VR-10 White Paper

For those seekers of the Holy Grail wishing to create the illusion of dramatic live musical performances in the home, Albert Von Schweikert presents the unlimited performance class VR-10. This is the ultimate speaker system, utilizing the finest design concept, drivers, cabinetry, crossover parts, and wire. Three years in development, literally hundreds of designs and parts were tested in our quest for the ultimate sound experience since this was a cost-no-object research project centered on psychoacoustics. This research resulted in many new developments and patents applied for, and will unquestionably be the engineering standard for all others to follow.

GENERAL DESCRIPTION

The VR-10 consists of five pieces: four 500 lb. towers and an electronic crossover. Twin subwoofer towers utilize 18" Kevlar infrasonic bass drivers capable of moving an entire room at 10Hz, while the main towers consist of three separate enclosures that stack to make up a full range system. The bottom and top enclosures house a super duty 10" Kevlar woofer, while the middle unit houses four Kevlar midranges, two ceramic inverted dome tweeters, and a ribbon supertweeter. These are configured in a line source array, with concentric frequency radiation patterning. These are the finest drivers ever created, and offer greater clarity with lower distortion than any other drivers ever built, at any price. Additionally, the use of twenty drivers results in a very large quantity of air being moved, critical to the illusion of listening to a gigantic orchestra in your room. There is never the sense of strain or compression common to all other speaker systems; indeed, the VR-10 was demonstrated in the largest ballroom at the Waldorf-Astoria at HIFI96 (the Stereophile show in June 1996) which was the size of a gymnasium, and was rated as one of the top three systems in the world, as voted by the 10,000+ attendees of the show. The VR-10 was the least expensive of these super systems, incidentally, making it one of the finest values in all high end audio!

OPERATING PRINCIPLE

The VR-10 was designed from psychoacoustic principles rather than being someone’s "brainstorm". Since recordings consist of microphone signals rather than the actual sound of the instruments themselves, Albert Von Schweikert determined that the speaker system must act as a large microphone in reverse. This concept insures that the resulting presentation will come as close as possible to duplicating the actual sonic event. Although this seems to be a simple procedure, it was virtually impossible to achieve this goal prior to the development of the VR series, since driver development and crossover design was not at the required advanced level.

Inverse Acoustic Replication, or AIR, was achieved by studying a typical recording microphone’s pickup pattern that was then engineered into the total system response as follows:

RADIATION PATTERN-- since the ear/brain hearing mechanism uses an acoustic principle of vectors to detect localization, ("where" the sound originates from), it was deemed highly important for the speaker to project sound waves in precisely the same manner. Consequently, the VR-10 is a highly focused concentric array with a point source originating from the super tweeter located at ear level. This point source radiation pattern simulates the mic capsule’s pick up pattern precisely, and is the key to the three dimensional holographic imaging of the VR-10. True Virtual Reality!

COHERENCY--since microphones do not generally employ more than one element, it was deemed necessary to achieve driver blending that would "fool" the ear into believing that all of the sound originates from one phase coherent source. Designing drivers that had the same sonic signature was also necessary, so that blending would be imperceptible. For these reasons, crossover frequency points outside the ear’s sensitive regions were chosen, and a new type of crossover circuit was designed. This circuit is called The Global Axis Integration Network, since sound waves are consequently generated by the VR-10 in large spheres rather than directional beams. These desired spherical waves do not pinpoint the location of the speakers, allowing the VR-10's to simply disappear. Conversely, highly directional speaker designs without the GAIN circuit do not replicate the type of radiation pattern evoked by actual instruments and thus sound artificial.

ACCURACY--microphones have small, light diaphragms that can respond to the sound pressure waves very quickly and accurately. Conversely, most speaker systems use diaphragms made from large, soft plastic cones such as polypropylene. These diaphragms are so large and heavy that they cannot accurately trace a fast transient waveform, and add up to 34% bending distortion to the signal since the cones are flexing. The answer is to use multiple small diaphragms made of a very light by extremely stiff substance, Kevlar in the case of the VR-10. Most competing speakers use two 6" or 7" poly cone woofers as midrange drivers, which is an engineering error of monumental proportions since their articulation is poor. The VR-10, on the other hand, uses four Kevlar midrange drivers of 4.5" diameter made by Focal of France, with a cone weight many times less than 6" poly woofers. The acceleration factor of these midrange drivers is measured at 1880 as compared to less than 600 for 7" poly woofers, which makes our mids three times faster to transient signals. Our 4.5" Kevlar drivers also are operated over the entire midrange region, from very low to very high, without crossover points in the ear’s most sensitive regions (a major faux pas of competing systems).

