How do you know if you have blown your voice coils. I have 12 inch DVC subs. They used to sound real nice and loud. Now they dont sound half as good. I mean they still work ok but its just not the same sound I had. When I hook them up to the voltmeter the reading fluctuates.
I dont think its that, you would be able to really for sure tell if the coil was snapped. I mean the sub would be very scatchy and rought. I blew on of my coils and the sub froze up, it didnt even move. I think there is something not hooked up the same or a eq setting.
If the coils are in parallel and you're running bridged on 8+8 ohm DVC, with two you're putting a 2 ohm load on a bridged channel. Doesn't sound right, seems like the amp would go into protection. Double check that, if it doesn't solve the problem, make sure the wiring is right and, like said above, push on the sub's cone and see if you hear a scratchy sound. Also check individual coils like Michael said, not just the final load.
Probably 9 times in 10 you can identify an open VC by just pushing down on the cone and listening for that horrible scratch sound. If you don't find anything out of the norm like this, check each coil with an ohm meter.
When the coil 'opens' up, it usually comes loose and rubs against the internals of the motor structure...that's your scratch sound. Sometimes, however, the coil can stay 'tight' but still be open. There are various coatings, wraps and the like that are sometimes applied over the final VC assy and this can hold the coil together even with an open circuit.