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VR-4 |
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Soundroom
In Switzerland it is now possible to buy speakers from the young company Von Schweikert Research, which is already very well known in the USA. This does not come as a suprise because these extraordinary speakers were developed by one of the reknowned experts of the North American loudspeaker industry. Albert Von Schweikert has a lot of experience in the development of loudspeaker systems. Raised in Heidelberg Germany, he and his father built a 10 watt Eico amplifier in 1957 and also the first loudspeaker with a 15" Jensen co-axial chassis. He studied violin and piano at the Conservatory of Heidelberg University before the whole family moved to the USA. As a young man in the 60’s his interest shifted to the electric guitar and soon after he earned his money as a member of bands like the "Soul Survivors", and performed with Sonny and Cher, and Neil Diamond. Besides his musical career he developed stage monitors, and in 1964 a PA system for the St. Petersburg Florida civic center was widely praised. Albert Von Schweikert studied engineering at the Georgia State University before changing to the California Institute of Technology studying under Dr. Richard Heyser. Heyser developed Time Delay Spectrometry, which made it possible to perform loudspeaker measurements without room response being a factor. In 1970 an audio experiments group was formed under Albert Von Schweikert and began spending time evaluating and developing electrostatic and dynamic type speakers. The group’s greatest achievement was a plasma tweeter filled with ozone, and a 4 meter long transmission line speaker with a low frequency response of 10Hz. Concurrent with the research group Albert also designed the Vortex "Screen" loudspeaker with a then revolutionary three way system with corrected phasing. Thanks to his excellent knowledge, especially in the interpretation of complex frequency crossovers, he started working at ESS Laboratories under Dr. Oskar Heil in 1982. Albert then designed his first linear phase crossover for the Heil Airmotion Transformer speakers. Later, Albert began working for KSC, the world’s second largest driver manufacturer and expanded his position as adviser. Albert headed over 100 projects for companies such as Apogee, Bose, JBL, Jensen and the film industries. As a consultant for Counterpoint, Albert designed a home theater speaker system chosen as the "Best Home Theater System" in 1995.
On His Own The goal of the design of the VR-4 was to develop a loudspeaker whose radiation characteristic is equivalent to the recording characteristic of the microphone because the sound of the microphone gets recorded and not the music itself. This really counts only for non-electronic instruments. The speaker acts as an acoustic inversion of the microphone to reach a new degree of naturalism and reality in the reproduction. According to Albert Von Schweikert the four criteria are: an even amplitude (off axis response and deep bass response), phase (consistency on and off axis), time (all dynamic units must create the sound in unison), as well as imaging (radiation characteristics as inversion of the microphone) must be fulfilled equally and optimized to create a natural sound character. The name VR-4 therefore stands for the creation of a virtual, but artificial reality on these four levels. The heart of this development is a highly complex frequency crossover that allows not only an even amplitude on axis, but also by means of several compensation networks, provides linearity even to someone who is out of the direct listening area. Albert Von Schweikert calls his patent-pending filter arrangement " Global Axis Integration Network". The technical short description of the VR-4 covers a two part box with a separate subwoofer containing 2- 8" bass drivers as well as a separate midrange tweeter module which is complemented by an adjustable rear firing tweeter. Because midrange and tweeter drivers were mounted in a minimum baffle surrounded by thick felt, the upper unit is covered with grille cloth mounted on a wooden frame. More details can be found in the "Technical Details and Measurements" section.