[Most competing systems use 6" woofers that require a tweeter to be used as an upper midrange driver, since these woofers do not have upper midrange response. These tweeters are usually brought in at around 2,000 Hz, which is directly right in the middle of the ear’s most sensitive region. This is the reason for competing system’s harshness at high volume levels and lack of transparency.]

The VR-10's mids are crossed over at 175Hz and 5,000Hz, so that woofers and tweeters do not have to be used to augment the midrange reproduction. On a direct comparison to electrostatic or ribbon midrange drivers, the VR-10's multiple Kevlar array is far faster, dynamic, and most important, more realistic! More about the driver construction later.

SUBWOOFER TOWERS

The bottom foundation is very important to the illusion of live music, and bass response extending to below 10Hz is necessary to achieve the correct reverberant hall size when reproducing live orchestral recordings, in addition to adding power to rock music, pipe organ, and upright acoustic bass. In order to achieve tremendous power at 10Hz, 18" infrasonic Kevlar drivers are used, manufactured exclusively for Von Schweikert Research by James B. Lansing Corporation. These provide far more impact and depth than multiple 12" woofers, especially those made from soft plastic cones. There is just no substitute for cubic inches in both cabinet and drivers when attempting to move large amounts of air, and our 18" driver is loaded into a slot loaded reflex-configured transmission line of almost 20 cubic feet. These towers are 74" tall, 16"wide, and 24" deep, and are constructed of cherry hardwood veneers covering 1.5" multiple density MDF panels. Interlock honeycomb bracing technology is used to eliminate cabinet wall vibrations that mar ordinary enclosure design. The four interior chambers are damped with Dacron using our proprietary technique called Gradient Density. This is a multiple packing density technique wherein the Dacron is very dense at the rear of the enclosure, gradually getting looser up to the rear of the driver in order to eliminate cavity resonance. This in turn allows a very tight tuning to be accomplished. Although the 18" woofers can respond to 10Hz, they are not "slow" in their operating range, since the magnetic system is several times more powerful than conventional designs. A very light cone is used as a substrate to be used as a former for the Kevlar laminations that give the cone rigidity necessary to eliminate cone breakup at very high G force levels at subsonic frequencies. The front wave of the woofer is loaded into the room by means of slot loading, which damps the woofer’s natural oscillation. Slot loading imparts the same pressure on the front of the cone as the rear of the cone sees from the air inside the enclosure. This technique ensures balanced operation from the large cone, ensuring very tight transient response and bass accuracy. In combination with the super duty driver, this is the best subwoofer ever designed. Although very large and heavy, this is the technology that must be used if concert levels are needed.

MAIN TOWERS

A stacking three-piece design is employed, so that the two 10" Kevlar midbass drivers by Focal of France can be isolated from the midrange/tweeter array. In addition, this allows separate enclosure tuning and bracing to be used, in order to optimize their separate frequency ranges.

The bottom and top enclosures house 10" Kevlar super duty midwoofers that operate from 50Hz to 175Hz. These enclosures are sealed units, with 100% Gradient Density stuffing to ensure the fastest transient response available. These woofers employ ribbon edge wound voice coils with huge magnets to allow transient response comparable to the four 4.5" Kevlar midrange drivers at their crossover point of 175Hz.

The triple layer Kevlar cones are lighter than polypropylene cones and have no bending modes, allowing far greater clarity on sounds such as kettle drum rolls and upright string bass. Conventional soft plastic or paper woofers with their cone flex do not separate the individual mallet strikes on kettle drum rolls, making the overall sound a "roar" instead of articulated strokes. On acoustic upright bass, polypropylene woofers dull the transient response, so that the sound cannot be distinguished from electric bass. Only Kevlar and carbon fiber cones have the clarity necessary for transparent sound quality, since their Young’s Modulus, or ratio of weight to rigidity, is up to seven times better than polypropylene or doped paper.

Cast frames are used since they are rigid and non resonant, and rubber surround edges are used instead of foam, which deteriorates over time. The voice coils, the true heart of the motor, are edge-wound flat wire ribbons, ensuring the maximum packing density of wire in the smallest space. This is necessary to permit the highest magnetic energy transfer from the magnet to the coil. In addition to the state of the art voice coil, a high energy cobalt magnet and thick steel top plate are employed, necessary for high efficiency and explosive dynamic range. The cones are made from Kevlar cloth, and two cones sandwich an inner damping layer made from foam pellets. The entire structure is soaked with resin and hot formed in a twenty-ton press. This resulting cone is the finest in the world, and has the highest definition and clarity of any type of membrane in existence, including electrostatic and ribbon technologies.

