Terrible Booms

Stani19, Describe the construction of your floor for me. You mentioned Parquet with voids below? Is it Parquet on a wooden joist floor? What is the width of the joists 10"? What are the dimensions of the room. Is there a basement under the floor and is it finished or unfinished? It sounds to me you were on top of the problem to begin with. I was involved in two situations were the floor was the problem. In both cases the joists were too small for the span they covered and the floors bounced. We fixed it by putting beams across supported by lolly columns below.  One floor was actually sagging over an inch in the middle.

Now all is well. I live in an old building (from the 17th century) and is entirely built in wood (it is a wooden floor but you can call it wooden floor). The parquet (strips of 10 cm) rests on a screed made on a wooden slab which in turn rests on huge wooden beams (30x40 cm). Above and below are other apartments.
My solution was the one you see below the speakers (double aluminum plate isolated from each other)

Good for you that for solving the problem with the D40, I did consider buying the D48 last year but was afraid that they are too much for my limited space so bought the D30RS instead and I am very happy with them. very tight and control bass .

That's good news!You were right about the structure of the floor being the problem.I live in an old house too,but not that old!I learned a lot from this thread.