Fleabay 511e's 600 pair BIN

Not super cheap but not unreasonable $299 ea 4 available

RARE Vintage Altec 511E Horn L K "Hard to Find" | eBay

http://www.hostboard.com/forums/hbmc...2013/01/22.jpg

Same seller 291b is same mag as 288G just change fram

http://www.ebay.com/itm/MATCHING-PAI...item460c17c6d9

Looks like the drivers sold with best offer. Might work for the horns too.