Stewart Filmscreen recently announced several personnel changes. Don Parenta was promoted to sales director of its North America commercial division. Steve Cook joined the company as national sales/design engineer consultants and special accounts. Tristan Yates rejoined the company as Midwest regional sales manager of the commercial division, and Frank Mantz was promoted as Mid-Atlantic regional sales manager … Sleek Audio has hired David Gil as marketing director …Carl Mandelbaum, ex-Electrograph Systems, JVC Professional Products, joins Sanyo as northeast regional sales manager for presentation technologies.