You can go to a variety of quality audio component rack companies websites and they will show pictures of their racks, with spikes, sitting on a hard material coupler over a hardwood floor. The point is, the spikes are meant to directly interface with the flooring surface. This provides a mechanical ground for the rack and the audio components within it to drain vibration away and into the hard surface on which it is resting. The same function for the equipment rack is also a function for speakers. Felt would interfere with this premise. The coupler, being a hard material and with a center detent for the spike, won't allow the spikes to damage the floor. However, it still is not something that should be dragged across the nice wood floor. Ideally, you would want to locate the speaker to its' best sounding position (carefully, maybe using felt pads only for this purpose) and then remove the felt pads and place the hard couplers under the spikes. Another method is to remove the spikes altogether and replace them with a vibration control footer that does not have a hard spike at all. For instance, the IsoAcoustics GAIA products. They have a nice video tutorial that demonstrates how to install the footers for speakers that reside on hard wood floors. They are well reviewed and nearly everyone who uses them praises them highly.
Best to you. Be safe and be healthy.
