June 1998

Von Schweikert Research VR-4 Generation II Loudspeakers: Sneak Peek

by Greg Weaver

The first time I heard the original Von Schweikert Research VR-4 speakers, I knew I was in the presence of something special. They exhibited such musical ease, such detail and nuance, such involvement. And when hitched to the right gear, the VR-4s offered transparency, tonality and imaging that rivaled, perhaps even bettered, that offered by the best electrostatics. After that first experienced with the VR-4s (believe me, one doesn’t just hear them, one experiences them), I wanted to learn a bit more about the man behind the VR-4s and discover how the speakers came to be. It turned out to be an interesting tale.

Roots

The first thing that came to mind about the name Albert Von Schweikert was the association of his name with the well-received Vortex Kevlar Reference Series Screens, a speaker that had achieved near cult status in the late ‘80s and early ‘90s. I started digging through my archives and came up with a couple of old reviews from 1989 and 1992. The Vortex speaker system was a three-way, time-aligned and phase-coherent dynamic system using minimum baffles and 24dB-per-octave filters, making it a first for an American company. The common opinion of the day was that the Vortex KRS Screens had spectacular imaging and that they outperformed systems by Thiel, Snell or Vandersteen in the same and even higher price ranges. Time to dig deeper.

Albert Von Schweikert has been an audio hobbyist since 1957 when he and his father built a 10W Eico amp and a 15" Jensen coaxial speaker kit, a mere two years after I entered this world. Unhappy with the sound of the speaker, Albert began to tinker with the design, and thus a career was born. As a child in Heidelberg, Germany, Albert studied both violin and piano at the Conservatory of Heidelberg University. Later switching his musical interests to the electric guitar, he went on to play professionally with The Ravens and The Soul Survivors in the ‘60s and ‘70s, and backing such groups as The Yardbirds, Sonny and Cher, and Neil Diamond. Pretty cool, eh?

While at the California Institute of Technology, Albert worked under the tutelage of Dr. Richard Heyser, who at the time was using the lab to develop a new measurement system, later called time-delay spectrometry. In 1982, Albert’s Cal Tech research led to a position at ESS laboratories with Dr. Oscar Heil, inventor of the Heil air-motion transformer (AMT). Albert designed the first linear-phase crossover network for the AMT and assisted Dr. Heil in the development of the "transar," a push-pull series of rods and discs which emitted sound from a dipolar baffle. Oh yeah, there was another young and future audio designer spending time alongside Albert and Dr. Heil about the same time: Nelson Pass, who went on to found Threshold and is now the proud papa of the Pass Labs products.

From 1987 to 1989, Albert worked as a driver designer and quality-assurance engineer with KSC Industries, the second-largest driver manufacturer in the world. During his time with KSC, he worked on more than 100 projects for companies such as Apogee, Bose, Cerwin Vega, JBL, Jensen, NHT and Paramount Pictures. It was during this time that Albert produced the Vortex Screen loudspeakers.

In 1991, Albert became a consultant to Counterpoint Electronics and the highly acclaimed Clearfield speaker line. He is also credited with designing the Concert Master Armageddon, a $59,000 ultimate state-of-the-art system. Albert founded Von Schweikert Research in 1995, bringing to fruition a dream over 20 years in the making. Impressive résumé, nes’t-ce pas?

Taking hold

Von Schweikert Research’s first speaker was the VR-4, which, by the way, won the 1997 CES Design and Engineering Showcase Award and virtually became a landmark product overnight, due in part to the flurry of controversy and conversation it sparked on the Internet newsgroups. The original VR-4 set a benchmark in deep bass response (flat to 20Hz) and also became noted for breathtaking transparency and lifelike imaging. Why would anyone want to tamper with a speaker this good?

The original VR-4 was almost as unique-looking a loudspeaker as it was sonically. To accomplish its level of imaging magic, it was engineered to recreate a dispersion pattern that would simulate the pickup pattern of an omnidirectional microphone. After all, it is the microphone’s voltage signal that is recorded, not actual music. This technology has been termed Acoustic Inverse Replication[TM]. To "decode" the original soundfield, a unique crossover was also developed, called the Global Axis Integration Network[TM].

These proprietary circuits were developed to limit lobbing effects and non-linear off-axis response and actually enable the consistent phase behavior necessary between drivers. The architecture of this circuitry somewhat resembles first- and second-order filters. This describes the basic operation of the Global Axis Integration[TM] part of the decoding. Once the proper signal for the drivers has been developed, a correctly designed speaker system must then be able to project the inverse of that mic signal in order to complete the decoding of the signal and translate it back into an accurate facsimile of the original sound field. Enter the Inverse Acoustic Replication[TM], which is achieved through carefully engineering the radiation pattern created by front and rear driver arrays to complete this process. Whether all this techno-speak is white-paper wizardry or well-meaning whitewash is immaterial. The sonic result is what counts.

The flower blossoms

The foundation of the original VR-4, both physically and musically, came in the form of a bass cabinet housing two 8" hybrid woofers which were epoxy treated for extreme stiffness. Albert chose to use two smaller woofers that offered far greater transient-response speed and articulation than one large driver. The woofers were also sealed in separate chambers and tuned to separate frequencies. The crossover used what is known as a distributed-resonance induction circuit to help eliminate a common impedance peak found in ported systems and also help to greatly increase amplifier efficiency in the critical bottom octave, helping the speaker down to its 20Hz capability. The upper woofer was crossed over at 125Hz while the lower one was crossed over at only 60Hz, helping to eliminate that midbass thickness that so often finds its way into other two-woofer designs.

