I've recently been checking out some higher end cans and some (I can't remember which) contain aluminum voice coils. This seems slightly strange, since aluminum is definitely not as good of a conductor as copper or silver, and given that the voice coil is designed to create and respond to a magnetic field, it seems like an aluminum voice coil would do a poorer job, even after considering its inherent lightness. Is it used in conjunction with copper to create a more rigid and light voice coil? or am I totally off? This question's purely out of curiosity.