The
rules you seem to be alluding to are for *amplifers* used in home
entertainment.


c) Low cost, low-wattage amplifiers are much more likely to cause
speaker damage than large amplifiers.


** Depends a lot who is using the amplifer - but in general the risk of
speaker damage goes up with more amp power.


What can happen with some solid-state designs is that when the
amplifier clips (called to produce more power than it can),
it may send straight DC into the speaker

** Absurd.

Clipping does not cause DC, the main effect is to compress the dynamic
range of the music so there is more average power going to the speaker -
which eventually overheats the voice coil.


This issue is far less so from a tube amp - the simplistic explanation
is that it is harder for a transformer to pass DC,


** Impossible in fact, but clipping wave peaks is just what tube guitar
amps do most of all the time and blown speakers are very common - due
again to high average power levels.

Makes sense the way you've explained it, Phil. I had a Technics amp one
time that just ate through speakers for some reason; all top quality KEF
units as well. The only thing I could come up with for a cause was
that the amp sound was very 'cold' - typical of Technics amps - so may
have been producing transients the speakers couldn't handle. But that's
no more than a hunch.
The other thing the OP seems to be unaware of is that the term 'RMS
power' is really indefinable anyway. You can't take the product of RMS
voltage and RMS current (which are both valid measurements) and derive
'RMS power' from them. We should drop the use of this non-sensical term
and adopt 'average power' instead. And as for 'total peak music power' -
bah! Don't get me started! ;-