All you need is a decoupling device. The DIY "handball" and "stress ball" solutions are fine and inexpensive. Anything that is squishy enough to absorb vibrations, but not so squishy that it can be completely compressed by the weight of the turntable, and not so stiff that it doesn't act as a good shock absorber.
If you don't care too much about the price and you're fine with spending $25-$50, you can go for
IsoNodes (You'd want the "Large" size for a turntable) which are definitely over-priced, but are effective and $25, so the over-pricing isn't the end of the world or anything
You could also go for an
Auralex SubDude Isolation Riser for $50, which, again, you could build or substitue something else for cheaper, but at $50, also isn't the end of the world if the lowest price isn't your #1 priority.
Auralex also has the
SubDude HD which is the same thing dressed up a little in velour rather than industrial carpet.
And if your turntable's feet are farther apart than will fit nicely on the 15" x 15" Subdude, there are the larger
Auralex GRAMMA and
Great GRAMMA
What I would highly suggest is that you not just decouple your turntable, but also decouple your subwoofers. The SubDude, GRAMMA and Great GRAMMA are the perfect choice for decoupling any subwoofer. Just choose the size that will fit your sub. The SubDude is 15" x 15"; the GRAMMA is 15" x 23"; and the Great GRAMMA is 19" x 30".
When a standard subwoofer plays, it physically vibrates. You can easily feel this if you just put your hand on the top of the sub while it's playing. You'll easily feel it shaking. Those physical vibrations go directly into your floor - and regardless of the floor's material (wood, concrete, marble, what-have-you) the floor will vibrate in sympathy. There is no such thing as a completely inert floor!
With the floor vibrating, the floor is connected to the walls, which are connected to the ceilling. Sound vibrations travel VERY easily through any and all of these solid structures, with bass frequencies being the most powerful and easily transmitted. This is the reason why you can so often easily hear bass thumping away in other rooms of the house, even when the higher frequencies are muted. The bass frequencies are literally using the structure of your house to travel. Rather than being conducted via the air, they are now structure-borne transmissions.
So not only will decoupling your subwoofers from the floor help to alleviate your turntable problems, it will also reduce (not completely eliminate, since the structure will still actively vibrate at its resonant frequencies just from interaction with the sound waves that travel through the air and hit the walls, floor and ceiling), but it will reduce - noticeably - the "leaking" of bass into other rooms of the house.
It is my opinion that every subwoofer and tower speaker should be decoupled from the floor. There are instances (for example, when you have a very thick carpet pad) when the subwoofer or tower speaker is already decoupled. But by and large, decoupling helps in almost every situation and it NEVER hurts. At worst, you'd have spent around $50 for no real benefit, which sucks, but you can easily return a GRAMMA and get your money back
Also, contrary to what some publications state, using "spikes" or "feet" of any kind on the bottom of your subwoofer or tower speakers does NOT decouple them. It is the exact opposite! You are now exerting all of the downward force (the weight of the sub or speaker) into just four teeney tiny points! The downward force at each of those four tiny points is now MUCH greater than if the downward force were spread over the much, much larger surface area of the entire bottom of the sub or speaker. So "spikes" or "feet" only serve to
couple the sub or speaker even more greatly to the floor, not
decouple it. Any publication that states otherwise has it completely backward.
And if you want to ever take things to the next level, consider soundproofing construction for your room. The place to go, without question, for the best soundproofing info is
soundproofingcompany.com
Read their articles and library. And heck, give them a call on the phone. All they do is soundproofing and they're happy to talk with anyone who is interested. You'll learn all about decoupling and the other elements of soundproofing.
Hope this helps!
