Hegeman Standard / EICO HFS-2
The Hegeman Standard Loudspeaker is the "smaller brother" of the Hegeman Professional. In its time, it was easily the most famous of Hegeman's speakers thanks to EICO, which licensed the design from Hegeman in 1958 as their "Standard Speaker System #HFS-2" or simply the EICO HFS-2.
EICO made a full-court press marketing it: putting the speakers in the hands of as many reviewers as would take it, and on the covers of several leading audio magazines. The highly unusual design of the speaker surely helped it make such a splash.
Hi-Fi & Music Review - Feb '58
"A whole batch of really radical ideas enter into the design of a new loudspeaker, invented by Stewart Hegeman, now manufactured by EICO as their Model HFS-2. Outwardly, there is nothing sensational in the appearance of this small speaker system, which looks like a slightly oversize hitching post and takes up only one square foot of floor space. But behind the grille lurks a strange shape. A science-fiction fan might describe it as an inverted helmet for the men from Mars with pointed heads. People with a more down-to-earth outlook may feel that it resembles a double-walled ice-cream cone..."
"STEREO'S coming of age has caused designers to focus new attention on the special factors applying to that type of reproduction. Chief among these factors, which are largely responsible for the "spread" and naturalness of stereo... are omnidirectionality -- not merely "fanning out" of the sound but true circular distribution and linearity of phase shift (constant time delay) in the acoustic transmission system represented by the speaker. Thus the speaker system on our cover this month, the Eico HFS-2, designed by A. Stewart Hegeman, takes into account not only the traditional demands of speaker systems, but also the special requirements of the new art of stereo..."
Audio - April '60
"COVER PHOTO- Attractive installation in typical New York apartment. Designed by Stewart Hegeman, this installation features a Harman Kardon Madrigal ST -360 AM /FM tuner, Citation I stereo preamp, Citation II power amplifier, two EICO HFS -2 loudspeakers (designed by Hegeman), Rek-O-Kut turntable, Dyna-B&O professional aria and cartridge. Turntable cover is clear plexiglass, and is removed and stood on end when turntable is being loaded. During playing - or any time - the cover is a fine protection against kiddies or cats - the one at upper left is part Siamese, and is for real. "
"This speaker has aroused considerable interest, discussion, and disagreement among HIGH FIDELITY s staff members. Some who have heard it think it possibly the most musical and most realistic -sounding thing in its size or cost range. Some are less enthusiastic about it, conceding its smoothness and freedom from distortion, but maintaining that its sound is short of impact, even muted...
My conclusion about the EICO is that, under ideal conditions, it can sound most impressively realistic, and is describable as an eminently musical reproducer..."
The Design
Norman Eisenberg and Stewart Hegeman wrote an exhaustive description of the Hegeman Standard/HFS-2's final design here, in the September 1958 edition of Radio Electronics. I recommend you read it before proceeding. All I'll say is:
The design of the Hegeman Standard / HFS-2 is best described as a budget version of the Hegeman Professional.
Like the Hegeman Pro, the Hegeman Standard featured Hegeman's Lily Tweeter to furnish frequencies above 8kHz and a split slot-loaded conical horn to furnish frequencies blow 200Hz. But whereas the Hegeman Pro used a pair of woofers for the bass and another pair for the mids, the Hegeman Standard uses only one 8-1/2 inch woofer per speaker to furnish all bass and mid frequencies.
In this case, the woofer is a modified Philips/Norelco 9750M full-range driver. Its rear loads a small version (half the Pro's length) of the Hegeman Split Slot-Loaded conical horn. Its front, which was modified with Hegeman's trademark boat-shaped whizzer cone and diffuser/phase plug, played into free-air facing the ceiling. The tweeter was mounted co-axially above it. Thus acheiving a hemispherical, phase coherent response.
While these features were present in all versions of the Hegeman Standard / EICO HFS-2, they were revised twice in its lifetime.
The Three Lives of the Hegeman Standard Loudspeaker
The Hegeman Standard's design was revised twice in its lifetime, resulting in three distinct versions of the same speaker. The earliest version was marketed directly by Hegeman under his "Hegeman Laboratories" brand and was known as the "Hegeman Standard Loudspeaker". The second revision came alive as the EICO HFS-2 speaker. The same was revised again for EICO, and became the third and final version. I will start with the final version, and work my way back.
EICO HFS-2 (Hegeman Standard v3.0)
This final and third version of the Hegeman Standard is the version described in the article linked at the top of this page.
The Tweeter
The V3 tweeter was identical to the tweeter in the Hegeman Pro. The magnet assembly was custom manufactured by Best Speaker Co. (EIA code 371) to Hegeman's specifications.
The cone was a laminate of aluminum foil (yes, standard weight aluminum foil like you have at home) and a single sheet of tissue paper bonded together with alkyd resin and pressed until it was dry. The use of alkyd resin was verified by FTIR and EDS analyses (it pays to know some university professors). I have measured at least 6 of the cones. They each weigh exactly the same: 1.1 grams. From tip-to-bottom are exactly 4-3/8 inches tall.
The phase plug is made of the same materials but used many layers of tissue paper instead of one to create a very stiff material.
