|Two Simple Facts
We begin then with two simple facts. First, the natural habitat of nearly all audio systems is extremely noisy. Second, whereas most music loving audiophiles are prepared to spend considerable sums on 'components' that they have reason to believe will improve music playback and their enjoyment of it, they are considerably more resistant to spending any appreciable sum to 'clean up the environment' or to minimize its impact on music playback. Taken together, these facts beg an obvious question: Why would individuals willing to spend small fortunes on interconnects, speaker cables, power cords and power conditioners -- to say nothing of the small fortunes that have been spent on preamplifiers, amplifiers, sources and speakers -- resist making an appropriate investment in resonance control?
Most audiophiles have no way of determining what an appropriate investment in resonance control would be - and for several very good reasons. First, most of us don't fully appreciate the ways in which a noisy environment adversely affects sound reproduction. Nor are we confident that we would know what to listen for in order to determine the relative effectiveness of alternative resonance control devices. It doesn't help that precious few audiophiles know how resonance control devices work or what the magnitude of improvement is likely to be in absolute terms; and no one has a common metric to assess the relative improvement of resonance control in comparison to other sonic improvements obtainable in principle by other audio system purchases.
Lacking an appreciation of both the underlying science of resonance control and a mature culture for sorting out differences in performance subjectively, and with virtually no meaningful prospect of implementing A/B testing in any case, most audiophiles remain skeptical about the wisdom of making any but the most modest investments in resonance control. Even those who are not skeptical of the ultimate value of resonance control cannot proceed because they lack the confidence necessary to proceed rationally. The first order of business then is to help sort out snake oil from science, mere furniture from genuine audio components whose contribution to good sound is unmistakable.
The Harmonic Resolution Systems Approach
The HRS M1R rack does not represent the only credible approach to resonance control. Our publisher, among others, is particularly fond of racks from Gran Prix Audio. I can attest to the high performance one can obtain from Finite Elemente's equipment racks. In time, I hope to explore how other equipment racks fare at controlling unwanted vibrations and to understand the science involved in various approaches; and ultimately to pass both on to you. But I know the HRS rack best and reporting on how it works and how well it achieves its goals is the best way I know of explaining what broadband noise reduction can mean for your system.
The HRS rack that I have had in for review, and which is now a permanent fixture in my system, stands 44" h x 23" w x 19" d, weighs in at 337 lbs and is decoupled from the floor by four metal cones that can be adjusted to level the rack system. It has four shelves, three of which are occupied by 19" x 21" isolation bases. Currently HRS offers four racks: two of which are four shelf/three isolation base models; and two of which are three shelf/two isolation base models. Both the three and four shelf units come in two sizes: one size accommodates the 19" x21" isolation bases; the other accommodates the smaller 17" x 19" isolation platforms. The bottom shelf in all units is a bay into which an additional isolation platform can be fitted. The bay itself has a wood veneered floor under which is located a resonance control structure. No isolation platform is required for the bay, but HRS testing indicates that an isolation base placed in the bay has additional sonic benefits. The isolation platforms are connected to the rack structure by a system of brackets whose position in the frame can be altered easily in order to change the distance between the platforms or to increase the number of isolation bases on the rack. Each equipment rack is finished in furniture grade wood veneers. HRS also offers painted finishes and exotic wood finishes with custom orders. The one I reviewed came in mahogany and an enormous amount of attention was paid to matching grain on all exposed sides of the rack. The general appearance of the rack is that of a substantial piece of beautifully finished furniture. The aesthetic is modern American. It looks like it belongs in a room with substantial furnishings. The aesthetic was perfect for our home and would be a much more challenging fit in our apartment, which is what I would call European angular.
For almost all of my listening I had a turntable on the top (first the Well Tempered Reference, then the Redpoint Testa Rossa XS and finally the Brinkmann Balance). As it happens, both Peter Clark of Redpoint and Lawrence Blair of Brinkmann were themselves so taken by the performance of the HRS isolation platforms that they have entered into separate relationships with Mike Latvis to provide custom-made platforms for their particular tables. Peter and Lawrence swear by the HRS (as do apparently an ever increasing number of high end manufacturers) and so asked that I review their tables on the special isolation platforms that Mike had produced for them. I accommodated both of them and so their tables each sat on product-specific isolation platforms within the rack.
