Research

What must the component isolation system accomplish?
Obviously, it must support the components in space, not a difficult task. It must then individually isolate the supported components from all vibration. For GPA, the overall task was to create more user-friendliness, better environmental integration, superior aesthetics and higher levels of workmanship and fit'n'finish than existing designs.

What are we trying to protect the equipment from?
Clearly, airborne and floorborne resonance and exposure to self-generated mechanical vibrations from the other components. Lengthy measurements on custom shaker tables and accelerometers determined that by far the highest level of "vibration pollution" originates from the constant impact pulses of high-amplitude speaker-generated floor-coupled disturbances.

The more full-range loudspeakers become, with the ability to reproduce the lowest frequencies (and the higher their output levels of playback turn due to large rooms, increased listener distances or a simple desire to play things at realistic loudness), the more the most harmful large-magnitude low-frequency pulses propagate to and thru the equipment stand into the components via the subfloor.

Speaker-generated airborne vibration is next in magnitude, followed eventually and very marginally only by the low-level excitement of 60Hz powerline resonances in transformers and power supplies, and the after-effects of spinning CD/DVD drives and tape transports.

The difference between floorborne and self-generated resonance is like that between a spoken whisper and music listening at regular 80dB levels with peaks up to 95dB - you can't hear a person whispering even standing right next to you.

What is deficient in existing designs?
Using various shot-filled commercial examples of the "Solid Steel" school of designs that embody the principle of high-mass and rigidity (metal columns and struts, welded connections, various spike systems for floor and shelf contacts), our shaker table measurements quickly showed that regardless of mass and weight, these contraptions were highly ineffective at blocking and attenuating floorborne vibration. In fact, they were much better transmitters of vibrations than isolators.

• Many fixed/rigid designs couldn't accommodate larger/deeper components or those like certain tube amplifiers that need additional ventilation space.

• Spatial confinement further made access to cable connections or actual removal of the components from the system inconvenient.

• The appearance of the support structure was often not in keeping with the level of finish of the components placed in it.

• Some designs suffered from protracted and complicated assembly requirements.

• Those that used various intermediate cones/pucks/bearings caused extreme impracticality during component setup and removal. Often, these interfaces did not remain in place but were dislodged when power cords and various signal cables were attached.

• Many floor-coupling spikes were ill-equipped to provide the structural integrity for the intended weight to be supported, didn't come with proper locking features, were hard to adjust and often nothing other than modified soft 1/4" bolts with insufficient core diameter.

• As our measurements clearly showed, few stands offered any actual damping or true isolation capabilities.

What will be the best way to approach these problems?
An overview of current theories identified the following 5 approaches:

Mass: The common belief being that high mass is necessary to suppress the propagation of vibration. However, it is generally not understood how effective this approach is versus others and how much mass is required to achieve the desired results.

Suspension: Typically done with bladders or springs, this hangs supports from main structures to provide free movement. Highly desirable if the liabilities involved can be properly controlled with damping.

Damping: A native material function that inhibits and suppresses excessive excitement and the associated instability of oscillations. Common examples include a piano's felt dampers or a car's shock absorbers.

Coupling: [To link together] The recurring theme is to use cones for reduced contact area and increased loading to minimize the transfer of vibration.

Decoupling: [To reduce or minimize linkage] Commonly addressed with compliant or visco-elastic materials like Sorbothane that act as integral self-enclosed attenuation devices against vibration. Common examples include automobile and motorcycle engine mounts that are weight-matched and spring-rate tuned to individual applications.

Based on this survey, the design team came to the following Realization.