Ok, resistance. Tomato tomatoh. Look in the magazine specs, speaker description shows "nominal impedance", which I check by measuring with a VOM set to "ohms". Then I can talk about the "resistance", which I've called "impedance" my entire life including when I'm talking with audio engineers, but apparently I've gotten that wrong and no one thought to correct me until now.
The point is, I set this meter to ohms, I measure across the speaker terminals. Doing this for decades across many different brands, and no matter whether it was raw drivers or complete 2 and 3 way boxes, I would get a value between 4 and 8 ohms. I have other Canton speakers here just under 4 ohms. These are giving back the oddest numbers I've ever seen. Compare it to some others in my stash:
Case#1: B&W speakers, downstairs media room: 4.6ohm
Case#2: B&W speakers, rec room: 4.7 ohm
Case#3: KEF 100, home office: 3.2 ohm
Case#4: Canton LE102, random location: 3.7 ohm
So I know these are nominal "at rest" numbers that don't take into account the inductance changes over frequency, yada yada yada. I've used an ohmmeter to check a speaker out when I buy it to make sure it isn't blown "OL", shorted "0.0" or something weird in between. And this sure looks like "weird in between".
Resistance and impedance are NOT the same thing even though they are both measured in ohms. They both measure the relationship between the voltage and current through a circuit, but impedance also requires that an AC frequency be specified. Resistance does not.
Resistance can be measure using either DC or AC voltage, since it is independent of frequency. In essence you can measure a resistor either way.
A reactive component, however, has an impedance that is directly related to frequency. The impedance of a capacitor at low frequencies is very high, At DC (0 Hertz) the capacitor impedance is infinity, i.e., a open circuit. As frequency increases the impedance of a capacitor decreases.
The opposite is true for an inductor(coil). At DC it is essentially just a resistor. But as the frequency increases so does its impedance. At high frequencies it will not pass much current at all.
These are the characteristics that allow high pass and low pass filters, or crossovers if you will, to be constructed.
Even though your DMM or VOM gives you the ability to measure resistance it generally will not allow you to measure impedance. That's due to the fact that measurements on those instrument are usually done with DC only. You can't measure impedance with DC. It has no meaning in that case.
The reason you are getting erratic readings when measuring across speaker enclosure terminals is due to the crossover between the terminals and the drivers. There is no meaningful DC measurement that can be made across those terminals.
On the other hand, if you disconnect a driver from its crossover, and measure directly across the driver's terminals with a VOM you will read the resistance of the coil windings. This is typically given as Re in specification sheets and measured in ohms.
If you look at those same sheets you will see an impedance graph for the driver that varies with frequency. Again, measured in ohms.
