Again , depending on size and if you want to do it yourself , this is what has worked for me many times shipping average sized floorstanders .
1.) Go to U-Haul and get two of their wardrobe boxes .
2.) Go to Home Depot and get a couple of packages of their styrofoam insulation sheets , they are 16" X 48" X 1" . They do have 4'X8' sheets of thicker strofoam if you need it . I prefer the styrofoam packing over cardboard because the styrofoam will not absorb or pass water if the outer box gets wet .
3.) Get a roll or two of heavyduty packing tape , clear .
4.) If needed get some very large heavyduty trash bags .
Put the speakers inside the trash bags and seal with tape . This is for moisture control .
Depending on size , line the bottom of the wardrobe box with strofoam and put the speakers inside . Now fill the rest of the space up with the strofoam panels . Make sure everything is as tight and filled as possible .
If you have the original packaging use it and then put inside of the wardrobe boxes . This will be a double packaging and more protective .
Tape everything closed and tape over all seams and junctions . You don't want any available openings anywhere . Also wrap tape around the sides and around the top and bottom . Sort of like banding straps .
Make address cards , I use 5x8 note cards . Put a couple on each box and cover with the clear packing tape .
I like to ship with FedX "Red" , not green . It costs more but they exhibit much better handling of their packages !
And of course make sure that they are insured !
I have used these procedures for all of my eqiupment shipping and have had zero damages to the merchandise !
Good luck.