Shipping speakers

Interesting, after the OP asked a specific question, only 5 out of 16 responses actually answered it.

Packing is a big part of not getting your products damaged. Use open cell packing not styrofoam. It is too rigid and does not allow for cushining from impact.  Swimming noodles are excellent and cheap to. I will use styrofoam around the outside and noodles next to the gear.  Minimum 2" to 3" aroind what you are shipping. Dishwaser / appliance boxes are free, you just have to custom fit them. Costco produce boxes are very rigid for things like amps. I sometimes put 1/8" plywood around it.  So far so good with things shipped as far away as NewZealand and Belgium.

Any courier would do that just keep far away from FedEx!

Cost-effectiveness is difficult when shipping heavy units.  Stay away from any shifting packing materials.   

Craters and freight forwarders could be rough on the speakers.

for big heavy studio gear, have used Plycon with great success.
ask them for a quote for their Blanket wrap. They will wrap the speakers in heavy pads, then get tied to the wall of one of their air ride trailers. much smoother than a freight trailer. Link below.

https://www.plycongroup.com/freequote.php