The Vintage Pioneer HPM 1500 - Unique - is one of the famous vintage speakers and the pinnacle of the HPM series. The acronym initially inconsistently meant "High Polymer Mylar", later being consistently referred to as "High Polymer Molecular", especially in the US in the 1980s. This heavy 4-way bass reflex speaker was sold from 1977 to 1980 for $500. The Pioneer HPM 150 was not a typical high-end loudspeaker, but rather a milestone in loudspeaker technology due to two changes. It introduced, on the one hand, the use of new materials (carbon fiber) for the construction of speaker cones, and on the other hand, an innovative "high-frequency high-polymer film".