Sound Test One of the outstanding features of the VR-4 is the complete absence of any sound disturbances in the midrange. The voice reproduction, the most important criteria to judge cleanliness and a realistic tonal balance, is successfully done in an accurate recording fidelity that normally can only be found in electrostatics or certain ribbon systems. This comparison is usually made with reservation but is justified in this case. The crystal clear articulation of women’s voices and the stupendous soundstage of symphonic pieces usually are the best features of electrostatic, full scale systems. There is no bright or gritty monitor sound, instead, the VR-4 has a pleasant and charming sound character. This makes it clear that this is a very cultivated loudspeaker whose inventor not only knows the technique but also includes his experience in the concert halls. There are different methods to judge a speaker: you can listen to a short sample to learn about some of its virtues or you can let the speaker work on you for hours until you find out what you don’t like about the reproduction. The last one may be judged as somewhat negative, but is still my favorite method because it comes closer to the real domestic surrounding. With some speakers, the reproduction starts getting on my nerves after an hour or two and the walk to the coffee machine is the better choice. Some people say that this happens because I forgot the exorcist again and that I generally listen without a power filter, (although the washing machine starts it’s turbo spinning in the cellar or why that awfully expensive, steel mantled digital cable wasn’t hooked up, or, ........). Luckily, the VR-4 relieves me of the wandering through the maze of accessories. Let the well known and reliable electronics, warmed up for a short while, then check two, three speaker cables, and get ready for an incredible listening experience! The VR-4 sounds excellent even without expensive high-end components. With the VR-4 speaker, I always found myself devoted to the music and forgetting the analytical inspection for which I get paid. Ry Cooder, V. M. Baght and their two background musicians take their seats right now (A meeting by the river, Water Lily Acoustics CS-29CD). The CD insert shows a picture of the musicians during a recording session. This is a true vision which the VR-4 reflects without effort in exact dimensions. Everything is right, the horizontal distance of the string instruments as well as both percussionists further into the background. The accuracy of the attack and the systems ability of definition is impressive. The instruments are clearly defined. The focus is excellent and you can effortlessly follow the complex passages. The VR-4 develops a high degree of resolution and a very open image that reminds me of the Quad ESL-63, even though the dynamic capability clearly exceeds the English electrostatics. The bass goes extremely deep and conquers even the lowest register and that is pretty astonishing considering the small woofer enclosure (Brahms Requiem, Tel Arc CD 80092). Looking at it subjectively, the bass goes even deeper than the Wilson System Five, but doesn’t come up to its attack and aggressiveness. Also the maximum dynamics of the VR-4, which is especially important to HDCD recordings, was a very close match to our reference system. Relating to the resolution, fine dynamic characteristics and harmonic sound balance in the midrange and treble, the three times less expensive Von Schweikert VR-4 compares favorably to our reference system.
Big Soundstage
Technical Details and Measurements The midrange and tweeter are set up according to the Harry F. Olson "Gradient principle" (JAES Vol. 21) demonstrated in 1972 in the Journal of the Audio Engineering Society. This arrangement has more linear output than the conventional mounting of a midrange driver. The rear energy of the midrange driver is absorbed by a labyrinth using gradient density stuffing. The offset mounting of the midrange and tweeter serves for a time-identical soundwave launch of both drivers simultaneously. When the tweeter and midrange are mounted on a common surface as it is with 90% of all speakers (unlike the VR-4), the tweeters’ output is in advance of the midrange output and causes audible distortion. A rear mounted 2.5cm midrange treble speaker reproduces ambient upper frequencies above 1kHz to provide a three-dimensional soundstage. You find the same type of design principle in the Genesis 5 or the Wilson Grand Slamm. This arrangement causes slight anomalies off axis, however, parallel correction networks in the crossover compensate for this. The crossover is extremely complex and costly. The radiation pattern produced by this crossover is shown in the polar axis plot (which shows the speakers output in a 360 degree field). Thanks to a specialized computer program, Albert Von Schweikert was able to reduce the original parts count of 36 components down to 14, with just one part in series to the drivers. Furthermore, a 2cm thick felt pad surrounding the midrange and tweeter prevents unwanted reflections at the enclosures’ edge and sidewalls. The subwoofer uses two expensive and heavy-duty 8" units produced by Gefco in Illinois to Von Schweikert’s specifications. The surface of the driver is coated with epoxy to prevent cone deformation during loud bass output. The subwoofer enclosure is split into two vented chambers. The upper woofer crosses over at 150 Hz while the lower woofer crosses over at 60 Hz. to avoid a fat sound mid-bass. Some may ask how it is possible to develop real deep bass out of such a small cabinet. Albert Von Schweikert uses a hybrid system of passive equalization and gradient density dampening inside the box. The bass system was developed over many years and combines transmission line with aperiodic venting. The VR-4’s impedance curve was designed to be linear down to 20 Hz to eliminate impedance bumps that consume amplifier power.
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By: Daniel Schmidt |
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