ShadyJ won't like what I'm about to say, because for some reason, he doesn't believe that putting vibrating objects on some sort of cushion will reduce the transmission of those vibrations into the surface on which the vibrating object is sitting.
But if you aren't crazy like ShadyJ is, you should be pretty familiar with the idea of putting some sort of cushion under a vibrating object in order to damp its vibrations
A great deal of the physical shaking in your neighbor's apartment is due to having the "feet" of the subwoofer in direct contact with your floor. Those "feet" on the bottom of the subwoofer make the transfer of the subwoofer's vibrations into the floor worse. It's all about pounds per square inch. The weight of the subwoofer doesn't change, but with the "feet" in place, you've got far fewer square inches of surface area in contact with the floor. End result is very high pounds per square inch. And all of the physical vibrations of the subwoofer get transmitted directly into the floor. The floor is connected to the walls. The walls are connected to the ceiling. So before you know it, those vibrations are quickly travelling throughout the entire structure of your apartment building!
While it won't solve ALL of your problems (there's still airborne sound to consider, of course
) having some sort of damping in between the bottom of your subwoofer and the floor will help. All you're after is a shock absorber. Stop the vibrations of the subwoofer from reaching the floor. I've no idea why, but ShadyJ swears this is "snake oil" and "BS". Meanwhile, every other person on Earth understands this idea pretty easily. I mean, put your phone on vibrate and sit it directly on a table top. Phone rings and the table buzzes like crazy. Put a pillow under the phone, and when it vibrates...WAY less noise, right? I've no idea why ShadyJ thinks that's "snake oil", but it seems pretty self-explanatory to me.
Now, I'm giving ShadyJ a hard time here, and I want to give him the benefit of the doubt. He's mostly just railed against "subwoofer platforms" or "decoupling risers", such as the Auralex GRAMMA. Those are the devices he's called "snake oil" and "BS".
Now, if his problem is simply that he thinks the $50 asking price is too high, I've no beef with that. The Auralex platforms are nothing more than a piece of MDF wrapped in carpet with some foam glued to the bottom. You can certainly build something very similar yourself for less money than $50. Or you could use something as simple as some blankets to act as a damper between the bottom of your subwoofer and the floor!
But ShadyJ has flat out said that he doesn't believe damping platforms do ANYTHING because he hasn't seen the objective measurements to prove it. And, apparently, having windows and picture frames shake and rattle when there is no damping platform in place vs. having those same windows and picture frames NOT shake and rattler - or at least shake and rattle much less - is not proof enough. We're all being fooled by the "snake oil" according to him. But I dunno. It's been pretty cut and dry for me. Window rattles when the sub's sitting directly on the floor. Window doesn't rattle when I have a damping platform under the subwoofer. And funny thing is, every single person who's ever been to my apartment experiences the exact same thing. I guess we're all delusional. Unless, of course, there were 3rd party measurements printed by someone other than me. Then we could believe what our senses of sight, hearing and touch tell us is obvious. But until then, according to ShadyJ, we can never know. Apparently the window and picture frames no longer rattling is all placebo effect. It's awfully strange that my cat jumps when the window rattles, but doesn't jump when the window doesn't rattle though. I guess he's subject to the placebo effect, too! Fascinating.
lol
Anyways, to be clear, I'm saying this light-heartedly. But I've gotta give ShadyJ a hard time about this. Calling the entire notion of damping vibrations "snake oil" just isn't something I can let slide by. It's just plain bad advice to tell people to NOT damp in between the bottom of their subwoofer and the floor when that is such an easy, cheap and effective solution to so many issues with bothering the neighbors or other people in different rooms of the house!
And I mean, here's the final word - it's a pretty darn easy and cheap experiment to try for yourself! Fold up a few thick blankets. Put them under your subwoofer. Play the subwoofer. And talk to your neighbor to see if there's any improvement! If there is, then great! You know that damping will help in your case, and you can make or buy something a little more visually attractive and physically stable than folded up blankets
If it doesn't help, then so what? Did it kill you? According to ShadyJ, you shouldn't even try. Apparently it will harm you in some way to perform this experiment for yourself. I don't get it...
Anywho, give damping a try. Heck, let's say ShadyJ is right. Let's say damping is all "snake oil" and "BS". Let's say it's all placebo effect. If your neighbor and you both stop hearing annoying rattles, and he stops complaining, and you can enjoy your subwoofer without bothering your neighbor, does it really matter? Seems like it would still be a solution to me!
But, of course, it isn't just placebo, and it isn't "snake oil" or "BS". We're all very familiar with how damping vibrations works. So that's all a product like the Auralex GRAMMA risers is - it's a damping platform - a way to stop the vibrations of the subwoofer from being transmitted into the floor. You can hate the price - that's totally up to you. But you can't hate the simple idea of damping. It's a pretty basic and well understood concept