Super Tower III / Special Ribbon Edition

Audiophiles visiting us from other planets must think the earthly High End has gone mad. Recent Hifi shows across the country have exhibited dozens of systems priced in six figures, with several in the six hundred thousand dollar range for equipment only. A million dollar installation plays in a New Jersey home; there appears to be no upper limit on what consumers are expected to pay. Lofty prices, however, have not been joined by an appropriate jump in reproduction quality. The arrogance and cynicism of the industry is neatly capsuled by the following true story: a journalist for a leading "buff book", aware of the cost-to-retail ratio of speaker systems, queried one manufacturer why his repackaging of five hundred dollars worth of cone dynamic drivers sold for $70,000 the pair. Came the succinct reply: "You must understand, in the High End, you pay for the price." 

This poses another question: just what would represent the state of the art in loudspeaker design and performance, and how much would that cost, if audiophilia is not to be considered merely an affliction of the rich and gullible? In our opinion, there is but one answer: a widerange, transformerless, push-pull ribbon, coupled to the best dynamic bass section science can devise. There are many reasons for this statement, and they are worth a closer look. 

In this past decade there has been much progress in materials and design of speakers of all kinds, including cones and domes. Even horn systems, once consigned to salt mines of Public Address, have reemerged in tandem with low-power Single Ended Triode amplifiers. What has not improved are the laws of Newtonian physics: all mass has inertia, an unwillingness to change from rest into motion, or motion back to rest. Accordingly, the overriding imperative of speaker design has to be reduction of moving mass. No dynamic driver with a voicecoil, bobbin, and diaphragm attached can be slimmed down sufficiently to react instantaneously to an incoming musical waveform. This applies to today's lightest, stiffest cones, smallest domes, and planar magnetics both single-ended or push-pull. 

Only two drive systems offer truly low moving mass: the electrostat and the ribbon, with the ribbon enjoying the advantage by far. "Stats" need a thick, noisy plastic diaphragm, doped with a conductive slurry, a very high polarizing voltage which easily arcs across this barrier, an undamped suspension (usually, the edges are merely clamped down), and a large surface area, since stats are extremely inefficient. The wide, large panels are highly directional, dipolar in their radiation pattern (a big drawback at bass frequencies), and ragged in their frequency response. Set in motion by a music signal, they flex, shimmy, and twang. There is no practical solution to these problems. Low moving mass is the stat's sole virtue, but this is enough for many listeners, enamoured of the absence of "cone squawk" and typical enclosure output. 

Ribbons have been with us since the 1930's and fall into two broad categories: single- ended "leaf" type ribbons which are driven magnetically from one side only (usually the rear), relying on inherent springiness for their return motion, and the push-pull ribbon, with rows of magnets on either side. Examples of single-ended ribbons are ubiquitous: EMIT's, EMIM's, the popular trapezoidal panel ribbons, and many others. Look for the telltale slotted magnet structure behind the diaphragm. Single-ended ribbons suffer from very high distortion, typically an appalling 30% THD or more. Their distortion products ride only about 10dB or so below the signal and are extremely audible. Single-ended ribbons' success in the marketplace is attributable to their quick, responsive sound quality and the forgiving nature of the human ear. 

Push-pull ribbons can be outstanding performers, held back primarily by their extremely low impedance. Ten years ago VMPS built the Widerange Ribbon, a modular system with a six-foot midrange ribbon whose DC resistance hovered near half an Ohm. This is not a suitable load for any amplifier, including today's best. The recourse has traditionally required an impedance-matching transformer, which tends to saturate, shift phase and generate other considerable distortions of its own. 

