What is a good base for speakers

One idea: (from ASC website)
(tube trap)

“If you just buy a couple of these and stick your speakers on top of them, it will completely transform the sound of your bedroom, I promise you." Pete Townshend
the Who

 And to add to this-two more above / on top of the speakers ... 

What you need is to keep the speakers from moving in the direction of what the drivers are moving, so that the drivers can push air without the cabinet fighting it. I believe the ADS are front firing drivers, which means you need to keep the cabinets to be kept still in the fore-aft direction, mainly. Of course it's better to eliminate motion in all directions. 

As for carpet below the stands, its best to increase mass at the base of the stands, and use something with spikes (below the stand) that penetrate the carpet and padding to mechanically couple the stand directly to the floor (wood or concrete). This hopefully eliminates the carpet/pad spring that otherwise allows the speaker to bounce or rock.

After that, you can consider stiffening the stands so it doesn't bend.

just buy modern stands with bottom spikes

I use Deer Creek Audio steel speaker stands like these:
https://deercreekaudio.com/t/steel-speaker-stands

The focus, stability and exactness of images is top notch, despite the fact the speakers rest on felt pads affixed to areas of the steel base.

All the best,
Nonoise

On a concrete carpeted basement, springs (like Nobsound) would work better than spike, rubber (or silicone) cone/feet, granite, concrete slab, ...?
Nobsound springs (4 of them) support up to 40lbs, but I guess it is pretty limited. Most full range speakers will weigh more than 40 lbs.
I’ve never tried springs. I thought spikes work best. I might try springs on my subwoofer. It rattles too much on high volume.

[EDIT] I see that it supports up to 66 lbs (or 30 kgs). The would cover most mid size speakers.