How do pack a pair of large speakers

You buy new packaging from the speaker manufacturer.

@kr4

+1

or moving companies have folks that construct packaging on the fly. They have wood and can package anything. You can have it done, just for a set of speakers... but it is expensive. For instance about seven or eight years ago I was going to send some speakers... it was over $500 to fabricate crates... and they were not large. So shipping them... was over $1,000 (crate plus fright). They were probably only 40 lbs each.

I made a couple runs at it and gave up.

Even if you can purchase the box and packing material, the cost will be quite high because it has to be shipped to you and most of the fost of shipping is for the volume the box takes up.  It can cost many hundreds of dollars to get a set of factory boxes.  If you are friendly with a shop, they may be able to supply you with an appropriately sized box.  Speakers should be double boxed.  Also there should be enough room to squeeze in as much foam padding and/or bubble wrap.  Make sure such padding and wrap covers the entire container so that no shifting of contents will leave any part uncovered.

Do not trust a shipping store to do a good job packing your item for you.  I’ve seen horribly mangled gear that was barely protected shipped by such stores.

Good luck.

See Kr4 comments. That’s the proper way to do it. Otherwise you are screwing the buyer or just taking risks with shipping. Even professional proper shipping service and OEM packaging can still damage speakers at the hands of USPS, UPS FedEx or Freight companies. But it’s the best chance with OEM packaging.

Craters & Freighters are the best, it's their job!

https://www.cratersandfreighters.com/

Use a moving companies shipping section. I've used Day and Ross a few time to move larger heavy speakers with no issues. They come to my house, wrap them up in padding and protection put them on a pallet and take them away, delivered to the other end's door. never had an issue, actualy easier then smaller items that i have to lug to the post office/etc.  

UPS has pack and ship as an optional service at SOME, not all locations. Give them the weight and dimensions, destination, they give you an estimate.

You drop them off unpackaged, they give you a final price, a bit more, a bit less ... They are responsible for packing and delivering, and the deal is done in your name.

I have used it to buy when a seller says ’local pickup only’, even bought from Canada, had shipped here. Tricky but it all worked out. Just need to have them drop them off unpackaged at the UPS location with Pack and Ship nearest them

IF you are selling, give the weight/size info to the buyer, let them make the deal with UPS in their name, you just drop them off. You can find specs online.

Carefully.

strong outer protection (box) speakers are secured inside the box with thick surrounding ( of bubble wrap..) Themocol/sponge spacers (3-6" thick) which keeps object in place no matter what. securing Corners are very important. Plastic cover to take shower. Imagine what abuse box is going to get during transport. Handlers not aware of how fragile, sensitive or expensive is product inside. Handlers may throw from 15feet high. Box may sit exposed to all elements. Forklift may brush the carton.

I recently moved and had the moving company do "custom crates" for heavy, expensive monitors. Turns out they charged $300 bucks for it and all it was was a guy taping some cardboard he cut on the fly to the speakers. Fortunately they weren't damaged and I got my money back but definitely go with original packaging or pay service that does this and only this.

The usual 2 ways....

Badly or correctly.

Will likely cost about the same if the shipper even considers the first...perhaps more on the advised insurance...

What model of speakers are they?  This would determine how large and heavy they are and if they need to be crated rather than having cardboard boxes. 

You buy new packaging from the speaker manufacturer.

This should 100% be your go-to if the company is still available for it. Barring that, TMR does their own custom injected Styrofoam, molded to the shape of the speaker/component on one side, the intended box on the other, and covered in plastic - that stuff works pretty well, but I’m not sure of its upper limit for size & weight of really big speakers.

Closed-cell foam snugly molded to the speaker ends (optionally with an extra middle piece for tall speakers) is what many manufacturers choose for a reason. Needs to be at least a few inches thick.

This should go without saying, but bubble wrap and packing peanuts and the like are useless here.

Outer box should be double / triple wall cardboard at a minimum and with corner reinforcements for larger suff.