[RodB]

You can center the voice coil using 4 long 1/4 inch strips of paper placed in the gap opposite each other, then slowly drop the vc into the gap. If it's too tight to give you some cone movement use thinner paper. Make sure the voice coil wires are in the correct position for the OT. When you have some movement then secure the cone and pull out the strips. I just did one and was very satisfied with the results.