To use a DVC properly both coils should be wired (either in series, parallel one amp to each coil). Otherwise you are not getting the subs full potential. Using one coil can cause premature failure as well (no comments Dave
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It is possible to have one coil of a dvc to go bad under normal use, once this occurs the woofer must be replaced.
The idea behind a dvc is flexiblity, it does not mean you can blow out one coil at a time till all of them are cooked
