First off, I realize my question goes a bit beyond the usual scope of this forum and is only loosely related to Project Cars...I'm posting here in hopes of finding some people who have a similar setup to mine and maybe have some experience with solving my problem. If the moderators think this post is too far off-topic, just kindly close this thread, and I will look elsewhere

I have recently added bass shakers to my rig and am really enjoying the added immersion, but quickly had to realize that my downstairs neighbours don't exactly share my enthusiasm. I chose the relatively cheap but still very effective route of mounting six Sinuslive bass pumps to my Playseat and driving them with the Simracingcentral software. My rig is shaking and vibrating to a satisfying degree, and I've decoupled it from the floor with a set of G44 rubber feet so the floor doesn't carry the vibrations, but the problem is that the bass pumps of course are subwoofers and emit low-frequency sound, which of course carries very well through the floor. The biggest problem is that two of my bass pumps (the one under the pedals and the one under the seat) are essentially pointing straight downward, which (as I've realized too late) is a surefire way of annoying the downstairs neighbours.

I can't think of any other way of mounting these two speakers, and even if I could figure out a way of having them not point downward, I'd just transfer the problem to the upstairs neighbours instead. So...since I don't need/want any sound to come from them at all and only need the vibrations, is there a cheap and easy way to sound-proof the things by covering them with some sort of dampening materials? Would bitumen mats work? Even if it is possible to silence them, would I run into overheating problems/potential fire hazards by completely covering them with some suitably soundproof material? I notice they get pretty warm after an hour or so. Or am I essentially stuck with an unusable tactile feedback system than has to remain turned off unless I move to a ground floor apartment or alternatively maybe get more noise-tolerant downstairs neighbours?

Since the Sinuslive speakers are essentially a poor man's solution and were dirt cheap, I'd be willing to replace them and install something else if absolutely necessary. Are there any affordable tactile transducers on the market that are either sound-proofed by design or use another method of generating vibrations? From what I've read, the original Buttkickers might potentially solve my problem, but they are so much more expensive than the Sinuslive bass pumps that I'm a bit wary of spending loads of money on something that might leave me with the same problem.

Thanks for any and all input! Not just from me, but I'm sure from my neighbours as well :P