Pioneer HPM-150 Restoration - Disassembly

Part 1 of restoration:
Chapter 1 - Introduction of restoration
Chapter 2 - Disassembly and getting ready for cabinet restoration

high gloss finish of walnut veneer
re-sprayed black front and top
re-sprayed brown rear
set of extra castor wheels
clean Super Tweeter
new crossovers with all new parts attached in cabinet
new internal wiring
new high quality banana binding posts
extra damping material

Pioneer HPM-150 Restoration – Part 1: Disassembly - http://audiotweak.net/2015/03/07/pion...
Pioneer HPM-150 Restoration – Part 2: Crossover - http://audiotweak.net/2015/08/08/pion...
Pioneer HPM-150 after full restoration and upgrade - http://audiotweak.net/2015/04/20/pion...

Pre- Star-Wars-ish looks for a surpising loudspeaker topped with an HPM (High-Polymer-Mylar film) super-tweeter for a 270° dispersion of the frequencies above 8,5Khz

The HPM-150 was designed by Bart Locanthi, formerly of JBL.
A suprising move from a brand which made its reputation on loudspeakers but it proved a wise one.
For from the HPM series evolved a new Pioneer division, still active and successful today : TAD (Technical Audio Devices), a specifically pro-oriented sub-brand chosen by most serious studios for monitoring needs.

Bass driver
40cm housed in aluminium diecast basket, wooden pulp & carbon fibers cone, long throw voice coil.

Mid driver
Rather small in size not to "upset the precisely calculated directionality characteristics", powered by a large magnet, edgewise voicecoil winding, "newly developed" light & rigid cone material, diecast aluminium frame and a "special design to assure substantially improved acoustic power handling, sufficient sound pressure and wide dynamic margin".

High driver
an acoustically compatible epoxy resin bonds the coil and cone to help increase rigidity ; aluminium diecast frame.

Super-high driver
Horn-loaded High-Polymer omnidirectional super-tweeter ; 3" cylindrical diaphragm loaded on a "five vertical-sectoral horns so that efficiency is improved by as much as 6dB in horizontal plane without loss of vertical directivity".

Enclosure
3cm chipboard baffle (top, front, bottom), 2cm chipboard sides and top for "optimum acoustical properties".
Computer-assisted resonance analysis and "hard-headed practical experience" for the design of the bass-reflex port.
The top of the HPM-150 is made of four wooden poles which support an unbreakable smoked glass and acoustically transparent cloth.

Despite its somewhat "dated" looks, the HPM-150 is one of the milestones in dynamic loudspeakers, the kind one always comes back to - like a Technics SB-7000.

The HPM-150 (and the HPM series at large) is however part of those which made far more mousse outside Japan like an RT-707 or SX-1250 and remaining available in the US or Germany beyond 1980.

Music: Perspectives by Kevin MacLeod

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