I got some questions on how the floor is floated. So I dug up some pictures from last year.
First you see the outer shell which is the basement floor, with a 20cm wide perimeter of Regufoam, 5cm thick. The Regufoam used is calculated based on all the weight of the two bunkers that will push on it so you get a certain pressure and it acts as the spring in a mass-spring-mass system.
If I understood it correctly (Thomas, please correct me if I am talking rubbish here
) the resonance frequency of the final system (when all the weight is in) lies around 7-8Hz. This too make sure we're well enough below the lowest bass frequencies.
The second picture shows the concrete slabs put on top of it. The PVC pipes you see are to vent the locked-up air between the Regufoam. If we wouldn't do this, the air would act as a spring too, messing up the system...
Greetings,
Dirk