Light Fixture Trips Breaker
The comments pretty much answer it, but the important take away here is that the wire should possibly be replaced.  I was a little thrown by the "speaker wire" comment but I presume you are referring to the light.

Get an electrician in there with a MEGGER to test the wiring. They will determine if it is compromised in areas unseen, and recommend replacing the run if needed.

Be safe! Get the megger. Chances are it melted where you found it, but it could be bad elsewhere, that you haven't found it.