Use Harmonix footers under the spikes. They are expensive but actually improve the sound (at least in my case it did, tightening bass and adding some needed warmth).
How to stabilize speakers without spikes.
My wife won! In the interest of domestic tranquility I have relented. After living with carpet over wood floors and spikes on my speakers for many years, my wife wants to have a wood floor (maybe tile) installed in our house. I've always used spikes in my Vandersteens (2Ci) to stabilize them with a slight front tilt upward. What would you pros do now? As always, thanks for sharing your knowledge.
Tom
Tom