In the Special Ribbon Edition of the VMPS Super Tower III, we use nine of our most advanced Neo ribbons for it's midrange array. Our ribbon radiates as a dipole, with no enclosure coloration; its back wave is controlled by a foam damper which prevents the comb filtering so characteristic of dipoles while retaining their airy spatiality. Vertical dispersion of such a tall ribbon is, of course, ideal; horizontal dispersion of midrange array is extremely broad and linear. Low, low moving mass of Neo reibbins approximates the mass of the air it must move, for an ideal impedance match. With output flat from 280 Hz to 6.9 kHz, it needs only mate with an equally good treble ribbon, which by good fortune also exists in the form of the SRE/ST3's free-swinging six-inch ribbon tweeter, the moving mass of which is one-onehundredth that of the finest moving-coil dome in existence. These two ribbons, midrange and treble, measure and sound so superior to anything else yet invented or imagined that the only obstacle to their use in High End speaker systems would be cost. You could purchase the entire drive complement of a highly-reviewed $65,000 megaspeaker for the price of this midrange array; a cost accountant (the real decision-maker at most companies) would note right away he could buy fifteen tweeters found in his "Class A" $90,000 system for the same money as one of our six-inch treble ribbons. Thus there emerges the real paradox of latter-day High End speakerbuilding: the best drivers are simply too expensive for use in the most outrageously expensive systems available. 

The low moving mass of ribbons in general works against them in the bass, where low system resonance dictates high mass, high compliance woofers. VMPS has a reputation established over 29 years for constructing some of the finest bass systems in the world. We exploit this experience to build the six-foot-four inch bass column of the SRE/ST3. Four 30cm (12") woven-carbon fiber, phase plugged active drivers (with Soundcoat-damped baskets) push one mass-loaded, slot-loaded woven carbon fiber passive radiator to cutoff below 16Hz at levels near 120 dB/1m SPL. Cabinetry is both massive (204kg, 450 lbs) and unique in design and construction. The primary material is a synthetic granite, backed by additional thickness of MDF (front, side, and rear baffles each having different thickness, masses and resonance frequencies). The synthetic granite exhibits damping properties lacking in the natural stone and thus transmits sound poorly. "Panel talk" is reduced 10 dB more by the internal application of Soundcoat, a borosilicate ceramic damping compound . A current trend in megaspeaker design is the more-and-more massive cabinet, one brand outdoing another to the point where the heaviest scale in around 500 kg. Increased mass does translate into increased moment of inertia: the cabinet will strongly resist its tendency to rock back-and-forth minutely in sync with woofer motion. While it would be possible to whittle a speaker cabinet out of the side of a mountain, and achieve nearly infinite mass, such an enclosure would still have considerable output (stone and cement carry sound well at high velocity) in the form of vibration and flexure. The damped composite of the SRE/ST3 is sufficiently massive, well damped, and a bad-enough sound transmitter to be as inert a cabinet as the costliest competitors no matter how much they weigh. 

Audiophiles have long debated the virtues of tube vs. solid state design, with vociferous advocates on both sides of the debate. Transistors generally can deliver much more current than tubes and be directly coupled to the speaker. Tubes are more linear than semiconductors, however, and often produce more realistic mids and trebles. For these reasons, the SRE/ST3 is supplied with a 24 dB/octave electronic crossover. Tube fans could then hook up the Single-Ended Triodes, zero or low-feedback pentodes, or Class A EL34's (our favorite) for midrange and trebles only, while Solid-Staters can enjoy the diminished intermodulation distortion of true biamp or triamp operation. The great flexibility so achieved can be a true joy to the person wanting the maximum from his system. The passive crossover to the mid and trebles is outboard and is easily removed for service or updating, obviating the need to ever ship the speaker system itself back to the factory or service technician. The FET-input active crossover for the bass range boasts premium parts and a huge, 1,000,000uF/120W power supply, by far the heftiest power supply for line-level commercial gear ever. 

The SRE/ST3 may be ordered in a number of custom configurations. Standard finish is piano white or piano black over the granite, and at least 78 wood veneers such as Brazilian rosewood, burled walnut, maple, cherry, and oak are also available. Crossovers feature the finest passive components, all trimmed to exact tolerances. Internal wiring is 8 gauge for the bass, and progressively smaller gauges of our exclusive Teflon insulated silverplate stranded cable for mid and treble. Cabinets are not spiked, but rather isolated by a Soundcoat damping sheet which prevents cabinet output from driving the floor. Floors are mostly wood or concrete and carry sound more efficiently than the air. However, spikes very effectively couple a speaker cabinet to the ground, sending its output to the listening position ahead of the airborne sound and generating a "ghost" signal which confuses the ear to the detriment of imaging and linearity. 

