Question I Have Never Seen Before?

Buy some really sturdy Uhaul boxes like "dish pack". I cut them completely in half lengthwise. Wrap the speakers in pounds of bubble wrap and then assemble the boxes with a couple of pounds of tape. Cutting them in half allows you to squeeze them to fit.

Call your local crating company they usually carry double walled boxes. But beware, I would not ship something like that unless they are small. Thats just crazy and risky.

I would buy a roll of shrink wrap and wrap the living crap out of them and put the shipping label on it before tryin to do boxes. I have done that before.

I shipped heavy Reference 3As (in boxes) by Greyhound once. Worked well and was cheaper than FED/EX or UPS.

Call the speaker maker and ask to purchase boxes only.