Andy wrote:
I have 4 speakers in my apartment.

I would like to minimize the vibration transmitted to the floor.

Right now, they are sitting on towels.

Look for those "on the cheap" ideas. :-)

Well they do sell isolation cones (spikes) for just this purpose, but like
many things audio they are a lot more expensive than they are worth
(especially if you buy the ones with oxygen free metal).

For on the cheap, though, maybe make your own with some bolts and nuts?

Jon