D&M Holdings own the following audio brands: McIntosh, Denon, Marantz, Snell Acoustics, Boston Acoustics, Escient, Denon DJ, Calrec, Allen & Heath, D&M Professional, D&M PSS.
Equity International owns B&W loudspeakers, Classe Audio, Rotel Electronics, and I-Command.
Quadrivio SGR owns Sonus Faber and Audio Research.
These are just a few that come to mind. Clearly there would be a lot of shared audio technology, if not shared parts and/or similar products under different brand names. Also, many companies probably do private label contract work to fill their excess capacity, by churning out many audio products under someone else's brand name. Not to mention, many products these days are probably all sourced from China. The source company in China may even make CD players, for example, for many different U.S. audio companies under their brand names.