Vintage Ampeg B12XT xlr speaker cable to modern neutrik/speakon connection?

I have a nice Ampeg B12xt (!!!) that I'd like to check out the head using some modern cabinets. The original setup comes with a funky four pin xlr style specialty plug that connects into the side of the speaker cab. Does anyone know of an adapter that I can plug one end into that and the other into a modern neutrik / speakon style connector (or a simple 1/4" speaker jack)?

Thx.