Down-firing subs and downstairs neighbors

Hello Audiogoners,

I am looking at subwoofers for 2 channel music. I will soon be moving into the 2nd floor of an older wooden house, with neighbors below me. I don’t want to drive my new neighbors crazy.

It seems intuitive that a downward-firing sub would penetrate the floor more than a forward-firing one--but is that true? Also, can you do things to mitigate, like put a down-firing sub on a piece of stone, or a particular material?

Any suggestions/info much appreciated