<font color='#000000'>Be sure to add quality of components to your report as that is also a major factor in sound reproduction.
You'll want to focus on manufacturers specifically and their processes for assembly - they will all vary, and they will all place differing importance on various aspects of their manufacturing process, I'm sure. Perhaps contacting some of these directly will yield some insight into the different factors involved in mass-manufacturing these products (tools, etc).
A thorough report will actually yield a number of manufacturers who (you will find) use substandard components and materials in building their products - and of course, a number of which excel at using great quality materials.
Sounds like a great opportunity/topic for a report - good luck!</font>