THE 5th International Audio and Visual Show will hold a series of seminars presented by senior managers from various companies. These hour-long talks will be held twice daily, at 2.30 pm and 4.30 pm. There is no charge. Both the opening day seminars will concern Akai's new ''intelligent'' headquarters building, and will be presented by a representative from Y. S. Tso Ltd. The sessions tomorrow will introduce audio-visual enhancing equipment from J. H. Trachsler (HK) Ltd at 2.30 pm. There will be a lecture on AKG microphone technology for amateurs from Tom Lee Music at 4.30 pm. Friday's programme features Universal Suppliers explaining lighting techniques using Photoflex and accessories, followed by a seminar from Agfa Film and Paper. Fuji Photo Products will hold a seminar on Saturday, to be followed by an introduction to laser-active technology by the Shinwa Engineering Co.