The enclosure is fabricated from multiple density fiber board impregnated with a resin, and is several layers thick. In addition, interlocked bracing accomplishes a honeycomb effect which strengthens the cabinet further. This eliminates cabinet wall flexing that sounds "boxy" in competing designs.

MIDRANGE/TREBLE ENCLOSURE

The center midrange/tweeter unit is sandwiched between the twin 10" woofer enclosures, and uses the same construction techniques as the woofer enclosures. However, since the midrange area is the most important in terms of aural sensitivity, we have gone to extreme lengths to ensure sonic transparency. The wall thickness is 3 inches, made from laminating three 1" boards with an internal damping layer of synthetic rubber between each board. This resulting sandwich has no acoustic transmission what so ever, and weighs 900 hundred pounds per cubic meter! Combined with the interlocking shelf bracing system, this enclosure has no measurable acoustic distortion and is unquestionably the finest design on the planet, at any price.

Besides the lack of cabinet crosstalk or distortion (resonance), this extreme weight provides a stable "mechanical ground" for the midrange drivers from which to operate. Since the drivers cannot resonate or move the enclosure, 100% of the signal energy is transmitted from the motor (voice coil/magnet assembly) to the lightweight cones. Even at a whisper level, signal transparency is beyond any competing speaker’s level of definition and clarity.

KEVLAR MIDRANGE DRIVERS

Since midrange frequencies are the most important to the human ear, and are the most difficult to reproduce correctly, great effort was expended in designing the midrange drivers. All types of electrostatic and ribbon drivers were evaluated, but their dynamic range compression and beaming problems excluded them from a world class design. By default, a small 4.5" Kevlar midrange made by Focal of France won the contest, having the best clarity, transparency, and dynamic range available. This driver has the fastest transient response, within its frequency range, of any driver in the world, due to the lightweight Kevlar cone and huge motor system. The ribbon edge-wound voice coil and vented magnet offer a very dynamic and efficient response, even at very low audible SPL thresholds. Conventional voice coils using round wire have wasted air space between the windings since the wire is not packed flat. This air space reduces the voice coil’s transfer efficiency since it lessens the quantity of wire in the magnetic gap. Additionally, the round wire voice coil is not as mechanically stable under high G-forces as a flat ribbon wire, which is important when distortion at high volume levels is considered. Power handling is immense due to these ribbon voice coils and allows very high volume levels to be used without distortion or damage.

The suspension was designed to allow very fast transient response without overhang, and uses a rubber edge roll without a memory effect that provides very high damping. At the voice coil, a phenolic impregnated fabric damper controls both v.c. alignment and rebound response. These two suspension parts have been engineered to allow very flat frequency response without suspension "lag" and enables sound reproduction that is close to live. The Kevlar cone is a triple layer sandwich filled with foam microspheres which damp any resonances, and is also formed by heat and resin in a twenty-ton press.

These midranges are matched in response and are used in quartets in each VR-10 midrange enclosure. All four of the mids operate at the bottom end crossover point, 175Hz, to share power handling and move the quantity of air necessary to capture a very dynamic range. However, since the line source must "shrink" when frequencies increase, to simulate a point source, only two are driven past 600Hz. The outer two mids are thus only operating from 175Hz to 600Hz, while the inner two mids flanking the tweeters operate from 175Hz to 5kHz.

Loading behind the mids is accomplished with our Gradient Density stuffing technique, and the drivers are mounted with a decoupling gasket made from an energy absorbing compound. By decoupling the drivers from the enclosure, resonances are thus further damped, ensuring the utmost in clarity and transparency. Overall, this is the finest midrange system ever constructed.

INVERTED CERAMIC DOME TWEETERS

Made by CERATEC of Germany, these are the cleanest sounding tweeters in existence due to exotic materials and superior engineering. Conventional tweeters generate low levels of distortion by means of diaphragm breakup and motor nonlinearity, both of which are solved in the Ceratec design. The ceramic dome is produced by coating an aluminum dome with a ceramic material and then dissolving the aluminum dome in a chemical bath. This results in an extremely light diaphragm with the highest Young’s Modulus we have ever measured. In addition, ceramic is non-resonant and does not suffer from break-up problems endemic to fabric or other domes. Additionally, the motor and magnetic system of this tweeter employ new methods of distortion reduction, allowing incredible resolution of delicate high frequencies without glare, brightness, or "edge."

To eliminate cavity resonance that occurs under the dome of all tweeters, Ceratec has provided a chamber behind the magnet and top plate allowing the rear wave to escape. The rear wave is then absorbed in a cavity filled with absorbent damping material. This technique results in breathtaking clarity and resolution far superior to any other tweeter design in existence.

