Recommendation for packing/shipping large speakers

No good substitute for packing yourself. That way you know just how well they were packed.
Now as for materials it depends how large.
I am assuming you no longer have oem packaging by your question to begin with.
Both ups and FedEx sell what they call a golf club box. This is perfect size for a lot of speakers and I consider the ups one to be a bit thicker and stronger. Cost about $20 each. Buy bubble wrap etc from Wal-Mart, lot cheaper!
I also use polystyrene packing inside but I am a packrat and usually have lots of stuff useful squirelled away.
I tend to wrap speaker in bubble wrap and then many wraps of clingfilm/ shrink wrapping film again from Wal-Mart.

Well, the speakers are 60 lbs each and measure 43" x 16" x 12". I don't have the original boxes- got damaged in storage during hurricane.  

Then the ups golf club box is perfect size, buy direct at any ups store. 
Wal-Mart for bubble wrap, cling film, peanuts, maybe packing paper too.
I have shipped many speakers I sold here and eBay using same method.
Last ones were b&w 804d.
All arrived safely.
I wrap the speaker first then slide into the box or slide box over the speaker. Lots of packing once in the box to stop it moving around.
You have to make it so the only way they could damage it would be to run over it!
Also lots of fragile and handle with care signs on box too.
Not sure if they take notice but in event of damage it helps your cause on any claim!

Call the manufacturer, you might be able to buy original boxes & inserts from them. 

mrboxonline.com will sell you custom made boxes and packing materials very reasonably priced. I purchased double boxing, sized to order, for very large Dunlavy SC-IVa’s I sent to England. 

That is useful to know ncarv, filed away for future reference
Thank you

Plycon is a vanline that specializes in feagile and high value items (think priceless marble statues or paintings).  They pick-up with a white glove service, pack, deliver & unpack, all the while your item is completely insured.  They’ll even deliver inside and place on position.

Wrapping each speaker in the Pink Rigid  Polystyrene Insulation available from any large hardware store will protect extremely well
- easy to cut to size
- The red Tuck Tape sticks to it very well and is strong
- even if the box gets damaged the polystyrene will most likely prevent damage to the speaker

I use the 1/2" but the 1" will provide that extra protection.

Regards - Steve