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 some of the most talented ex-JBL engineers, manufactured in Japan for the Pioneer Electronics Corporation from 1976 to 1979. It is known for its paramount sonic performance and acoustic accuracy, which even exceeds speakers today that run for thousands of dollars. Many of these speakers still exist in complete working order, with all original parts, due to the speaker being engineered for endurance, and reliability, and longevity.

History

Bart Locanthi became the Vice President of Engineering at JBL in 1960. It was under his tenure that the JBL L-100 Century, the world’s most popular loudspeaker in its day, was manufactured. However, JBL was bought out and Locanthi disagreed with the new direction it was taking, causing him to leave in 1970. 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 JBL L-100 Century they had designed a few years prior. It was then that he used his expertise and experience to design, to the smallest detail, what was to become the Pioneer HPM-100. [http://www.aracnet.com/~bart/bnl2/aesbio.html] The name itself bears a striking resemblance to its JBL predecessor; this was no accident, as the HPM-100 was designed to be an "improved" JBL L-100 Century.

Pioneer designed the SX-950 through SX-1980 series receivers to match a set of these speakers. If matched with one these receivers, particularly the SX-1980, the HPM-100 is not only well-known for its excellent sound reproduction at low volumes, but also for its superior performance at higher volumes with almost no noticeable distortion or change in output sound quality. It was Locanthi’s vision and genius that made it possible. Many will argue that he succeeded in his efforts in developing one of the best loudspeakers of all time.

Features

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. [http://www.classicaudio.com/gallery/audio/hpm100.html] The frequency response of this driver ranges up to 25 kHz, exceeding the capacity of the human ear.

Even today, most speaker drivers are 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 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 incorporate, the three drivers also had 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 was precisely calculated at 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. It demonstrates that quality, not diameter, is more important.

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, substantially improving transient characteristics and aiding 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. Because of this, it is able to respond more truthfully to low frequency impulses. 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, and to assure the unified distribution of acoustic energy over the entire frequency range. 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 lowest being -3; 0 being the characteristic output; and +2 being the highest on the tweeter, while +3 is highest on the mid-range.

The enclosure is comprised 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 the rich sound the speaker produces. Although it is considered to be a bookshelf speaker, it is clear that it must be a floor-standing speaker with a stand, 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.

There were also two other versions with different crossovers. The original “A” crossovers accepted up to 100 watts max and were rated at 50 watts. However, later “B” and “C” models, manufactured from 1977 on, accepted 200 watts max and were rated at 100 watts. HPM-100s that were manufactured with the “B” and “C” crossovers also contained an accent ring around the air hole.

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 was intended to be an improvement upon the HPM-100. It contained the exact same mid-range and tweeter drivers as the HPM-100. The supertweeter design was modified, mounted on top of the cabinet and projecting 360 degrees instead of 180. The diameter of the woofer was increased to 15 inches, but had foam surrounds, which rotted away over time. Though surround rot is not much of an issue (as drivers can be re-foamed at a low cost), re-foamed drivers are diminished in sound quality compared to original surrounds, and it is cited as an engineering inferiority when compared to the HPM-100's greased cloth surrounds with carbon fiber cones. A difference in cabinet quality was that, like the HPM-40s, vinyl was used as a finish instead of veneer.

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 cheaper and stiffer composite material, and, like the HPM-150, had foam surrounds that rotted away over time. Also like the HPM-40 and HPM-150, the cabinet was covered with vinyl instead of veneer.

Though some believe that the HPM-150 and HPM-900 are improvements on the HPM-100, those that disagree cite the inferior engineering of the HPM-150 and HPM-900 as Pioneer's way of "cheapening" the HPM-100. [http://www.audiokarma.org/forums/archive/index.php/t-14684.html]

There were also other speakers released in the HPM series, including the HPM 30, 50, 70, 110, 200, 300, 500, 1100, and 1500. By 1981, Pioneer had discontinued the HPM series.

pecifications

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 Supertweeter: 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: 3,000 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

External links

* http://www.audioreview.com/cat/speakers/floorstanding-speakers/pioneer/PRD_120402_1594crx.aspx

References

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