The tweeter has a resonant frequency of about 150Hz.
The Woofer
Hegeman used a Philips/Norelco 9750M full range driver as the base for the Hegeman Standard's woofer. It's a powerful speaker with a nearly 3lb magnet (1.3kg) that provides 1.3 tesla in the magnetic gap.
The main cone assembly (cone, spider, coil) weighs in at just 5.7 grams. For V3, Hegeman affixed to it a 3.7g boat shaped whizzer cone made of a similar laminate as the tweeter's cone (aluminum foil, four sheets of tissue paper, bonded with alkyd resin). From tip to tip is measures 6.5 inches.
Attached to the center pole piece of the woofer is a boat-shaped phase plug/diffuser. It is made of the same laminate as the tweeter's phase plug.
The edge of the cone was treated with some sort of stiffening substance raising the woofer's resonance to about 90Hz. It may be counterintuitive, but raising the resonance actually benefits the bass response in Hegeman's bass enclosure.
The Bass Horn
The rear of the driver plays into a 3.5L chamber stuffed with Kimsul insulation. This chamber is damped by two 1.5L Helmholtz resonators on either side of it that are tuned to eliminate unwanted resonances that would otherwise create a deep 110Hz void in the horn's response.
The horn's throat is 46sq cm. The split begins immediately and is accomplished by way of a tapered center divider. Each half of the horn follows a conical expansion over a length of 174 cm, reaching a cross-sectional area of 250 sq cm (a combined area of 500 sq cm).
In a normal horn, the ends would be open. But in this design, Hegeman terminated the horn using two slots: a pair of 1.0 x 1.5 inch slots on the right side, and a pair of 3.5 x 0.43 inch slots on the left side. According to Hegeman, the slots' asymmetrical sizes and placements helped achieve a smoother frequency and phase response from the horn.
The entire horn is made of 1/2-inch plywood.
The Early EICO HFS-2 (Hegeman Standard v2.0)
V2 of the Hegeman Standard (the first version of the EICO HFS-2) is markedly different from V3.
The woofer's whizzer cone and diffuser/phase plug are of different sizes and materials.
The tweeter's cone and phase plug are of different sizes and materials.
The crossover is set at 6kHz and consists of a 2nd order high-pass for the tweeter, and a 2nd order low pass for the woofer.
Also interesting to note (I regret not photographing it when I owner a pair of this version) is that Hegeman blocked four of the 6 circular openings in the woofer's basket, leaving open only the two that aligned with the opening of the horn's throat (this can be seen in the cutaway photo). This presumably increased pressure on the back of the cone during excursion. To what extent this worked and to what end it was done, are unclear to me.
I unfortunately cannot locate my own photos or the notes I made of the inside of V2. The two photos showing the inside of the speaker are borrowed images, but they show well the differences described above:
Note the woofer's whizzer is much smaller (about 3.75 inches across) and made of a stiff, black construction paper instead of the aluminum/paper laminate of V3.
Note the black conical black-painted steel diffuser instead of the aluminum/paper laminate of V3. It attaches to the legs of the tweeter's mount and reaches down to the woofer's dust cap, which, in this speaker, was a 1-inch round piece of flat felt.
And then, of course, there's the tweeter. The magnet structure is identical, as is the spider. But the cones and phase plugs are very different.
The V2 tweeter cone was 6.75in tall, about 3in in diameter (mid opening) and weighed 1.7g. Its increased size and weight resulted in a tweeter with a resonance of about 100Hz.
The cone was constructed of a single sheet of bond paper varnished in alkyd resin. Visible here is the watermark of the paper's manufacturer.
Here's a closeup of the tweeter's phase plug/diffuser. It is made of a stiff, long fiber construction paper. The same material was used to make the woofer's whizzer cone.
Hegeman Standard v1.0
These photos represent the only example of a Hegeman Branded "Hegeman Standard Loudspeaker" I have come across. They come courtesy of an audio enthusiast named Gary who emailed them to me years ago.
Despite looking quite crude, the Serial Number (No. 221) indicates this was not a prototype, but a production version of the speaker.
While the basics of this speaker are almost identical to V2, there eare some large differences.
Each half of the split slot-loaded horn terminates in one large slot instead of pairs. And the total area of each slot is larger than the combined area of the pairs on V2 and V3. Simulations indicate the larger slots would have resulted in a horn with greater efficiency in the 100-200Hz range compared to V2 and V3.
The Lily Tweeter's cone is still made of varnished paper and appears to be the same size, but did it not have a hemmed edge. The hemmed edge was said to help suppress unwanted resonances.
The woofer's whizzer cone was also made of varnished bond paper instead of the construction apper in V2.
The woofer's phase plug/diffuser is much smaller and boat shaped (like in V3). It appears to be made of a sheet of Hegeman Laboratories letterhead.
Though the source of these images was not able to provide values for the crossover components shown here, the configuration appears the same as V3.
The woofer has no crossover, only a tone control circuit composed of the larger inductor on the right and the potentiometer it is attached to. The tweeter's crossover is 2nd order, comprising of the capacitor and smaller inductor on the left. Whether the crossover frequency was 6kHz (like in V2), 8kHz (like in V3) or something else, I do not know.