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The Stillpoints ERS Cloth

Stealth Invisibility for Your Audio System

Paul Szabady

9 March 2003


Electro-magnetic/Radio Frequency Suppression material.
Price: $19.95 per 8" 12" polyester-backed sheet.

2660 County Road D
Woodville, WI 54028
Telephone: 1-800-830-1575

One of the ironies of high performance audio systems is that the very technologies that allow them also create side effects that interfere with their performance. We are surrounded by a technologically created invisible soup of electromagnetic and radio frequency interference that each new generation of electronic products only thickens. One need only think of the proliferation of technologies and products that have occurred in just the last 20 or so years to grasp the scope of the problem. Home computers, CD players and the cell phone are just the tip of the iceberg. Whether generated internally by the specific component, picked up antenna-like by house wiring and cabling, or simply plucked from the Ether, the potential for disruption has never been higher.

Audio designers, of course, have long been aware of the effect of EMI and RFI on their circuits. A prime original rationale for separating preamps from power amps in the Tube Era was to remove delicate circuits from the proximity of interference-causing transformers; the increased contemporary use of outboard power supplies stems from this same awareness. The choice of pursuing wide-bandwidth designs was often made with awareness of an increased potential for RFI. The fine art of circuit layout and internal chassis positioning, along with chassis material choice, reflects attempts to free a design from susceptibility to parasitic EMI/RFI infestation. Except for those unfortunate enough to hear unwanted radio, CB or other transmissions break through into their systems, the sonic effect of this soup passes mostly unnoticed, or is misinterpreted as a flaw in a component or in the overall system.

There have been a number of products over the years to deal with the problem, the most common being ferrite rings to clamp over AC cords and interconnects. The UK's Peter Belt produces a controversial series of products that are designed to affect the environment and listener rather than the components themselves, reasoning that swimming in this polluted electronic soup negatively affects the listener's physiology and thus corrupts and distorts his perception. Of course one could put one's components inside a Faraday Cage, a kind of Maxwell Smart "Cone of Silence," to keep contamination from entering. Following Belt's thinking, the listener would need his own Cone of Silence, leading unavoidably to the image of Maxwell Smart and The Chief yelling "What?" back and forth to each other from their isolation capsules. The new ERS (Electromagnetic/Radio frequency Suppression) material aims to offer effective, easy to use and inexpensive solution to the interference.

The ERS material is designed to dissipate EMI and RFI and thus keep it from entering and affecting audio components. The ERS' dissipating elements are suspended within the basic ERS 'Stealth Cloth:' an 8" 12" gray-colored sheet backed with polyester on both sides. It can be cut to size to fit its application. The cut edge will be conductive, however, so care should be taken if used inside a component. A pressure-sensitive adhesive backed cloth is also available ($29.95 per sheet) for those who would prefer to place the sheet inside the component's case. To use one simply places the ERS cloth over the component or offending source. One can also wrap and swaddle a component. Cutting it into long strips allows wrapping interconnects, power cords and speaker wire. Significantly, the product has enormous OEM potential for manufacturers: reports from the ERS launch at CES showed equal enthusiasm from equipment designers and from consumers. The ERS cloth is so inexpensive that it feels almost foolhardy not to try it.

Although RFI and EMI are all pervasive, one's geographical location can alter intensity and density. Moreover, rural dwelling does not guarantee immunity, as a demonstration of the product at the distributor's rural Wisconsin residence pointed out. Reports from users living in the Twin Cities' Death Zone for interference, a suburban area near the cluster of broadcast towers that serve the metropolis, were near ecstatic at the improvement. My own locale is urban, facing two of Minneapolis' urban lakes and about 7 miles northwest of the Twin Cities Airport.

I tried the ERS cloth on 3 different systems on 3 different levels in my house, from basement to bedroom loft. I placed it on and under components, wrapped interconnects and power cords, covered and also wrapped outboard power supplies, AC-power junction boxes, and even cut the ERS to use as a turntable mat. Because of the number of components tested, I did not try the ERS inside components (except for one brief assay), nor did I attempt to treat individual sections within a given component, e.g., wrapping the transformer inside an amplifier to nullify its effect on the surrounding circuitry.

Investigating the effect of the ERS was an intriguing experience, dispelling some assumptions, affirming others and clarifying the areas of the greatest contamination and their access points into my particular systems and components. Rather than recite a litany of the effects on the specific components, I would rather offer what similarities were common throughout.

The ERS' overall effects, though subtle in my systems, were nonetheless highly significant. There was a noteworthy reduction in artificial brightness and hardness, along with a reduction of low-level background electronic 'hash.' The sonic results of this improvement were a more natural and correct reproduction of instrumental timbre. Instruments that had sounded slightly false without the ERS sounded correct when it was applied. The effect was at first most obvious on midrange instruments but also extended into the bass, where the timbral improvement was joined by increased definition and control. High frequency percussion was also improved, with higher resolution and more natural portrayal of percussive colors.

The changes sounded like a significant reduction in the amount of intermodulation distortion, a lessening of non-musically related additions to the signal. Since this is also partly the model for explaining the effects of EMI/RFI on components, theory and perception nicely dovetailed. Because intermodulating distortions are not related harmonically to the signal, the true timbre of instruments is distorted. False additions woven through the sonic fabric skew the harmonic structure of the note, distorting its identity and source. Incorrect reproduction of volume levels and dynamic changes are also a by-product. Familiar audiophile gremlins such as harshness, edge, grain, brightness and hash all yield to this explanation. Although this model does not exhaust EMI/RFI's effects, it does offer a simplified anchor to some of the ERS' sonic results.

Not all applications benefited equally: some instances showed no perceptible improvement. No big deal though, I simply kept the ERS where there was. In my own specific set-ups, I found the most obvious improvement over phono sections, outboard power supplies, AC cord junction boxes and over transformers in pre and power amplifiers. I was surprised to find its use as a turntable mat on metal platters significant. None of these results should be set in stone however; audition and experimentation are absolutely essential within the context of one's system. The ERS' ease of use and low price makes this painless. It is worthwhile to experiment extensively, trying the ERS in places where one might assume there to be no problem. In my case, the ERS' effectiveness over AC cord junction boxes was almost lost due to my initially ignoring them as a potential offender.

Listening to music with an ERS treated system was refreshing. Without having to listen through the distortion of EMI/RFI, I found myself using less perceptual energy to identify instruments and their location, and could devote complete attention to listening to what they were doing. Less distracted by sound, I could yield to the music. Freed from artificial brightness, listening sessions were limited by my appetite for music, rather than by listening fatigue.

The Stillpoints ERS cloth is a significant product. Its potential in audio design from loudspeakers to electronics is limited only by the imagination of the designer. My interest is piqued to hear new audio products incorporating the ERS material. Since the most common complaint about the sound of existing systems is harshness and artificial brightness, lowering EMI/RFI's contribution to that complaint is a genuine boon. Congratulations to Stillpoint's Paul Wakeen and Larry Jacoby for bringing such an effective and inexpensive product to market. Thanks guys. Highly recommended.






















































The Stillpoints ERS Cloth