There are several methodologies at issue here; coupling and decoupling.
Based on my experience, I would think that the goal is to expiditously transfer the vibrations and resonance away from the speakers into the sub-flooring system.
To insert a small concrete slab, may or may not be of benefit. As rather than allowing the vibrations to evacuate into the sub-flooring system, you may end up trapping the the vibrations in the small platform to which the speakers are resting.
Unless your bass is so ill-defined and boomy or your house is so old that there is simply way too much bounce in the sub-flooring, I would suspect that your present method of spike/points under the speakers going hopefully through the carpet and resting on wood flooring should be sufficient.
One thing you might try before going down another path is check out StarSound.biz's Audio Points which some consider to be the best sounding in the business and the geometry is such that the points act as carpet spreaders to ensure complete contact with the sub-flooring.
-IMO
Based on my experience, I would think that the goal is to expiditously transfer the vibrations and resonance away from the speakers into the sub-flooring system.
To insert a small concrete slab, may or may not be of benefit. As rather than allowing the vibrations to evacuate into the sub-flooring system, you may end up trapping the the vibrations in the small platform to which the speakers are resting.
Unless your bass is so ill-defined and boomy or your house is so old that there is simply way too much bounce in the sub-flooring, I would suspect that your present method of spike/points under the speakers going hopefully through the carpet and resting on wood flooring should be sufficient.
One thing you might try before going down another path is check out StarSound.biz's Audio Points which some consider to be the best sounding in the business and the geometry is such that the points act as carpet spreaders to ensure complete contact with the sub-flooring.
-IMO