Another inexpensive alternative is to take one of your spikes to the local hardware store and purchase hex bolts or carriage type bolts with same thread dimensions. You can then attach a protective pad if desired. These can be securely fastened to the speakers with the provided nuts. If nuts aren't provided you can purchase them at hardware store. Total cost should be less than $10.
This has worked well for me and my wood floors. I've suggested this several times and am curious if anyone has tried it.