[Don Pearce[_3_]]

On Fri, 26 Apr 2019 12:15:14 GMT, (Don Pearce) wrote:

On Fri, 26 Apr 2019 05:01:41 -0700 (PDT), wrote:

Don Pearce wrote:



A true RMS current meter doesn't help, unfortunately. A speaker's
impedance is very reactive so multiplying RMS current and voltage
doesn't give you power.



** Of course, but what you actually do is multiply the rms noise current SQUARED by the voice coil resistance to get the heat dissipation in the copper wire in watts.

If you find the minimum impedance of the driver with a sine wave test in the mid band, then that number can be used instead of the copper resistance to give an accurate power dissipation figure, including suspension and eddy current losses.



That would need some sort of measurement
system that could provide vector products. As for doing that with a
noise source, forget it.


** A wind band power meter will do the job, analogue multiplying or digital sampling.



So no, you can't measure pink noise power into a speaker.


** Of course you can.



.... Phil



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.

And just so you understand, I used to design measuring equipment for
Marconi Instruments. I hold patents for measurement methods and used
to have a NAMAS accreditation on an individual basis.

d