I am not expert on what manufacturing moved to China and when; I have not been involved with the company since the mid 1990s. At that time the only off-shore components were some European electronic components. My general impression is that the hi-fi music products were always assembled in Lexington, although some parts, including drivers, were made partly or wholly in China. Home theater products were made at increasing levels in China, more so after Jim's death in 2009. Testing and QC remained in Lexington throughout. These are my opinions developed from various conversations, but are subject to correction.
I know from other involvements that it has become increasingly difficult to impossible to source many sophisticated components from North America / Europe due to changing market conditions.