If I measure the DC resistance of an assembled HF driver will it be different than the DC resistance of the diaphram when it is not mounted in the magnet?
I have some HF drivers that are measuring 12.1 ohms but my supplier has raw diaphrams that are measuring about 6 ohms. He says his are 8 ohm nominal diaphrams. Mine I believe to be 16 ohm versions. I do not need a diaphram but I just want to verify just in case I need to replace diaphrams in the future. Of course I have 12 years on the boxes without issues so it may never come up but you never know.
Thanks a bunch, Ryan
The general formula for impedance is -
Z = (( R
^{2} + (X
L - Xc)
^{2})
^{½}When you measure the DC resistance you are only measuring the R bit. You are not taking to account the reactance … the X bits
Xc = 1/(2pi FC)
X
L = 2pi FL
Soooo the Z for a speaker is always a bit more when you add the bit that comes from the inductance / frequency.
Note - the inductance is effected by the mechanical behavior of the driver - that why there are peaks and dips in the impedance curve associated with mechanical resonances.