How much space between cables is enough?

Interesting, I wonder what effect suspending cables from weak springs or 'floating" them on 6" inner tubes would have.

Try it and let us know.

Tony, I suggest that you stick with the physics until you have 6 figures invested. Physics suggests that putting anything ferromagnetic, like a spring, close to a signal line is a bad idea.

Because it tends to attenuate the high frequencies.

Where are the rubber bands?

Researching the idea of suspending cables I came across a post on another site about using rebar chairs for this.  They come in different sizes and look like they would enable the rubber band trick.  Cheap hack if you think it would work.  Personally I doubt I could hear the difference but if I ever get things settled down enough that I'm not always moving stuff around I might give it a try. 

https://www.homedepot.com/p/Hercules-3-in-Rebar-Chair-100-Pack-912/204220121

And rather than buying incredibly expensive audiophile vibration isolation gadgets I would love to know why these guys wouldn't work almost as well:

https://www.supplyhouse.com/sh/control/product/~product_id=MP-3E