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Don Pearce wrote:


Nope. Didn't understand a word of that.



** Really ??

So " I squared R " has no meaning in your world ?

The resistive losses that increase a speaker's mid band, resistive impedance beyond the DC ohms value are also mysterious to you ?

A multiplying power meter, using analogue multiplier ICs, is also a mystery ?

Where have you been hiding Don.

Under a rock?



.... Phil

I squared R has plenty of meaning. Unfortunately a speaker is not an
R. It's an X. And I squared X gives you VA, not Watts. Your
measurement method, applied to a pure capacitor, would apparently
yield a power level. You can't put any power into a capacitor.

d


Oops - let me correct that. A speaker is a whole slew of different R +
jX, with the values being different at every frequency over the
measurement band. No scalar instrument can tell you about power
transfer into that. You can do it with a vector instrument at a single
frequency - and I regularly do that.


But a noise signal with a scalar voltmeter and a scalar ammeter? Nope.
Not on this earth.



** You are making a very basic mistake.

Consider the following:

If you apply a noise voltage to a resistor and measure the current flow with a wide band, true rms meter the formula "I squared R " applies exactly.

If you add an ideal reactance in series with the resistor the formula "I squared R " still applies since the resistor is the only power dissipating item.

A speaker can be accurately modelled as several resistances in series with a lossless reactive component, also in series. My earlier post outlines how to quantify the additional resistances due to suspension losses etc - works out to be about 20% more then the DCR value of the voice coil.

So, power dissipation IS "I squared R " where I = the rms current flow and R = the resistive, mid band impedance minimum.

BTW:

You really need to check out how multiplying power meters work.



..... Phil