Turntable isolation platforms

I look at vibration control through an RF impedance matching background. Spiking heavy speakers or platforms improves sound by rejecting high energy bass frequency vibrations in a suspended wood floor moving up into the component or speaker.

Varying pressures in the floor and around supporting beams due to concentrated weight on spikes causes diffraction or reflection of sound, stopping travelling waves in the wood medium moving up the speaker or component. An abrupt change in density is a fraction of bass frequency wavelengths, rejecting sonic conductance which minimizes cross talk between woofers from left to right speaker or speaker to component. Bass frequencies have the most energy and can morph into higher frequency resonance in cabinets and audio racks. 

That is just the start of treatment as I understand it. Performance improves if the fraction of vibration that finds it way up the feet or leaving the feet is attenuated as loss or sound absorption through the use of rubber, sand, isolation feet or platforms - whatever provides wideband absorption of vibration energy.

Basically you want to minimize reflection which is return loss in RF world by matching impedances. That is density and stiffness for maximum sonic conductance of materials. That's how cones work to pull high frequency vibrations out of components. Bass frequencies leaving speakers are best treated with loss through isolation since energy is high and will reverb through the floor. Higher frequency energy will not cause trouble in the floor, but should not be reflected off the isolation footer back into the speaker or component. 

Antenna are tuned or impedance matched for minimum return loss. If we use loss to extend bandwidth and minimize return loss , gain suffers. Fortunately, using loss in vibration control can improve performance with no downside since we are not trying to transmit vibrational energy through the floor at same time.

We're all talking about the same thing here. I've just provided a alternate, general way to understand what's going on, not just with turntables but speakers and components with noisy transformers as well. Mass on spring works well at low frequencies because of bass energy loss in the spring. Sand is likely needed for the high frequency isolation through absorption.

If you place a lightweight platform on spikes on a suspended wood floor without carpet, I doubt your going to get low frequency isolation.

That gets to my point, the floor is acting like a diaphram which has to have relatively even movement of soundwaves to be an effective transducer. Place a heavy weight in one spot and you have a node or lower energy zone. Sound waves traveling through the floor are reflecting off the perimeter of that weighted floor spot and travel around it or through supporting beams to other sections of the floor that allow vibration. It's like a large scale piezo-electric buzzer for bass.

Cones or vibrapods work on components because weight is concentrated under the metal chassis effectively conducting or draining vibration out of the component. Unlike the floor, the metal in the chassis doesn't change density near the cones. Cones work best with lossy plinths that dissipate energy.

The effective channeling, isolating and dissipation of vibration energy can be achieved by knowing when to minimize boundary reflections and when to incorporate loss. It's all wave energy, highly similar to RF.

brotw70

Ok, had to look that up. Mass on spring looks effective for isolating turntables through other means. I'm more interested speaker and component vibration solutions that drain sources of vibration to the floor. Haven't seen many spring solutions for those. I think springs just solve the floor moving up and down problem rather than lateral.