You are measuring the DC resistance, what you would want to measure is the impedance at some frequency. When you have capacitive or inductive elements (like a transducer coil) in a circuit, the resistance for AC will be drastically different to the DC resistance (and it will have a frequency dependency, this is what is called impedance, and it is in general a complex function, complex as in complex numbers). Additionally to the purely electrical domain, the physical properties of the entire setup will also have a strong influence on the impedance. Physical resonance frequencies of the transducer can be seen on the electrical impedance.

For loudspeaker transducers, the impedance that is stated in the spec sheet is usually measured at 1kHz. Does the manufacturer specify the frequency at which they measure the impedance?

For reference, this is what the impedance magnitude curve of an exemplary loudspeaker looks like. Your buttkicker will probably have a qualitatively similar curve, just differing numbers.

One way to measure the impedance at a certain frequency is to apply a sinewave with the wanted frequency to the transducer, then measure RMS values of voltage and current. The impedance at the frequency can the be calculated with Ohm’s law:

R=U/I

All that being said, if the DC resistance is actually 0.001Ω, then that seems unusually low.