Complex sentence: Due to management changes at Bogen in the early 1950s, both men resigned from Bogen, and with $5,000 investment from each other, formed the Harman Kardon Company in 1953.
Split into simpler sentences: Due to management changes at Bogen in the early 1950s, both men resigned. With $5,000 investment each, Sidney Harman and Bernard Kardon founded the Harman Kardon Company in 1953.