The midrange/tweeter module housed the front-firing midrange and tweeter as well as the rear-firing ambiance-retrieval tweeter, giving the finished speaker an overall dimension of 13.5"W x 19.5"D x 46"H. The midrange and tweeter baffles were mounted in "free air" and covered with a cloth sock for cosmetic purposes. It was essentially a cloth-covered frame (slightly reminiscent of the Vandersteen genre) covering the staggered driver array (required to preserve the remarkable imaging and staging) which allows the VR-4s to retain a conventional appearance. This upper module docks to the bass module, seating inside a wooden frame and resting on proprietary synthetic rubber feet, helping to eliminate enclosure resonance which could mar the all-important midband.

Midrange frequencies were provided by a 5.25" carbon-fiber driver in a cast-aluminum basket recessed in a felt-covered sub-cabinet for time alignment and using a special energy-absorbing surround compound called Norsorex. This surround material was chosen because it offered several times more damping than foam or even butyl rubber. This select driver was then housed in a labyrinth with non-parallel walls to channel the energy away from the driver, gradually attenuating the back wave, in an effort to avoid the most common causes of midrange coloration. The driver had a natural response of 57Hz to 12kHz—quite remarkable. Crossed over from 125Hz to 3.5kHz, this driver was well able to handle accurately this range of frequencies with ease and greater dynamics, and this was responsible in no small part for the speakers’ unmistakably natural sound.

High-frequency information was provided by two tweeters, one front-mounted and time-aligned with respect to the midrange driver, and the other rear-mounted for ambiance retrieval. The front tweeter was fabricated out of aluminum and treated with a special rubber coating to allow for both clarity and sweetness. This primary tweeter was crossed over at the midrange’s upper limit of 3.5kHz. The rear tweeter was a 2" midrange/tweeter with an attenuator to control the volume of the output and permit matching for any combination of room size and speaker placement.

The mature plant

The case could be made that tampering with such a successful achievement would be foolish. So why do it? During the development of the VR-6, and VR-8 (and one lone pair of statement loudspeakers, the VR-10), much was learned. The VR-8 and VR-6 are now available and could be said to represent the absolute state of the art in dynamic-loudspeaker design. The one pair of VR-10s, which was built to demonstrate at the 1997 CES, was really more of an experiment than a product meant for the mainstream, and was snatched up by a Microsoft executive right after that show. But it became inevitable that the knowledge gathered in the creation of the more ambitious and considerably more expensive models should trickle down into the precedent-setting younger sibling.

In developing new technology for the VR-6 and VR-8 speakers, the Von Schweikert Research team discovered a commonly overlooked problem now called the "masking threshold." Ultimate clarity and transparency is highly dependent on low-level detail. However, this detail is normally "masked" by effects such as crossover-part dissipation, subtle cabinet vibration, and driver non-linearity. Each isolated problem is not severe, but the sum total of these effects destroys realism. The removal of these problems provides greatly enhanced transparency, linearity of frequency and phase response, dynamic range, and image focus.

As its Gen. II designation implies, the new design was more of a modification than a radical departure from the original. The first improvement to the original VR-4 was the inclusion of custom-designed low-loss capacitors and inductors, along with custom-engineered solid-core five-nines copper wire with a foamed-Teflon dielectric. All parts and finished boards are measured with a computerized test station for adherence to the original prototype. Critical inductors, whose fields were interfering with other parts of the crossovers, were moved further away from those affected components. An aluminum tweeter matching the front driver is now used for the rear ambience to ensure proper coherence and clarity, also resulting in more realistic depth of field. There is a new tweeter baffle to ensure linear frequency and phase response off-axis. The tweeter baffle was also rounded (using side flaps) to allow airflow integration with the midrange. The claimed payoff? Much finer low-level detail and clarity is now audible along with increased efficiency and dynamic range.

There is a new midrange enclosure as well, and the original transmission-line tunnel has been re-engineered to allow better airflow both internally and externally, resulting in greater clarity through the better elimination of internal standing waves. This was partly accomplished by rounding the front baffle, which allows a more linear frequency response off-axis due to a linear airflow.

Deep-bass response is rumored to be tighter and faster due to a new Theile/Small vent alignment, utilizing damped internal airflow and larger flares. Wind noise, turbulence and overhang have been all but eliminated, resulting in greater clarity and definition. The woofers have laminated cones of fiberglass resin and polypropylene, and are extremely rigid yet light in weight. The woofers are loaded into a modified reflex enclosure with aperiodic damping similar to transmission-line loading, generating very powerful bass that is also claimed to be very fast and tight. The separate woofer enclosures are 100% stuffed with a special gradient-density packing, greatly reducing cavity resonance and "boom." Tuning and pressure release are accomplished with very large flared ducts (5" diameter) with felt linings to reduce wind noise and turbulence.

To visually integrate the VR-4 Gen. II into smaller rooms, the speaker has been downsized, with the width of the cabinets reduced substantially. Also in an attempt to eliminate the blocky appearance, the rear of the midrange/tweeter module has be angled. The new appearance is visually noteworthy, and the smaller footprint is very apparent when compared to that of the original units.

Neither Von Schweikert Research nor the new VR-4 Generation IIs are overnight success stories, although they may seem to be at first glance. Next month will follow my listening experiences with the new speakers. See you then.

...Greg Weaver
gregw@soundstage.com

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