"Peter Chant"

Isn't the rule of thumb that the impedance is about 1.5 times the DC
resistance - hence measure the good unit and multiply by 1.5?


** The ratio of DC resistance to nominal impedance for a low/mid frequency
driver is usually close to 1.2

This assume the impedance (Z) is measured at 250 to 400Hz ( where Z is a
minimum) and with low power so the voice coil does not heat.

The ratio represents the additional mechanical ( friction) losses in the
driver's suspension, eddy currents in the magnet structure plus of course
radiated sound.



..... Phil