Acoustic Research and the
Acoustic Suspension Loudspeaker

By Andrew Hayden

Web Edition

High-fidelity is a primary interest for Andrew Hayden who has written articles about Henry Kloss and KLH in previous issues of A.R.C. (June 2005 and March 2006). In this article, he describes the development of air-suspension speaker systems that resulted in smaller cabinets and improved reproduction. (Editor)

In the years following World War II, many advances were made in the sound quality of audio components, and, by the early 1950s, consumers were fast becoming interested in hi-fi setups. Full stereo sound was about to become the standard for listening to music, and the loudspeaker was a large part of the investment in a system.

Figure 1. The Model AR-1W contained a woofer only and was designed to be used with a separate high frequency "tweeter" speaker.

The choice when buying a high quality speaker that covered the entire audio frequency range was limited to stove-sized cabinets with large drivers. Many of these could put out concert-level volumes, but a major deficiency was that the lower frequencies had noticeable distortion, and their size made them difficult to incorporate into the family living room. Thanks to a New York University professor and a dedicated student, a revolution was about to take place in the world of speakers.

Villchur and Kloss

An electronics-oriented man by the name of Edgar Villchur had a radio shop in New York's Greenwich Village after World War II. He built audio systems for customers, as well as did repairs. After moving to Woodstock, New York, in 1952, he focused on technical writing and took courses in mathematics and engineering. In addition, he taught a course at New York University called "Reproduction of Sound." In his class, he discussed a speaker system he had developed in which the speaker had a very compliant suspension and relied on a cushion of air in a sealed cabinet instead of the standard mechanical spring suspension used in a nonsealed cabinet.

Villchur's woofer had a cone travel of up to 1.4 inches, achieving phenomenally low frequency response. He had attempted to sell this technology to several speaker manufacturers, including the highly regarded Bozak Company. No one was interested; most said, it simply wouldn't work.

Figure 2. A Model AR-2ax in a mahogany cabinet, ca. 1965.

One of his NYU students, Henry Kloss, became very interested. Kloss, at this time, in addition to taking Villchur's class, was also attending MIT and manufacturing the Baruch-Lang loudspeaker at his loft in Cambridge, Mass., selling them by mail order. The meeting of these two audio pioneers was the catalyst that led to a major change in sound reproduction -- the acoustic suspension loudspeaker.

AR Speakers

In early 1954, Villchur drove Kloss to his Woodstock home to show him his system, and in effect, the two agreed that night to produce this new speaker. They became partners in a company called Acoustic Research based in Cambridge, Mass.

Figure 3. The highly compliant suspension of the speaker is visible in this photograph.

The Model AR-1 was unveiled at the September, 1954, New York Audio Fair. It consisted of a 12-inch woofer designed and built by AR. High frequencies were handled by the 755A, an 8-inch full range driver of Western Electric design, produced by Altec. Both units were in a sealed ³/4-inch thick plywood cabinet filled with fiberglass. The size was just under two cubic feet with dimensions of 25" x 14" x 11", noticeably smaller than other high performance loudspeakers. It weighed in at about 50 lbs.

A Model AR-1W (a woofer only speaker), shown in Figure 1, was also produced and was intended to be used with a separate high frequency unit such as the Janszen Model 130 electrostatic tweeter. Most impressive was the fact that the Models AR-1 and AR-1W could reproduce frequencies down to 32 cycles per second with very low distortion, something the large mechanical suspension speakers could not do.

Among the features of AR woofers built through the late 1960s were a cast aluminum speaker frame, an Alnico magnet, and a treated cloth cone surround for a free suspension. Kloss was put in charge of the AR factory and is credited with 75 percent of the Model AR-1's production design. Julian Hirsch, who at the time published the Audio League Report, wrote, "The AR-1 & AR-1W have established a new industry standard for low distortion bass."

Figure 4. The rear view of the woofer from an AR-2ax speaker system.

U.S. Patent number 2,775,309 was issued in 1956 for AR's acoustic suspension design, not to be confused with the Patent Number 3,033,045, issued in 1962, which is seen on the back of many AR cabinets. That number deals with the voice coil and diaphragm support for the soft-dome, hemispherical tweeter, another industry first. This tweeter first appeared on the Model 3 in 1958.

