Anyone try Cerapucs under full range speakers?

Decoupling. Even on a cement slab decoupling is better because the cement slab is moving, too, just not as much. Also, because decoupling reduces any tendency for mechanical feedback in the system. 

We call that a trampoline floor. So, in effect, you are coupling the speakers to a moving floor, a vibrating floor. Don’t worry about the cavity resonance. You have enough to worry about already.

mijostyn - Actually that’s completely incorrect. Placing speakers on springs reduces cabinet vibration. Didn’t you watch the video? Mass-on-spring isolation systems work in both directions. Vertical and horizontal forces - regardless of their source - are reduced because the springs allow ease of motion of the speakers in the vertical direction 🔝and the horizontal plane 🔛. The vertical direction means both UP and DOWN. Ease of motion is generally accomplished by employing an iso system with very low resonant frequency Fn. That’s the physics, in a nutshell.

Also, since mass-on-spring iso systems are extremely effective as the vibration frequency increases, the spring based system is extremely effective >99.9% in reducing cabinet resonances, which will always be much higher than Fn. This means the internal wiring, crossovers and cable connectors are isolated by spring-based systems.