elevating subwoofer...

Studs. Various automotive parts, and even home bits are double ended threaded rods.
Find some the right length, sharpen one end with a cutting wheel or such.. Or which have a rounded tip at one end.
Find studs which fits your screw in lost parts. Then add a nut. Screw in the threaded rod, tighten the nut with the pointed end sticking out.
Your spikes are replaced.

Yes large steel balls would dissipate energy. Can you find them easily?

It is easy to find replacement spikes; buy a couple of bolts and check the thread and then buy the spikes. Parts Express or other suppliers will have them.

Your factory spikes are likely either M6 or 1/4-20 threaded. Go down to Home Depot and buy a bag of each thread, see which one works with your inserts. Then buy some replacement from any of the many places around, like Parts Express ...

Why do you need spikes for a sub? Unless it's downfiring of course.

Put it on a Auralex Subdude.............you will dig it.....