How much space between cables is enough?

+1 @rodman99999 

Power cables can run in parallel, closely, and should cross everything at 90 degrees. If you must coil power cables, do it far from everything else, and make the circles as big as possible.

Speaker cables should cross interconnects at 90 degrees.

Interconnects can run in parallel, closely, if they are shielded, like co-ax.

Closely ~ 1".  More than that is diminishing returns, IMO.

@millercarbon

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

+1 @terry9 

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.