This is pretty good stuff, but I have some other input that might help.
RMS= Really Moronic System (of measurement)
This (RMS) is almost an ignorable statistic. The best stat for measuring
speakers it their CP or Continuous Program capability. This sits (roughly) in
the middle of their power band and takes into account where the manufacturer
says the speakers should be run at median signal (hz) and median power for
maximum preformance. A set of 150 Watt CP speakers will waste a set of 150
Watt (RMS) speakers. The RMS speakers will die from thermal or separation at
around 170 Watts whereas the 150 Watt CP speakers can (usually) handle spikes
in power at around 300 Watts. Remember, audio is a lively bouncy thing that
never stays put and signals that do, tend to damage things: including speakers.
My rule of thumb is to purchase extremely clean amps that are twice the
power of the targeted speakers Continuous Program. If I start to hear
distortion in the sound then I know I am pushing my speakers too hard and can
back the volume down, as the amps only put out distortion at a power level
higher than the CP of the speakers. In this manner I don't risk the speakers
or the amps to blowout.
There is no hard and fast rule for converting RMS to CP... if the
manufacturer doesn't have a CP rating for the product, you may want to
consider going to a higher classed product or a better manufacturer.
Sometimes they hide the CP ratings in the speakers vital stats area.
Shaun H.
---original message---
While it is possible to blow speakers from too much power (actually
tearing the cone from the spider), it's extremely difficult. However,
it's way too easy to blow speakers from too much distortion. Distortion
is measured in % of THD (Total Harmonic Distortion) at a particular
wattage output. Lower is better, preferably .1% or lower. When shopping,
I TRY (but don't always succeed) to get an amplifier that equals or
slightly exceeds the power rating of my speakers (both in RMS, of course),
with very low distortion. If you go lower than the rated output of your
speakers (assuming a quality amp), just make sure you don't have to turn
up the amp too far. If gain must be set above about 5/8 or 3/4 to get
sufficient output, you have an underpowered amp. The closer you get to
the top of the gain knob, the more distortion. The very best systems run
with the gain at the lowest setting (turned counter-clockwise all the
way). Mine doesn't, because I'm cheap (it's around 1/2 of maximum). My
two indian-heads.
David Gloff
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