Two of these world class units are used per channel for greater power handling and increased sensitivity. When compared with all other tweeter designs using metal or fabric, this ceramic unit is clearly the best. Realism is unsurpassed and listening fatigue is non existent, in contrast to other "super" speakers available which confuse clarity with brightness.

RIBBON SUPERTWEETER

Since human hearing does not extend beyond 20kHz, it was once thought that a speaker system could not be enhanced by extension of the treble range. However, research done in Japan several years ago suggests that clarity and definition are both improved when speakers can provide energy up to 50kHz. Why this is so is still a mystery, but we have incorporated a very powerful ribbon super tweeter to augment the response up to 50kHz and have found that indeed there is a large improvement in "air" and soundstage definition. This is true especially with instruments such as cymbals and triangles that have overtones rich in harmonic structure.

We have employed a four inch tall ribbon constructed of vapor deposited aluminum on a Mylar membrane, with a total moving mass less than any dome tweeter made. A powerful Cobalt magnetic system is used to drive the membrane and results in explosive transient response that is also silky smooth. A wave guide is employed in the front of the membrane to eliminate beaming at very high frequencies, ensuring wide dispersion necessary to achieve Global Axis Integration.

CROSSOVER DESIGN AND PARTS

As mentioned previously, the VR-10 uses a crossover design we call The Global Axis Integration Network, which allows wide dispersion both horizontally and vertically. To understand the significance of this new crossover design, it is necessary to study the problems encountered with conventional designs.

First order crossovers allow such a wide overlap between drivers that a comb and ripple distortion effect called "lobing" occurs. Vertically, this is due to the different path lengths from the drivers to the ear, resulting in phase distortion when the listening axis is higher or lower than the tweeter. Reflections from nearby boundaries such as the floor and ceiling also contribute to out-of-phase information due to time arrival differences.

The target area in which the first order crossover design is accurate is very small, forcing the listener to sit quite still without moving due to the lobing problem. In addition, the overlap between the drivers creates a "beam" of sound (instead of a correct spherical wave) due to the vertical alignment of the drivers, and this beam effect creates an "artificial" sound quality not found in live music.

The psychoacoustic phenomena called auditory cognitive conflict is the reaction that the unconscious mind has when listening to sound that has been generated artificially, without a counterpart in real life. (Please see our paper entitled The Psychoacoustics of Loudspeaker Radiation Patterns.)

For instance, when listening to a live acoustic guitar being played in a room, it is obvious to the ear/brain hearing mechanism that the sound is being generated spherically, that is, omnidirectionally. When this same sound is reproduced by speakers that have the beaming effect, the ear/brain hearing mechanism instantly realizes on a subconscious level that the sound is not real due to the abnormal radiation pattern of the speakers. The sound waves are not reacting to the room boundaries such as the floor and ceiling in the same manner as live sound does, and this is an instant clue to your subconscious mind that something is "wrong." Clearly, the speaker system must involve the listener with the same type of sound wave pattern that exists in real life if we are attempting to recreate a live performance. Spatial distortions can be easily discerned by a critical listener, so it was decided to study the sound pickup pattern of microphones to reproduce a correct sound wave pattern. Since microphone signals are encoded on a recording, it was thought that a more accurate rendition of the acoustic soundfield would be generated by a speaker which could behave as a microphone in reverse. We termed this concept Acoustic Inverse Replication, and designed the VR-10 speaker system to generate sound waves much in the same fashion that sound waves are picked up by the microphone.

Since we have found problems with conventional crossovers described above, we decided to use a steeper slope that would limit driver interaction and enhance power handling of the tweeters.

By studying the dispersion patterns of the raw drivers mounted in the enclosure, especially far off axis, we have come to the conclusion that off-axis dispersion is very important to optimize. The off-axis response loads the floor, ceiling, and side walls with pressure waves that will be heard by the listener as reverberation (except in an anechoic chamber), and this "power response" as it is termed, comprises 60-80% of the total sound field. Since only steep sloped crossovers can control off-axis response (due to elimination of the driver overlap that causes beaming) we have experimented with slopes from 12dB per octave up to 36dB per octave. Although theoretically only first order (6dB per octave) crossover designs are phase coherent, they are coherent only on a very limited target window. Once the measuring microphone is placed on an axis that is not centered on the tweeter, the "perfect" first order response degrades significantly, while fourth order responses remain stable. The reason for this is quite simple: if the driver overlap is eliminated, there will be no beaming effect created. Excessive overlap causes the holes in frequency and phase to occur in the first place, especially far off-axis in the vertical plane. For this reason, 24dB per octave slopes were chosen, which have an additional benefit of having an in-phase response, although rotated by 360 degrees. Further studies showed that the ear/brain hearing mechanism is not as sensitive to phase rotation as it is to degraded frequency response, and that 24dB per octave filters are below the hearing threshold for phase rotation in any event.

