"D.M. Procida" wrote in
message
...

Would speaker spikes help cut down the sound transmitted to the
occupants of a flat on the floor below?

No. The vast majority of the sound transmitted to the occupants of a flat
on the floor below is first transmitted via the air in the room.

If not, what would?

Using headphones or turning down the sound.

Isolating your entire listening room from the rest of the building.

Seriously.