Over the next ten years, the model lineup was expanded to include Models AR-2, AR-2a, AR-2x, AR-2ax, AR-3, AR-3a, AR-4, and AR-4x. A view of the Model AR-2ax is shown in Figure 2. The letter suffix indicated changes in the tweeter and mid-range drivers used.

Speaker components appear in Figures 3, 4, and 5. On the back of each speaker cabinet are level controls to make adjustments on the midrange speaker and tweeter, as shown in Figure 6.

If a home had a lot of fabric, such as wall-to-wall carpeting or drapes which absorb higher frequencies, an adjustment could be made to increase the higher frequency output. These controls allow the owner to fine tune the sound to the environment in which the speakers are placed, since every room has different acoustics.

Cabinet choices included birch, unfinished pine, mahogany, walnut, cherry and teak wood veneers, making these speakers look as good as they sounded! They were priced individually, but most often sold in pairs.

More AR History

Two other key players in the company's history were Tony Hofmann, a solid-state physicist, and Malcolm Low. Kloss, Low and Hofmann left AR in 1957 and formed KLH. They had great success with their line of speakers and audio components. The audio press raved about the performance of all AR speakers, which led the company to an astonishing 32 percent of the speaker market by 1966, followed by KLH in second place at 12 percent.

No other speaker manufacturer before or since, has acquired this large a market share. Acoustic Research had developed a reputation for having speakers which sounded better then anything else offered by other makers, at any price! An impressive list of spokespeople endorsed AR products -- conductor Herbert von Karajan, Louis Armstrong and Judy Collins, to name a few. The company also held "live vs. recorded" demonstrations, defying listeners to tell the difference!

Figure 5. A view of the dome-shaped 3/4" tweeter used in the AR-2ax.

Edgar Villchur sold AR to Teledyne in 1967, and this company continued producing most of the early models though 1974 when a major redesign of all speakers took place. Villchur went on to establish the Foundation for Hearing Aid Research, as well as to become a visiting scientist at MIT. As of this writing, he is still living and working in Woodstock, New York.

After leaving AR, Henry Kloss spent the next 45 years developing many groundbreaking audio products through his various companies. He passed away in 2002.

Collector Interest

As indicated by my earlier A.R.C. articles, my primary interest is in Kloss's KLH products, but clearly AR was the foundation of a major change in the type of speaker systems that interested the public. By the 1970s, millions of hi-fi speakers made by dozens of companies were in homes across America.

Today, it's the AR-1 that collectors search high and low for, often spending up to $1,000 when one is located. Many are bought up by collectors in China and Japan who love early hi-fi from the U.S. The AR-3 and AR-3a were the flagship models and can be found for $200-$500 a pair. A Model AR-3 is on display at the Smithsonian Information Age Exhibit in Washington DC. The AR-4 and AR-4x were the economy models, having an 8-inch woofer and selling for about $75 a pair.

Figure 6. A rear view of a Model AR-2ax shows the speaker connections and the mid- and high-level controls used to adjust the speaker's frequency response to compensate for room acoustics and the listener's preference.

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About Acoustic Suspension
From A 1969 AR Product Brochure

Applied physics, using air as a spring.

The air in an enclosed space makes an almost perfect spring... In AR speaker systems, the suspension of the cone from the frame is made extremely loose; then the loudspeaker is mounted in a small, tightly sealed cabinet. The air in the cabinet, resting like a spring against the cone, makes a precise and nearly distortionless suspension. This design was originated by Acoustic Research in 1954 and named "acoustic suspension."

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I think AR-2ax is the collector's bargain -- a 10-inch woofer, a midrange, and a dome tweeter, which today go for $75 to $150 a pair. These are internet prices, and as we all know, if one goes to a yard sale or church fair, you can strike speaker gold and find something for $10. This is how I spend my Saturday mornings!

References:

Acoustic Research product brochure, 1969.

High Fidelity Magazine, February 1966.

Lander, David. "Interview with Edgar Villchur." Stereophile Magazine, January, 2005.

Villchur, Edgar. Reproduction of Sound. New York: Dover Publications, 1965.

(Andrew Hayden, 4 Barton Court, Newburyport, MA 01950. ash2222@verizon.net)

Andrew Hayden has collected and researched vintage KLH electronics for over ten years.