Since the drivers have high frequency roll- off due to voice coil inductance and diaphragm size, the fourth order response can be acoustically achieved with less than fourth order electrical filters. The Global Axis Integration Network uses our proprietary circuit developments which include servo control of impedance variations utilizing Zobel networks. In addition, most of the filters are placed in parallel rather than series, allowing fewer parts in the direct signal path. In this manner, signal purity is kept within the bounds of first order circuits.

As the world’s finest drivers and enclosure designs are utilized in the VR-10, we have gone to great expense to locate the finest crossover parts and wiring. Audio Magic solid core silver wire is used internally, along with Hovland and MIT capacitors. These capacitors are virtually hand made and are limited production samples. All inductors are air core to avoid saturation at very high power levels, and are spaced very far apart to avoid magnetic field interaction (a problem with conventional circuit boards which must place all parts in close proximity).

ELECTRONIC CROSSOVER

The supplied electronic crossover is custom made for this system by VTL and has provisions for deep bass equalization as well as volume level below 50Hz. There is one set of inputs, both single ended RCA and balanced, for the preamp, and two sets of outputs, both single ended RCA and balanced, for the two amplifiers. One amplifier is necessary to drive the subwoofers, while another is required to drive the main towers. The amplifier driving the main tower does not interact with the crossover other than to use a flow- through signal path, since the main towers are capable of full range operation. This also greatly increases the signal purity and transparency since no circuit is better than the best circuit.

AMPLIFIER RECOMMENDATIONS

A solid state amplifier of at least 100 watts is recommended for the subwoofers. Since the subs have an impedance of 8 ohms and a sensitivity of 94dB, very little power is necessary for high dynamic range and loud volume levels. However, headroom is of concern, and a high current amplifier is preferable to a low current design. The main towers work well with either solid state or tube amplifiers, and require 100 watts minimum as well. However, this speaker system has been used with 1250 watt tube monoblocks and can take all the power you can provide. Very high sound pressure levels similar to live concert levels requires a tremendous amount of amplifier headroom, so we would recommend not skimping on amplifier power.

WIRING

Each cabinet has its own input connection using heavy duty five way binding posts which can accept any type of connector, including bare wire, banana plugs, or recommended spade lugs. We can supply jumpers to connect each midbass enclosure with the connections on the midrange/tweeter enclosures, making only one high grade speaker cable necessary. If setting up an ultimate, cost no object system, two amplifiers can be used on each main tower, one driving the twin midbass cabinets, with another driving the midrange/tweeter enclosure. Albert Von Schweikert will consult with the owner of each VR-10 to personally recommend amplifiers and cables, and will also assist in setup and tuning of the total system to ensure customer satisfaction.

VR-10 SPECIFICATIONS

Frequency Response: 10Hz to 50Hz (subwoofer tower), 50Hz to 50,000Hz (main tower).

Impedance: 8 Ohms (subwoofer tower), 4 Ohms (main tower).

Power Handling: 100 watts per tower minimum, up to 1,000 watts per tower, maximum.

Sensitivity: 94dB @ one watt/meter.

Driver Complement: 2-18" Kevlar subwoofers, 4- 10" Kevlar midbass drivers, 8- 4.5" Kevlar midrange drivers, 4- 1" Ceramic inverted dome tweeters, and 2- 4" ribbon supertweeters.

Crossover: Global Axis Integration Network with servo- control Zobel impedance levelers.

Internal Wire: Audio Magic solid core, high purity silver with Teflon coating.

Crossover Parts: Hovland and MIT solid almuminum foil capacitors.

Electronic Crossover: Solid state design featuring Class A operation, with 20Hz bass EQ and level controls, includes both balanced and single ended inputs and outputs.

Subwoofer Tower: Transmission line using tuned reflex vent and front slot loading.

Main Tower: Sealed, three piece stacking design, with Interlocked matrix bracing.

Shipping Weight: One ton (500 lbs per tower).

Dimensions: Each tower is 74" tall, 16" wide, and 24" deep.

Minimum Room Size: 15ft x 20ft.

Warranty: 20 years.

Available Finishes: Cherry, dark red or natural light, with high gloss. Black ash, with high gloss. Natural oak, birch, or maple, with satin or high gloss clearcoat. Inquire about special order finishes.