I can't find a box to ship my speakers,,,,,,,,,,,,

Think "outside the box" and hire a carpenter...

Most Mail Boxes etc and other packing stores have people who crate for them, I wouldn't recomend using them to ship as they are expensive, but with a little tack you might find out who makes their crates.....

I have had really good experience with www.associatedbag.com
They have a lot of shipping supplies. Not sure about your particular size. But they have been great to work with on the phone, and very quick too. I needed a sample to verify my need, called on Friday, it was on my porch Monday. I have compared prices, and they were the cheapest too. Another option is your local U-haul should have these boxes they call "mini-wardrobe", which are quite large and could easily hold a large speaker if packed appropriately. They are around $7 each.

Use a carrier and send them as a "pallet" shipment. Most major carriers, even moving companies will do this. It isn't cheap but neither is UPS. That way, all you have to do is cover them with a packing blanket and strap them to a pallet. A fork lift does the rest?

Anyone here have a degree in fork lift driving? Neither do the guys that drive them. I've had enough stuff damaged IN boxes when they were strapped to a pallet that I'm not real comfortable with that one.