Aether Audio URS-VF

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 Vortex Filter
Amp to Loudspeaker Modules

The Vortex Filter represents a new and innovative solution engineered to reclaim an area of audio system performance that heretofore has been shrouded in mystery and seldom (if ever) addressed within most engineering circles. As a result, no other conventional audio cable or accessory alone can achieve the sonic benefits commonly experienced by the inclusion of Vortex Filters in your cherished audio playback system. Typically, users can expect the following:

  • An elimination of “electronic fog” or “haze” and/or the effect of a “veil” having been lifted from the system
  • Significantly increased levels of micro-detail and resolution
  • A richer, more palpable rendering of delicate harmonic texture, naturalness and overall realism
  • Improved bass definition, speed and authority
  • Improved sound stage width, height & depth
  • More succinct imaging and instrument localization


The Ultimate Reference Series Vortex Filter

The URS Vortex Filter Amplifier-to-Loudspeaker Module is a full-featured device constructed with the best components available. It is a totally passive (no batteries or other power sources required), monaural unit (two units required for stereo operation) that is simply inserted into the signal chain between a given amplifier output channel and its associated loudspeaker. An additional feature that is unique to the URS-VF alone is a user adjustable switch that allows its Zobel Network feature to be configured for achieving the best possible match between your amplifier and loudspeakers.

 Specifically, the URS-VF was developed to address the Phase-related and Back-EMF induced distortion artifacts that arise within the amplifier/cable/loudspeaker section of any high fidelity audio system.  Within the Vortex Filter are separate “Smith Cell” & “Zobel Network” sections that have been specifically designed to individually address each of these unique classes of distortion.The URS-VF can be ordered in stock form as shown in the above photograph, or or it can be custom-built to your individual requirement, including your choice of Binding Posts, Binding Post locations (e.g. Inputs and Outputs both on one side), and even alternative end plates in the form of “L Brackets” for mounting the module to any horizontal or vertical surface you wish, such as a wall or the back of your loudspeakers.

Reflected Energy Damping Network:

As stated, within the URS-VF are two separate sections, with the first section being the “Zobel Network. This network of passive components is designed to correct for secondary distortion artifacts that typically arise within the amplifier/loudspeaker interface.  This specific distortion mechanism is a well-known phenomenon that results from an ongoing process of energy storage and release that takes place in virtually all loudspeakers.

Commonly referred to as “Back-EMF” (electro-motive force), this "reflected" energy presents to the amplifier a complex set of simultaneous tasks to perform during normal operation.  While the amplifier attempts to amplify and drive the loudspeaker with an ongoing signal from the source signal present at its Input, the loudspeaker simultaneously releases energy that has been stored in the form of Electrostatic and Magnetic (EM) fields within the loudspeaker drivers and crossover network. This stored EM energy is the result of previous signals that originated from the amplifier, such that micro-seconds later in time the EM fields “collapse,” transforming the field energy into a voltage that then attempts to drive electrical current back into the amplifier.

This Back-EMF is then "seen" by the amplifier at its Output terminals, and because it is not present at the amplifier’s Input, the amplifier interprets this Back-EMF voltage as an "error signal.” As a result, the amplifier’s Negative Feedback (NF) loop then attempts to “correct” the error by eliminating it, or at minimum, dampen (reduce) it to some good degree. This “damping” effect is commonly referred to as the amplifier’s “Damping Factor.” Most all modern amplifiers employ some amount of NF in order to achieve a reasonably high DF for the express purpose of controlling (as best as possible) the diaphragm motion of the connected loudspeaker drivers (woofers, tweeters, etc.) in order to reduce distortion.

In any case, as a consequence of trying to perform these two simultaneous tasks PLUS the fact that the Back-EMF signals are delayed in time or "out of phase" with respect to the new source signals present at its Input, the amplifier will often create new "errors" as a result of a "less than perfect" response in its attempt to eliminate the loudspeaker Back-EMF errors.  Either that, or if the amplifier does not employ any NF whatsoever, then it will simply "ignore" these error signals altogether and thereby allow the loudspeaker to "ring" or resonate at the given Back-EMF frequencies.  Neither response is a good thing for high fidelity performance, so a way to differentiate the "good from the bad" and attenuate only the bad signals would most likely improve fidelity to a considerable degree.

By reducing the Back-EMF induced “overburden” on the amplifier via selectively attenuating only the reflected loudspeaker signals, the Vortex Filter’s user-adjustable Zobel Network effectively works to improve overall system performance.  The resulting sound is typically perceived and described as being "softer" and less fatiguing at mid to high frequencies without loss of detail, while also one of increased system micro-dynamic resolution, sound stage depth and image localization.

