The problem you face with springs is the same old problem - the springs need to be widely spaced, so that means you would need some structure to allow the springs to be placed in a wide pattern, pattern outside the dimensions of the speaker footprint. Otherwise the speakers will topple over.
It is feasible to construct a large 3x3 CROSS that the speakers sit on with springs of the correct stiffness under the CROSS at each of the 4 corners. Tricky but feasible. That’s a DIY Townshend Podium. But something that heavy is dangerous on any support IMHO.
It is feasible to construct a large 3x3 CROSS that the speakers sit on with springs of the correct stiffness under the CROSS at each of the 4 corners. Tricky but feasible. That’s a DIY Townshend Podium. But something that heavy is dangerous on any support IMHO.