Impact of speaker stands?

Although the height is where you want it, the foundation your speakers rest on isn't inert enough in my opinion. Isolation can't be achieved by use of foam and speakers to the degree necessary to isolate your speakers, not to mention the coupling needed.

From what I understand, the base should be firm enough as to not allow vibrations to travel up to the speakers and the speakers should be coupled to the base in such a way as to add another degree of isolation and to help drain vibrations from the speaker itself.

Foam and speakers just won't cut it. Microscopic though it may be, the amount of vibration that foam and speakers allow should be enough to smear or veil the sound to a degree that should be detectable in comparison to a really inert stand.

All of this will sound fanatical, but that's what this hobby is about. :-)

All the best,
Nonoise

The drivers in the JBLs will be contributing something to the mix just from the fact that active speakers are on top of them...so there's that...also I've found that small-ish conventionally stand mounted speakers have a "singing" pleasant quality if there is less stuff to couple with around them. There is some discussion regarding "spikes vs. rubber feet" where the rubber might be winning in many cases...I put Vibrapods under my skinny Silverline Preludes and they sound better than they did with spikes...go figure. Some high end speakers are being sold with some sort of "decoupling" feet these days...fanatical indeed.

Factors to consider are height ability to tilt if needed and if stands couple to floor or isolate.

I have dynaudio stands that couple to floor that work best on a more solid foundation and isoacoustics brand stands that sit lower to reinforce bass and also decouple from the floor which helps keep bass clean on less rigid suspended plywood floors on upper levels. They also provide option to tilt up which helps with lower placement.

I also put my ohm 100s on auralex sub dude platforms to isolate those from unwanted floor interaction on the same upper level. Not needed in finished basement where floor is thin dense carpet and pad over concrete foundation.

Stands are a must, as your set up now does not isolate the speakers and no matter what padding you use, it will be truly isolate them. Best to find stands that you can spike on where they meet the floor and also spike them where the speakers meet the stands. Yes, it is called a 'double spike'. Don't use blu tack or moon gel. Enjoy.

There are many articles on the internet about the speakers stands (use Google). There is also the litrerature dealing with this subject, for example Jim Smith: Get Better Sound. However, the stands must be rigid and must damp the vibrations as much as possible. Considering the height of the stands, there is "golden rule" - the tweeters should be as high as the the listener ears. I think, the placement of your Kefs on stands would be better solution.