In order to accommodate the needs of the majority of systems, the URS-VF incorporate three (3) different user-adjustable sets of Zobel Network components that are specifically selected to perform the function of attenuating only the undesirable Back-EMF error signals.  Seeing that there are three primary classes of amplifiers, the type and values of components needed to perform this function optimally for each amplifier class have been combined to form three independent, switch settings (see table below).

With each successive switch setting in the clock-wise rotation, the network values increase in their potential effectiveness.  In addition, they also increase the likelihood that a small amount of undesirable attenuation of the source signal in the ultra-high frequency region (10kHz and above).  This aspect is particularly true when being used with amplifiers exhibiting higher values of output impedance, such as is common with Singe Ended Triode (SET) amplifiers.  Class "B" or Push-Pull tube amplifiers, and low powered Solid-State amplifiers usually exhibit somewhat lower output impedances than the SET type, and are therefore more immune to unwanted high frequency attenuation.  Finally, mid to high power Solid-State amplifiers usually exhibit the lowest levels of output impedance and are therefore the most immune to high frequency attenuation by the various URS-VF settings.

Therefore, the switch positions outlined in the table below are only guidelines for use and it is recommended that the user experiment for themselves to find the best setting for their system.  Please keep in mind that the SET type amplifier is most vulnerable to high frequency attenuation at higher switch settings while Solid-State amplifiers are the least vulnerable, such that they can typically accommodate any of the settings without concern for high frequency attenuation.  With these guidelines in mind, it is then a simple matter of adjusting the switch to achieve the most desirable effect for your listening preferences.

The Smith Cell:

Representing the other section of the URS-VF, the Smith Cell was developed to address very unique and obscure forms of distortion artifacts that typically manifest, to one degree or another, in even the most pristine of audio systems.  In fact, this area of system performance is a matter of much debate in the audio world, and there are many that have not understood and/or recognized its existence.  These forms of distortion are rooted in two primary areas within the audio system:

  • The microscopic realm of electron interaction with the very atomic and molecular framework of conducting metals and materials.
  • The complex secondary effects that occur within circuit components and conductors upon their exposure to electrical AC voltages and currents.

     To be succinct, the proper terminology regarding item #1 above is that of the"Phonon" behavior within conductors, and how such phonons interact with electrical current as it flows through the conductor.  Phonons are defined as "virtual" particles and can take the form of a single atom, molecule or groups thereof, or a single crystal (termed "Brillion Zone") or group of crystals.  Even impurities in metals or other materials can be viewed as phonons.  One will note that it is via successive phonon energy transfer that thermal energy conducts and mechanical vibrations transmit through a solid material

    While the subject is too deep to adequately cover in this article, just as one example we would make note that phonon behavior is commonly believed to be one of the primary sources of "Flicker noise" observed in electrical systems, and is also known as "Pink noise" (1/f noise) that is observed in biological systems, Gravitational Wave Astronomy  and throughout the physical universe.

    The only real question is one of its audibility with respect to phonon activity.  As far as its "standard" form is concerned, observed as the noise produced by common resistors and other components, it is well-known and must be considered in low-noise amplifier design. So at least on one level we know that it is audible.

    Going beyond that though, it is our contention that said phonon behavior and its interaction with and subsequent modulation of electron current flow, it also manifests as a form of "Phase-Noise/Distortion" and as such represents a more subtle source of phase-related error artifacts in audio systems. Consequently, we also suspect it has been stealthily operating behind the scenes of the audiophile cable debate all along.

    Regardless of their source though, all forms of Phase-Noise/Distortion impart a sonic effect analogous to that of a video camera that is "ever so slightly" out of focus, such that fine musical details and subtle harmonic timbres become slightly blurred and less well-defined.  For further reading and in-depth analysis of the subject, please review our white paper:


    There is also a type of “Active Phase-Noise/Distortion” at work in all systems, and the URS-VF was designed to address it as well. For further details regarding it’s source we would refer you to the following section of this website:

    n order to significantly reduce (if not totally eliminate) these two forms of phase-related distortion, we have developed the "Smith Cell."  It relies on a very unique application of materials in a configuration that prevents signal current flow from directly interacting with them, while at the same time allowing these same materials to strip away both active and passive forms of Phase-Noise/Distortion at the sub-atomic level. System performance gains are manifest from the deepest bass up into the higher mid-range frequencies, with typical observations being that of deeper and tighter bass, increased tonal accuracy and realism, greater micro-dynamic resolution, a wider and deeper sound stage, and improved image localization.

