Before you pursue a rack system, it is important to determine what you want the rack to do. There are three distinctly different philosophies that must be understood and then you must decide which one you wish to pursue.
The three philosophies all have value, and all three have shortcomings. These are wooden /furniture shelf or cabinet, mass loaded steel or light and rigid.
The furniture is the wooden rack that will potentially have the highest WAF and can either hide or display your system. An all wood rack can be temping because of the ethic appeal, but in general a furniture type rack is neither light and rigid or mass loaded. These tend to have slow, bloated sonic characteristic yet can be excellent at taming overly bright systems. These tend to be the less expensive solid state system, and often the very best choice will be the muted characteristics of a wood/furniture rack. Do not however expect to receive the best imaging, transparency, high end extension or tightly defined solid bass. A wood/furniture type rack is generally not considered audiophile level.
The second type is the mass loaded. These are generally hollow metal posts with sand or lead shot inside the posts. These systems are likely to have shelves made from MDF, wood, acrylic, stone and composite materials. The philosophy is that vibration is drained from the component through footers, often rubber or through cones of lead, brass, composite, wood or most anything imaginable. In theory the vibration is stored in the mass, and if enough mass is available the vibration will affectively be dispersed. The mass loaded system is probably the most used audiophile level rack mostly because it has been around the longest.
The theoretical problem with mass loaded systems is if there is not enough mass to properly store the energy, it will be released, hopefully into the footers of the rack and into the floor. Many people believe this energy is re-released into the components in the form of vibration. The problem here is this is not a musical vibration and it is not in proper timing.
A poor rack system will allow a component to vibrate and in theory this vibration is heard through a high end system. But at least the vibration is timed with what is happening. If a high volume passage is vibrating the rack or component, micro or macro, the distortion created will correspond with an event. In the mass loaded system, the vibration may be released later, causing a new vibration to affect the sound. This may come at a highly refined period in the passage, causing a blurring or smear of what we here.
I believe the only way to properly execute a mass loaded system is to have a great deal of mass in every place possible. The shelf needs to me heavy, stone, steel, lead and something sandwich??? The frame need to properly couple to the shelf, and the frame then adds storage through its lead or sand mass. This must then be properly drained into a floor, and it should be a floor with more mass storage potential than the rack, meaning it would be best used on a concrete floor. The floor then becomes an extension of the mass loading, so coupling the rack to the floor is also important. I would be speculating, but if it was possible to bolt the rack to a concrete floor, the floor would be the additional mass required to successfully achieve the goal.
The third method is the newest and is the least understood, and possibly the most continental. In theory the vibration within a component is sent to a cone. The wide portion of the cone is coupled directly to the component, preferably at a structural element. The vibration, now affectively coupled, is send to the support shelf. The cone and shelf must be rigid, with little storage potential. Steel, brass and titanium are often used for cone material in the light rigid system. Wood, carbon fiber, lead and composites all store in comparison to the metal cones. The shelf can be either a fabricated light rigid product (Neuance for example) or glass and possibly metal if ringing can be controlled.
Generally speaking MDF and wood should be avoided again for their storage potential. The shelf can either then be directly in contact with a light rigid metal frame. (Apollo© is an excellent affordable system that works nearly as well as Mana©, which many feel is the ultimate in light rigid.) The thinner the frame the less storage potential and the faster it can transmit vibration. The idea is to then have the vibrations moving within the frame drain through points to the floor. In the event of concrete, the floor again has limitless storage potential. In the event of wood, the floor system has some potential to release these vibrations back into the rack. I believe this is where a bearing type product can be useful. The concept with bearings is to de-couple from the floor (or shelf) through vibration of one (or multiple) steel balls. These balls are in a cup (or trough) so that for vibrations from the floor (or shelf) to create vibration it must vibrate uphill to create movement (vibration) for a vibration to in effect lift a component or rack it would have to be very large, far larger than the vibrations we need to eliminate.
If you have the ability to weld, an excellent rack on the Mana© model. This would require small steel angle irons and threaded points made by grinding steel bolts.
I have spent over eight years testing and developing a very elaborate isolation system based on the light and rigid concepts. I have posted an in depth descriptions with photos at Audiogon as one of my systems. Please look at that and if I can be of assistance send me an email.
As always, these are only my experiences and observations. Others have had success with the other systems, but in my experience the light and rigid, quick vibration dispersion sounds the best. Meaning very quick, tight and extended bass, very clear imaging, smooth and extended highs with little smear or fuzziness. The leading edge of notes is sudden and crisp. Midrange of course is excellent with great imaging, focus, depth and definition.
jd
