Check the listing for details. Yamaha Pro Audio Original Sound Information Series Tech Sheets, from 1992. Condition: Used, Made in Japan. Listed at 15.99 USD. Three of these original Yamaha sheets are in very good condition, and one (Multi-Way Loudspeakers?). These 1992 Yamaha sheets are both very helpful, and nice to have for the Yamaha collector! These are 4 original Yamaha information sheets, part of the Sound Information Series of technical information sheets for users of Yamaha Professional Audio Products.