A little more than six years ago, I reviewed and subsequently adopted the Pierre Lurne record clamp as my reference after a rather exhaustive search for a clamp/weight that would enhance the sonics of my Rockport Sirius turntable. Initially, I would have said, if asked, that given that the Rockport has a well-designed vacuum hold down mechanism, there was little added benefit to a clamp or weight. As I explain below that conclusion resulted from a fundamental misunderstanding of what a well-designed clamp/weight can accomplish. In any event, until very recently, I have continued to use the Lurne. In the interim, Pierre decided to retire so the Lurne clamp is no longer in production. I have tried a number of other clamps/weights since then, but none surpassed or equaled the Lurne, at least in my system. The closest, at least until now, was the Stillpoints weight which is expensive but very good.
Why Would You Need to Use a Weighton A Turntable That Incorporates a Vacuum Hold Down Mechanism?
A turntable system is simply a mechanism for converting the mechanical energy supplied by the turning of the platter by the motor into electrical energy. The conversion occurs when movement of the stylus generates the electrical signal. All movements of the stylus are converted to electrical energy, not just those related to musical information impressed into the record grooves. Any converted movement not directly related to the musical information is detrimental to the recreation of the musical event. In many instances, the motor creates more energy that is needed to turn the platter. This energy must be dissipated by the turntable. Much of it is transmitted through the bearing and dissipated as heat. Some is undoubtedly absorbed by the platter. A related problem is that not all motors are created equally. Some exhibit cogging, and other non-linearities. Even if the motor is well designed, the motor may be affected by the distortion products contained in the electricity used to feed it. In the main, the design of the turntable, if properly executed, should minimize this type of noise (i.e. that caused by distortion products in the power line); however, even in a turntable like the Rockport Sirius, it is never completely eliminated. A properly designed record weight/clamp can act as an energy sink for some of this energy by providing a low impedance path for energy to migrate away from the stylus as well as a mechanism to convert that mechanical energy into heat. In the case of the Orbius, the designer has chosen to use a material with a mechanical impedance close to that of vinyl for the outer ring of the clamp that contacts the record and tungsten at the center of the clamp to serve as the energy sink. The Orbius is also available with various other materials in place of the tungsten such as wood which significantly reduces mass allowing the use of the Stabilizer on a wider variety of turntables.
The record weight is also designed to address another problem inherent to the vinyl medium, – records are seldom flat. In many instances, they are warped. Unfortunately, as the stylus moves over these warps, the movement of the stylus tracking the warp can induce an electrical signal from the cartridge that is often close in frequency to the resonant frequency of the arm/cartridge used and the combination can generate distortion. These warps also contribute to the premature failure of the suspension of the cartridge. A further benefit of flattening the record is that it brings it into intimate contact with the platter which, if properly designed, will allow spurious energy in the vinyl generated by the passage of the stylus to be dissipated. This effect can be rather significant with thinner records and is another area which the Orbius is designed to address.
It is perhaps worth noting that the Orbius design incorporates two other features that can be quite useful: 1) an extremely accurate bubble level and 2) a strobe which when used in conjunction with an iPhone’s movie mode allows the user to accurately monitor platter speed.
Moving into the issue of how the Orbius affects the sound, the following comparisons were between my reference Pierre record clamp and the Orbius Stabilizer used interchangeably on my Rockport Sirius turntable with the vacuum hold down engaged.
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