In the past fifteen years we have travelled extensively, visiting VMPS dealers and owners in their stores and homes, gathering data on speaker performance in nearly 200 different rooms. We have also auditioned countless systems of other manufacture in setups from mid-fi to high audiophile. The inescapable conclusion is that many setups sound dreadful and their owners, including dedicated and sincere folk, lack the experience and equipment to setup and operate their systems properly. Even manufacturers and reviewers make mistakes or neglect important aspects of speaker placement or room treatment - vital for full enjoyment of the tremendous performance this magnificent system can provide.

Audio Magazine August 1998

Mini Setup Instructions for ST III/SRE 

1. Connect the electronic crossover between preamp and bass amplifier and use crossover level controls to match bass output to mid/treble levels. It is also possible to vary the electronic crossover frequency (which is factory preset to allow for the approx. one-octave overlap required by an electrically in-phase system such as the SRE/ST3) slightly to achieve maximum clarity. All adjustments on the system (including the tweeter ribbon level control on the outboard passive crossover and the bass damping adjustment on the bottom-firing passive radiator) are intended to increase clarity and definition, extend and tighten bass, and adapt the system to the series resistance of the speaker wire and damping factor of your amplifier. When we set up the SRE/ST3, we adjust each of the controls one at a time, turning them up or down by the smallest possible increment. Muddiness, brightness or lack of deep, widespread soundstaging can all be alleviated by these adjustments, provided they are performed in the smallest possible steps!! 

2. As indicated above, it is easy to dial right by the correct control setting for the treble output, bass level, or crossover frequency. Electronic crossovers are now equipped with ten turn pots which permit a 1.8dB adjustment plus-or-minus for each full turn (360 degrees) of the volume control. 

3. Connect the bass amplifier speaker wire to the large gold binding posts on the back of the main woofer column. Stand the passive crossover enclosure behind the bass column and plug the five pin connector into the five pin socket located on the back of the bass column near the bass input binding posts. If you so desire you can elevate the crossover box with spikes or Tiptoes, since the wiring with the five-pin plug is intentionally very short. Set the treble level control initially at about 11 o'clock, then make level adjustments upward in the smallest possible increment. Listen for the clarity and smoothness of the trebles; you want to achieve realistic high frequency response. This does not mean soft, rolled-off trebles (typical of too little tweeter output) or bright, hard trebles (typical of too much tweeter). Never advance the treble level past about 11:45. This is due to the tweeter's high sensitivity (96dB/1W/1m), which must be cut about 5 to 6 dB to match the midrange panel's 90 dB sensitivity. The electronic crossover bass level control is employed to match woofer levels to the mid/treble output. 

4. If your system is set up for triamping/triwiring, the midrange amp connects to the lower gold binding posts on the passive crossover box. The treble amp (or treble wire in a biamped, triwired system) connects to the upper set of binding posts (black and white plastic knobs). 

5. Don't forget you can influence the clarity and definition of the entire system by adding or removing putty from the passive radiator. Try taking off about 1/10 gram of putty from each passive radiator before performing the adjustments with the electronic crossover and passive crossover level controls, or right after you have optimized the system by making these adjustments. One tenth gram of putty is an amount that will fit under a fingernail, or rolled up, is about the size of a black peppercorn. In other words, a very small amount! 

6. Take at least one to two hours, making small adjustments on the system with familiar program material, to achieve best results. Remember do not elevate the bass column or mid ribbon panel off direct contact with the floor; both of these have had isolation mats installed on the bottoms so that the columns will not drive the floor, which muddies the sound. If the wiring from the passive crossover box to the five pin input jack on the bass column is too short, you can elevate the crossover boxes off the floor with standard Tiptoes or spikes (one application of these popular audiophile accessories that actually helps matters!) 

7. Place the power supply for the electronic crossover well away from any other equipment; there is considerable AC stray field. The crossover is equipped with an 8 ft umbilical for this reason. The power supply enclosure is quite large but also quite full of parts (480,000uF energy storage!).