If I recall correctly, Alan at Axiom has stated that using spikes, rubber, or nothing makes no difference in the sound. The spikes are intended for carpeting to secure the speaker. What makes a difference is positioning of the sub in the room, and what other furniture/carpeting/wall coverings you have. If you have concrete floors, your sound will definately be different. Heck, maybe the sound is coming from the spikes moving around during heavy activity.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85