What your choice speakers with spikes or speakers with a vibration isolation device?

I always decouple, no matter the floor..No spikes ever...I dampen the enclosure, as much I can. If you can get the KNOCH factor to green concrete, you've done a good job...

I go by the pound..about 60 lb a foot for monitors, bass lowriders or bass columns.

I'd hang the darn things if I could figure a way without turning the room into looking like the Big Top at Barnum and Bailey's..

@ 60 lb a foot, that's over a ton hanging from the rafters, with just 4, columns. There are 8 enclosures in there.

Hanging is out, spikes are out. 

Adjustable spring mounts and silicone.
A spring suspension and different viscous ratings for the rubber, from staying liquid (like an accumulator, or a shock), to a VERY hard dry material.
Hospital generators, and power plants in floating structures use them.. Where I got the idea from 40 years ago. ZERO harmonics, as long as the dampeners would stay charged, (no leaks from the bladders) with nitrogen

There is NOT a better way to control harmonics...

Vibration = distortion, simple...

Regards

I suspended my Rogers LS35a speakers from eye 👁 hooks in the ceiling with bungee cords. Was that so wrong?

Geoffcait, I don’t have enough scientific chops to say either way. I would think that if the bungee cords still had some spring affect in them then it would be the same or better than a spring loaded solution on the floor. I have been fascinated with the line array speakers that you see at commercial venues. They make sense there I wonder if that idea will creep in to the home audio market. I guess somebody is going to have to figure out how to make it lookLast commercial and more homey

Yes, bungee cords act like springs. Same idea whether the springs are compression type or the tension type. 

The best choice would depend upon the speakers used, the floor/substructure composition and (of course) your ears/preference.

List your gear/room/floor info in order to receive informed/meaningful opinions.

DeKay