     Another observation many have made is that system performance is no longer as highly dependent on the quality (read: expense) of the speaker cable formulation being used.  We as well as others have found that with the URS-VF inserted in the system, more common and lower cost cables provide nearly the same level of performance as their costlier and more exotic counterparts.  It has even been reported that common "lamp cord" provides very sufficient performance when used along with the URS-VFs. 

    In fact, it has been claimed that a system employing the URS-VFs and lamp cord for speaker cabling usually sounds better than the same system using exotic cables but with no URS-VF installed.  This all makes a certain amount of sense when one considers that the very action of the Smith Cell is to ameliorate the effects of phonon induced Phase-Noise/Distortion, which is most likely one of the many factors differentiating one cable type from another.  If one eliminates the fundamental distortion artifacts that given types of similar system components induce, then one also eliminates the primary difference between those different components.


    The URS-VFs are constructed of the finest materials which include Mundorf Silver-Gold alloy for all internal conductors and quality Gold-plated Binding Posts for both Input and Output connections.  The addition of 1% gold to the silver used in the Mundorf material has not only been observed to offer the best audible results, but is also based in solid scientific principles.  Gold exhibits the highest level of “Electronegativity” of any commonly used metal for audio applications.  Electronegativity is the property of ab atom to "draw" or attract electrons towards itself, and seemingly, this effect helps to further facilitate the action of the Smith Cell.  While this among other claims are yet to be proven scientifically, our observations from extensive listening tests thus far indicate it is the best conductor for use in the construction of the Smith Cell/Vortex Filters.


    Seeing that the URS-VFs are totally passive devices, no forms of external power or batteries are required for their operation.  Installation is therefore a simple matter of inserting them either at the speaker end of your existing speaker cables and then using a short piece of "jumper" wire to connect their output to your loudspeakers, or the reverse by placing them at the amplifier end of the speaker cables and using a jumper to connect them to the amplifier. 

    As stated above, we have found that the quality of the jumper wire is not particularly critical. Therefore, we provide a 1-meter length of standard OFC copper cable terminated with Spade Connectors at each end.  If you prefer, (at additional cost) custom jumpers of specified length can be provided that are constructed of other materials of your choice, such as Ribbon-foil or Litz Wire conductors, Banana Plugs instead of spades, etc.

     Below is a table demonstrating the various switch settings that are provided.  Again, you will note that they are identified by the class of amplifier being used in the system.  While these are only guidelines, we highly suggest that you start with the setting that is associated with the type of amplifier being used.  If after extended listening it is determined that the ultra-high frequency range seems to have been "softened" a bit too much, then moving the switch to the next lower position would be the logical response.  This process should be repeated until no such loss of high frequency performance is noted.  Once achieved, this then becomes the final setting such that no further adjustment is needed.

     As a side note, close attention should be paid to determine whether any observed loss of high frequency energy is truly one of the source signal being slightly attenuated, or rather a result of lowered high frequency distortion.  Commonly, audiophiles are "deceived" into thinking that much of the "air" and "detail" they hear are a result of accurate reproduction, when in fact such audible information is often a result of high frequency distortion that the human hearing mechanism is unable to detect as such. 

    Therefore, if at first the higher frequencies seem attenuated at a given switch setting, listen closely to determine if the sound of brushed cymbals remains natural and extended.  If not, then lower the switch one position and listen again. If lowering the switch setting to its lowest level does not restore the desired high frequency presentation, then welcome to the revelation that what you once thought was true detail and extension was in reality… only high frequency distortion.

    Please note that the switch should not be adjusted for variations in source recordings, as it is not intended to be used as a "tone control."  Such use will only lead to confusion as to which setting is truly optimal.

    Finally, the best way to determine just how much improvement the URS-VFs provide is to place them in your system and listen for at least 20 hours over an extended period of time.  If possible, allow them to "burn-in" for at least 24 hours before your initial evaluation.  You may or may not observe a significant effect at first, but continue to listen for the better part of two weeks.  Then to find out just how much difference they are truly making, simply remove them from the system and listen again.  As many find, you will likely be a bit amazed just how much you miss them and will want to return them to the system immediately.

     Please be aware that as the table below indicates, regardless of the switch setting, the Smith Cell section is ALWAYS engaged as long as the URS-VFs are inserted in the system and cannot be defeated without removing them.  You may find as others have on occasion that Position #1 - "Smith Cell Only" – provides the most satisfying performance and is all that is needed.

     Happy Listening!