How to pack speakers w/out original boxes?

Use the 2 and/or 4 inch round foam noodles especially in each corner. They are usually sold in 4 foot lengths, and can be cut to size across or in half lenghtwise. Use them and double box even if you have the original boxes.

If you know how to pack, you can make boxes stronger than the originals. It takes a little time, but you can use thicker and better foam sheets, cut round foam noodles for the corners and line the second box with protection also. I always keep the original boxes for everything, but I also add protection to the inside box and use an outer box on top of that. Pass on or split the shipping with the buyer. Better safe than sorry.