[gpforet]

If the driver is toast, you'll see either 0 ohms (shorted), or infinity (open windings). You're right that anything between 2 and around 10 would indicate that the driver coil is o.k. The reason then numbers can't be exact is that the speaker is rated in impedance (which is resistance to AC and which changes based on the frequency of the voltage), and the ohmmeter measures true resistance (resistance to DC).

Since the person wasn't there, it is possible that the speakers were UNDER-driven with clipped power, and each driver failed individually.