Speakers are rated in watts in order to tell you how much electrical power they
can dissipate. Over 95% of the power delivered to a loudspeaker is dissipated as
heat by it's resistive element and can quickly barbecue the voice coil. Reactive
power (V-A) is what does all the work in a speaker. Since the reactive power is
not converted to heat, the maximum V-A delivered to a speaker will vary
depending on several things such as enclosure type, signal frequency, and driver
x-max among others. In this case the driver will reach it's excursion limit and
mechanically destroy itself.

Since your average loudspeaker is only about 5% efficient at best, it's
satisfactory to only provide it's maximum power rating in watts. If a speaker
bottoms out it will sound like crap and the listener will turn down the volume.
This inherent "built-in protection" protects the speaker from mechanical damage
resulting from excessive V-A.

Kevin Murray

wrote in message
...


True, and I've always wondered why it's not explained that way more
often in the first place. I used to see that "halving the impedance"
crap all the time too, when the correct explanation is so much simpler
- you double the voltage swing, which quadruples the output power.
(Obviously, the *total* power only doubles, since you're going from
two channels to only one when you bridge the amp.)

Liz - I'm saddened to hear that the JL techs were arguing with you
about how amp bridging works. I can understand it if the marketing
types were confused, and maybe even the manual writers, but the techs
and engineers should know better. How hard is it to understand that
power equals voltage squared divided by impedance?

Scott Gardner



Power does not equal voltage squared divided by impedance..... sorry,
but power equalss voltage squared divided by resistance...

impedance and resistances are different...

If you wanna be talking about impedences...you gotta take into account
PF angles... which means you arent really dealing with Power anymore,
your dealing V-A (volt-amps). Just what i gathered at Electrical
eng. school.

Never did understand why speakers are rated in WATTS and impedences.

Can anyone explain this to me? Or is the 5 text books i spent ,which
seems to be, unlimited hours reading...wrong?