Yamaha Professional Series S5115HT speakers

Anyone have any info or experience with Yamaha S5115HT speakers? A local fellow has some for sale, and I have not found much information about them. They appear to be late 70's to early 80's vintage, and perhaps originally marketed for PA systems. They are very large. I ascertained that they work, and in my brief listen they sounded pretty good. I would appreciate any information or insight. Thanks!