Does a sub need to be on the floor?

No but that’s where most are designed to be to work best.

You can place a sub on an Auralex Subdude platform or something similar to help isolate the sub from interacting with the floor. That usually results in cleaning up the sound with more articulation to the bass (ie better sound overall as a result). Many with neighbors below in particular use these.

Adding subs is the best thing you can do for your system. 

with a decent active crossover integration is easy. But an 8" sub probably will not go low enough. Get a bigger one and turn it down as needed. 

As as for your orginal question moving a sub off the ground and putting it on a stand will help the tone in a good way. Just like moving your speakers away from the walls. As always two are better then one

james63356 posts08-15-2016 1:59pmAdding subs is the best thing you can do for your system.

Yep 
I get nourished with Firehouse 12" premium roast beef sometimes when listening to tunes.

+1 mapman

Short answer, the best position for a sub is how it loads the particular room it’s in. I have done experiments with raising and lowering a REL Strata lll in the front corner and the best position for bass articulation, extension and soundstaging was positioned in the middle with the driver facing the ceiling. I used the Strata lll as it is easy to move around and lift but the results speak for themselves.

Of course, this looks very odd and also needs a solid platform to perform best but it did teach me about how subs load a room. My current sub which is a REL Stadium lll works best sitting in the front corner, driver facing down with port positioned outward. I tried it with the driver facing the ceiling and the port positioned next to the wall and the results were impressive with regards to extension but integration with the main speakers was problematic.

It always pays to play with positioning in one’s own system despite what conventional wisdom dictates.