Yeah, you're really not going to be able to solve this, other than balancing the sub out properly in the first place. Basiclally, down-firing, front-firing, slab, no slab, or even suspending the sub in mid air for that matter, isn't going to do anything about the airpressure and bassmodes in your room from being excited!!! Basically, unless you do something to your floor, it's going to respond accordingly. That's how bass works.
conversly, people think if they move their sub out from the walls, that it won't be as boomy in the room next to it. WRONG!!! That's not how it works.
Acoustics are what they are. You'd need to, like I say, just make sure you're sub is balanced out in level with your mains/the rest of the system (other than sub being way louder than the mains), and add some mass to your floor!
Good luck
conversly, people think if they move their sub out from the walls, that it won't be as boomy in the room next to it. WRONG!!! That's not how it works.
Acoustics are what they are. You'd need to, like I say, just make sure you're sub is balanced out in level with your mains/the rest of the system (other than sub being way louder than the mains), and add some mass to your floor!
Good luck