Originally Posted by Bond 007
Or...If you dont have the test equipment or the know how to use it or the tools or the money and time to find the materials you could just remove EVERYTHING from the room.
It's not hard to track down vibration. First off, small objects don't vibrate. The wavelengths from a sub run from about ten to forty feet long, and anything that's less than a quarter-wavelength or so in dimension won't be vibrated, as the wave simply goes around it (see principles of diffraction). So what vibrates are large surfaces: floors, walls, ceilings. You don't notice them vibrating, or hear them vibrating. What you do hear vibrating are objects connected to them, pictures, shelves, etc., and other objects sitting on said shelves. In the OPs case the baseboard itself isn't the issue, the wall behind it is. He doesn't hear the wall vibrating, he hears the baseboard vibrating in response to the wall vibration.
If you have objects vibrating the cure isn't to isolate the sub, as that doesn't stop those ten to forty foot long wavelengths from vibrating the floor and walls. It's to either secure or isolate the objects. Shelves full of brick-a-brack in a HT aren't a good idea, but if you must have them get self-stick felt pads to put under them.