Location, location, location. Although there are more factors that go into a successful audio/video show, unless the location and the venue are right, it's really an uphill battle. The organizers of the Toronto Audio Video Entertainment Show recognized that unless the show is in location that's convenient and has a venue that's attractive, only the most devoted audio/videophiles will attend.
They got it right by selecting the King Edward Hotel, a luxury hotel in downtown Toronto, with many restaurants nearby, and also close to theaters. All right, so parking is expensive, but the King Edward is steps from the subway, so it's easily accessible by public transit.