This is how they should look like. Many eBay auctions are with replaced woofer cones, you betta stay away from them.
Very rare and expensive perspex version of HPM-900, boomy sound coursed by lack of internal dumping and low cabinet rigidity. They has been in sellers showroom in heydays. Sellers sold them away, when Pioneer stop making them. Today quite curious rarity. I’ve seen even perspex side-cheeks for receiver SX-1250 the other day.
I’m being fed up with people wanting various amounts of money for manuals which should be for free.
The Pioneer HPM-900 is a high fidelity, 4-way, 4-speaker Bass-Reflex loudspeaker system designed by Bart Locanthi and his team of ex-JBL engineers, manufactured in Japan for the Pioneer Electronic Corporation from 1980 to 1983. Many still exist in complete working order, with all original parts, due to the speaker being engineered for endurance, reliability and longevity.
Bart Locanthi became the Vice President of Engineering at JBL in 1960. It was under his tenure that the JBL 4310, 4311, and L-100 were manufactured. However, JBL was bought out and Locanthi disagreed with the new direction it was taking, causing him to leave in 1970, with a few other JBL engineers joining him. In 1975, Pioneer North America hired him as Vice President of Development. Pioneer gave Locanthi and his team a large budget to improve on the speakers they had designed a few years prior. It was then that he used his expertise and experience to design what was to become the Pioneer HPM
HPM stands for “High Polymer Molecular”, in reference to its then newly-developed high polymer molecular film supertweeter, a design that is used to convert electrical energy into sound to a degree that had previously only been theory. It is damped by elastic materials to prevent the deterioration of its best characteristics, and eliminates excessive harmonic distortion.
The HPM-900, were released along with the HPM-700. The HPM-700 was comparable to the HPM-60: a smaller HPM-900 with a 10 inch woofer. The tweeter and mid-range drivers on the HPM-900 and HPM-700 contained individual metal grills to protect the cones. These two speakers featured another new supertweeter design – one that more closely matched the 180 degree projection of the HPM-100. The woofers were constructed with graphite modulus – a stiffer composite material, and had foam surrounds. Also like the HPM-40 the cabinet was covered with vinyl instead of veneer.
Enclosure: Bass-reflex type
Speakers: 12-inch PG cone woofer, 4-inch PG cone midrange, 13/c-inch PG cone tweeter,
High polymer film super-tweeter
Frequency Range: 30 – 50,000 Hz
Sensitivity: 92.5 d8/W (1m)
Nominal input Power: 100W crossover version A / 200W crossover version B
Amplifier Power Range: 50-270W (recommended)
Dimensions: 15 3/8″ x 26 3/82 (H) x 15 1/2″ (D), weight: 51 lb. 9 oz.
Walnut grained vinyl cabinet with particleboard rear panel