At the moment my living room floor is thin, stripped gappy floorboards that are acting as a great big drum under the sub. I figure i need to isolate it somehow and have done the searches on DIY and pro platforms and made a decision on what i'm going to try. However, one thing doesn't seem to be covered much that i would have thought was important - what should a downward firing sub fire against? In modern living rooms it could be anywhere between the two extremes of concrete or thick carpet on heavy underlay. I'd have thought this is going to make quite a difference to how the sound is dispersed - what should i be aiming for? At the moment it's looking like the sub will be on a smooth granite slab but that could easily be covered.