Not an audiophile but figured this was a good place to ask. I have a small subwoofer that came with my speaker set (Logitech Z407) and would like to use it for my Xbox audio since my monitor doesn’t have built in speakers. I live in a pretty old apartment and sound travels pretty easily between floors so I’m a bit worried my downstairs neighbor might hear the vibrations from the sub. I’ll be mostly playing games from the speakers at a relatively low volume (~30% max). Am i good to go or should i stick with headphones?
The best you can do is put a stiff slab (spread load and reduce deflection of floor) and a soft spring (passive isolation but only if soft with the sub bouncing on it a few Hz) under the subwoofer. A possible zero cost test would be a paving slab and some inner tubes if you have them to hand. This should substantially reduce the direct structure-borne sound which is often a significant component. The indirect structure-borne sound from the sound in the air of the room driving the walls and floor is not something that can be addressed. The air-borne sound out one of your windows and in a neighbours window can sometimes be addressed. Air-borne sound through ducting can sometimes be an issue in some buildings.
My experience has been that listening to music at standard levels in an apartment will upset the neighbours. That includes me hearing the neighbours music/noise. Listening to music quietly at TV/radio levels in the living room is usually accepted but not necessarily in other rooms such as those next to a neighbours bedroom. As you say, headphones are the usual solution for listening to music at standard levels in an apartment.