I live in an apartment. There’s an occupied floor below me. I have the subwoofer in my sound system sitting on carpeting, which covers the concrete floor. I don’t run my system very loud, but I’m concerned that the low frequencies are being conducted by the concrete floor into the apartment below mine.
So my question is - if I put the subwoofer on those spiked feet you see in HiFi shops, will that reduce the transerence of low frequency energy, or increase it?
I’m thinking it might reduce it, as the size of the contact area will be significantly reduced, but it might increase it, as the points will no doubt go through the carpet and link my subby directly with the concrete floor (their concrete ceiling).
Any time a propagating wave hits a surface interface, some of the energy is reflected back into the original material. Putting it on spikes is going to create another surface interface for the waves to have to propagate past before it goes completely through the floor. However, practically, it’s not going to make a difference; the waves are going to be very close to their maximum, and will not attenuate noticeably different with an extra inch or two of air gap. I don’t even think a rubber mat will help, since the sound waves will be filling the room and going through the floor at other points that are not directly below your subs.
Is you sub floor-loaded or ported? A floor-loaded sub has the driver on the bottom of the cabinet and pointed straight at the floor. A lot of older models are built this way. These are tough to tame as the floor is part of the acoustic design. One thing you can try is to turn it on its side and make it a wall-loaded sub, but that’s only feasible if you’ve got an exterior wall. You really don’t want to do this with a shared plasterboard wall.
Ported designs don’t care nearly as much if they’re on a floor or on a shelf. You could try setting the sub on a piece of foam rubber such as a couch cushion. This will mechanically separate the sub from the floor, but will do nothing for bass notes in the air that make the floor resonate.
Frankly, the best thing to do is be neighborly. Go downstairs and say “Hi, I just got a new stereo system and just wanted to check that I wasn’t driving you nuts.” If they say "Oh, no, we haven’t heard your music at all, then you’re pretty much golden and blessed with a really inert building structure. On the other hand, they may say “What the hell are you listening to? It’s shaking the fillings out of my teeth!” in which case, you need to work harder on isolating the bass, turning down the bass, or negotiating schedules. eg: find out when they’re away so you can use the thing without fear of annoying them.