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Pioneer HPM-100

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Title: Pioneer HPM-100  
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Subject: Pioneer Corporation, HPM, Bart N. Locanthi
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Pioneer HPM-100

The Pioneer HPM-100 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 1976 to 1979. 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-100.


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. It is housed in a plastic case, with the film (and grille) shaped semi-cylindrically in order to project the sound all 180 degrees around the front of the speaker. The HPM super-tweeter design has no dome, magnet, voice coils, or any moving parts at all.frequency response of this driver ranges up to 25 kHz.

At the time, most speaker drivers were manufactured using paper cones and foam surrounds. Another revolutionary feature that the HPM-100 speakers had was carbon-fiber blended tweeters, mid-ranges, and woofers; all with greased cloth surrounds. Carbon fiber, a technology which has an unparalleled strength to weight ratio exceeding titanium and is used in the construction of military aircraft, is lighter, more rigid, and does not rot away over time like paper and foam do. The weight of the carbon fiber, combined with cloth surrounds, allows the drivers to move and vibrate more easily, replicating sound much clearer. Compared to the usual cheap, stamped steel baskets most speakers incorporated at the time, the three drivers also have solid aluminum die cast frames, intended to eliminate resonance and unwanted rattling and noise. These features have contributed to the endurance, reliability, and longevity of the drivers.

The size of the mid-range driver is 4 inches in diameter as to match the directional characteristics of the entire speaker. Though it is small in diameter, it features a larger magnet with a lightweight cone and edgewise voice coil.

The voice coil, voice coil assembly, and cone in the tweeter are bonded with an acoustically compatible epoxy resin to help increase the rigidity of the entire vibrating configuration, meant to improve transient characteristics and aid in clean, low-distortion performance. The tweeter has a diameter of 1-3/4 inches.

The carbon fiber cone of the woofer is coated with a special resonance-damping compound to widen the frequency range and smooth out response. The woofer has a 12 inch diameter and a 6-1/8 inch magnet with a pure copper ring, to minimize third harmonics in the mid-range. These features are intended to eliminate noticeable distortion.

The crossover was designed so that frequencies at the driver crossover level overlap in order to prevent the separation of musical tones. It has crossover slopes of 6dB/oct. to avoid complicated crossover network design which could deteriorate phase characteristics. The crossovers have two potentiometers at the top front-right of the speakers, allowing the user to control the volume of both the tweeter and the mid-range drivers.

The enclosure is made of extremely dense particle board, using ported 1-1/4 inch baffle board and 1-3/16 inch chipboard sides, back, and top/bottom. The enclosure also has fiberglass insulation stapled to the interior, allowing minimal sound pressure to be absorbed by the cabinet itself. The outside of the cabinet is finished with a thick, fine grain, furniture-grade walnut veneer and has a removable black fabric grille. The HPM-100 weighs 58 pounds, 14 ounces. This was intentional, as the weight of the cabinet contributes to a richer sound. Although it is considered to be a bookshelf speaker, it is clear that it must be a floor-standing speaker because of its immense size and weight.

Alternate versions

Display models were manufactured that have clear Plexiglas enclosures (versus the solid wood with fiberglass enclosures) in order to demonstrate the inside of the speaker to customers in retail stores. Though they look interesting, they have a thinner, lower quality sound output compared to the wooden enclosure.

Different versions of the HPM-100 were manufactured with different crossovers. The original “A” crossovers were rated at 50 watts with a peak power of 100 watts. However, later “B” and “C” models, manufactured from circa 1977 on, used a more accurate, less conservative power rating of 100 watts with a peak power of 200 watts. HPM-100s that were manufactured with the “B” and “C” crossovers also contained an accent ring around the port purely for aesthetics.

Variations of the HPM-100 were released as cheaper alternatives. The HPM-60 was a smaller speaker that scaled the woofer down from 12 inches to 10 inches. The HPM-40 has a 10 inch woofer and eliminated the mid-range driver. The HPM-40 also has a cheaper vinyl finish that mimicked veneer instead of true walnut veneer.

The HPM-150 (HPM-1500 in Europe) sat at the top of the HPM line with a $500 per speaker price tag. The crossover network, midrange and tweeter all possessed a higher power ratings, additionally the midrange and woofer baskets, as well as the tweeter frame featured a polished aluminum finish. The horn loaded high polymer omnidirectional super-tweeter was redesigned, mounted on top of the cabinet and has a wider angle of coverage. The woofer was also increased from 12 to 15.75 inches, allowing the speaker system's frequency range to reach 25Hz. The cabinet quality was the same as the HPM-100, but the HPM-150 possessed a thicker walnut veneer. The foam surrounds were made of cheaper material that rotted out over time, needing to be replaced, degrading the sound quality.

The HPM-900, along with the HPM-700, were released a few years later. 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.

The HPM-1100 had a cabinet which improved on the HPM-100, being larger with built-in stands. The HPM-1100 also had 15 inch woofer; however, the cone was made of a polymer graphite material for increased rigidity at the expense of durability. The earlier series had carbon fiber cones. Like the HPM-150, the foam surrounds caused driver rot to become an issue, which resulted in inferior sound quality.

There were also other speakers released in the HPM series, including the HPM 30, 50, 70, 110, 200, 300, and 500. By 1981, Pioneer had discontinued the HPM series.


Enclosure: Bass-reflex bookshelf type
System: 4-speaker, 4-way system
Woofer: 12 inch (30 cm) carbon fiber blended cone type
Mid-Range: 4 inch (10 cm) cone type
Tweeter: 1-3/4 inch (4.5 cm) cone type
Super tweeter: High Polymer Molecular Film
Nominal Impedance: 8 ohms
Frequency Range: 30 to 25,000 Hz
Sensitivity: 92.5 dB/W (at 1m distance)
Maximum Input Power: 100 watts (“A” crossover) / 200 Watts (“B”,”C” crossovers)
Crossover Frequency: 300 Hz (Low-Mid), 4,000 Hz (Mid-High), 12,000 Hz (High-Superhigh)
Dimensions: 15-3/8(W) x 26-3/8(H) x 15-1/2(D) inches (390(W) x 670(H) x 393(D) millimeters)
Weight: 58 lb. 14 oz./26.7 kg

  • The HPM-100 woofer is actually an odd size, it is a 13 inch woofer as opposed to the standard 12 inch woofers commonly found in many comparable speakers. The HPM-100 woofer has an actual 12 inch diameter cone/moving mass. If one were to try to put an HPM-100 woofer in an enclosure designed specifically for a 12 inch woofer, it would not fit.

External links


Most 12 inch drivers are measured as about 12" across the basket, fit in a 10.5" hole, and may have a cone that is 10" across. The Pioneer HPM-100 woofer requires a 12" hole.


The information found within this topic lacks verifiable or concise scientific reference material. Due to the nature of public forums, they cannot be used as references. The claims herein this topic page are of unknown accuracy and must be reviewed.

1. Pioneer HPM-100, Advertisement. 1976: 1-4.

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