Hi Dan!
-> You will probably get many responses to this message.   The
-> total resistance includes the voice coil wire plus impedance
-> relating to capacitive and inductive reactance.   These result
-> from the way voice coils, crossover components, and enclosure
-> type  change reactive values based on frequency.   For example,
-> the inductive impedance of the voice coil rises with frequency.
-> Taking all of these sources of resistance into account produces
-> the ohm value cited by a speaker manufacture.    Because of
-> changes with frequency, a nominal(a form of an average value)
-> resistance is chosen.  As a rule of thumb, the voice coil
-> resistance plus 25% is a ballpark figure of the nominal value.
-> But this means, of course, that at some frequencies the value is
-> below or above this average.
Good simple, easily understood way of putting this, Dan! I was planning
a much more long winded discussion on this, which is now totally
unnecessary!
I was getting concerned with the DC resistance messages being equated
directly with the impedance (AC). Ohmmeters are best used to check if
the voice coil has a complete circuit or has been broken, but is not
otherwise directly related to impedance except as your rule of thumb
stated above, which seems to be true from my experience, also.
.
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