As H.D. Harwood’s illustrious career at the BBC Research Unit drew to a close, he discovered a new type of thin-film plastic that seemed suitable for speaker cones. With the BBC’s consent, he was granted a patent, and after his formal retirement, Harbeth was founded, and Harwood began his career as a speaker manufacturer. Advertisements in high-fidelity media announced the launch of his first product in 1977, the HL Monitor (Mk1), built around his newly patented world’s first polypropylene cone mid-bass speaker. Compared to the best hand-doped first-generation Bextrene plastic cones in early BBC monitors, it produced a louder sound, handled more power, was more sensitive, had tighter bass, and less coloration.