The second shelf was reserved for my digital front end. That meant the Reimyo CDP-777 for most of the review process. The Exemplar universal player spent some considerable time there as well, and soon the Audio Note CDT 2 will take up residence. The third shelf was reserved for the preamp, which meant either the Shindo Monbrison or the Shindo Catherine two-chassis dual mono design. The bay was reserved for power conditioners (BPT Signature, Reimyo ALS -777, Shindo Mr. T - very briefly) and power supplies for the turntables. Amplifiers were placed on separate isolation platforms acting as amp stands placed on the floor. There was never a single component during all this time whose performance did not improve noticeably by its presence in the HRS rack and not just by a little bit either. To learn how I determined that, read on.
A three-part system
The HRS equipment rack is an integrated whole, but it will prove helpful for our purposes to distinguish among its three fundamental elements: the rack structure or frame; the brackets on which the platforms rest; and the platforms or isolation bases themselves.
To say that the HRS rack represents the state of the art in terms of the application of advanced mechanical engineering principles to resonance control in a real-world product would be something of an understatement. I spent hours on the phone with Mike Latvis who shared an extraordinary amount of technical information about the design of the HRS rack. I understood my share of the design concepts and the HRS approach to implementing them but I did not understand it all certainly not at first.
Fortunately for me, I have access to scientists -- in this case an engineer and a physicist -- at the two universities at which I work. I called on both to help me sort through the technical details of the HRS approach, from the choice of materials to the strategies for implementing theoretical findings in a real-world structure. My goal was to become sufficiently competent about the technical design in order to convey how the rack achieves broadband noise reduction to you, the potential end user, in a way that would help make products like the HRS rack credible without revealing anything like a trade secret. An unintended byproduct of my discussions was that I got at least one scientist so interested in Mike's design that he came by the house for a long and very admiring look and an even longer listen. Mike's design not only secured his seal of approval; the long listen may well have stimulated the loss of yet another otherwise productive life to audiophilia.
There's no such thing as good vibrations
The Beach Boys may have sung the praises of good vibrations but when it comes to audio playback systems, there may well be no such thing (except perhaps for those occurring between a phono stylus and an LP groove). We can distinguish between structure-borne and air-borne vibrations. The main differences between the two have to do with the manner in which they are transmitted to your audio system, and not the source of the vibration itself.
As I noted in my prior review of the HRS M3 Isolation Base, the sources of vibration are many: household appliances -- especially refrigerators, dishwashers, washers and dryers -- as well as video and audio components. The worst offenders are loudspeakers. Loudspeakers literally shake the room, which is the environment that the rest of your system is situated in. The vibrations created by the loudspeaker, including those internal to it, are fed back into the system through the room only to resurface as part of the output from the loudspeaker, and so on in a vicious cycle. Worse, given that most structure-borne vibrations in audio systems have broad frequency ranges, the prospect of finding matching natural frequencies with the rack system and audio components is high; the consequence is that non-musical energy can be significantly amplified.
The phrase 'air-borne vibration' refers to any source of vibration within the audible range of the playback system. Again, the greatest sources of air-borne vibrations are loudspeakers. These vibrations reach the outer skins of components and the equipment racks, floors and furnishings that support those components. Some of this energy is dissipated, some reflected and the rest is transformed into mechanical vibration that, like structure-borne vibrations, wind their ways through your system, often being amplified along the way.
The main problem with vibrations is pretty simple. They constitute non-musical information degrading signal quality by loss, masking or through unnatural addition that can be spread broadly over the frequency range. In your playback system, the likelihood is great that you will end up damaging signal quality by amplifying essentially non-musical information e.g. distortion. The basic idea is simple to grasp. An audio or video signal from a source component exists in a noisy, vibrating environment; worse, the components in the chain are themselves, to varying degrees, noisy as well. The noise is transmitted and causes errors throughout the system and is likely to be amplified or inter-modulated along the way.
Non-musical energy creates smearing which in turn obscures low-level detail. Musical attack and leading edge are blunted, harmonic structures inadequately resolved and decays truncated. Bass, which is hard enough to reproduce accurately under most conditions, will be less resolved and tuneful, and overall accuracy and musicality will be reduced. Timing suffers dramatically. High mass components in particular -- think many modern turntables -- that are inadequately isolated will sound sluggish. There is no part of music playback that is unlikely to not suffer at the hands of unwanted vibrations. In a word, music will be inaccurately portrayed. The return on the investment you have made in your audio system will be far less than it might otherwise be.