DIY speaker isolation base for a wood floor

My dual-layer iso platform Nirvana employs two very heavy masses 18x18 like granite or bluestone and two layers of springs. You can achieve extremely low resonant frequencies Fr with this set up, circa 1.0 Hz. Hel-loo! Total cost you ask, about $100. You supply the granite or bluestone. Cannot beat with stick.

Thanks for offering Geof.

Right. So there are two issues here, the speaker vibrating and the floor acting as a sounding board. In geoFFkait's example he is isolating the floor from everything above 1 Hz. So the floor is being isolated nicely. But, unfortunately the speaker is free to vibrate at all frequencies above 1Hz. Any vibration of the speaker is distortion. Some new designs like the Kef Blades and Magico subwoofers use drivers on opposite sides of very stiff enclosures so their forces cancel. This prevents the enclosure from vibrating as a whole. The best way for us to deal with both problems is to have a stiff well dampened floor. Concrete is ideal. A wood floor has to be very stiff then dampened with padding and carpet. The best way to keep the enclosure from vibrating is to spike it to a stiff well dampened floor. Force cancelling woofers like in the Kef Blades are ideal. 
Good work geoFFkait you have succeeded in making a bass distortion machine.