Kind of on the first half, no on the measuring part. You can't measure the impednace with an ohmeter, only the DCR. To measure impedance the system has to be under power (can't test with an ohmeter with anything else connected to the sub) and you must either due this with an impedance bridge, current vs. voltage (not very accurate using cheap meters), a specific measuing device (Dayton woofer tester for example), etc.... Also, you can't ever wire up your subs to .5 DCR. The DCR will always be lower than the average impedance. For instance, if yuo have a sub with a nominal .5 ohm coil, the DCR will be lower, say .4 ohms, even lower maybe. Theoritcally, at some frequencies, you might be right down near DCR, so your .5 ohm sub could be presenting your amp with a .4 ohm or less load. Remember, when manufacturers spec out an impedance for a sub, it is an average....