Does a Subwoofer Make Spiking Redundant?

My speakers are spiked, heavy carpet, pad and plywood underneath.
   If I place on rug, they are tipsy.

The job of the spikes is to pierce the carpet. Lose the plywood and pad.  But you may leave a mark on the underlay if it is hardwood.

OP misunderstands the reason for spiking. It is to prevent the whole speaker moving around and adding that movement to the signal driven movement of the cones etc.

right. A different way of phrasing what i wrote above.  It is modulation.

When I put spikes under my speakers I could definitely hear a marked difference. If a blindfolded person could not hear the difference then I think it would be more a matter of The Emperor's Cloth Ears. The thing was, I wasn't really sure at the time that the difference was an improvement. Getting the spikes in the puckies I was putting the tips of the spikes into was such a nuisance, me working alone and all, I didn't want to go through the trouble of removing the spikes only to find I liked it better spiked and have to do it again. I might give it a try, but I wouldn't want to do it before the subwoofer burned in. I'm not the sort of person who runs his gear hour after hour to get it burned in - I live in an apartment. (In fact, when I watched a move - Many Saints of Newark, as it happened - the movie soundtrack bass was so thumpy that I might have to turn the subwoofer off when watching moves.) So I will let the subwoofer to burn in the course of nature. I did the same thing with my front speakers - at first I was a bit underwhelmed, but a month or so afterward I started to become aware of how much better they sounded.

Clearthinker— Mc is always wrong. Instead of asking questions about the floor, the speaker, or is a sub, he just blurts out garbage.

It all depends on the flooring and what does the speaker manufacturer recommends. For Tekton speakers, springs or spikes won’t make any difference, but ask Magico what they recommend and you will get the m-pod choice which works great for their speakers. Same goes for Wilson and others. Me, I would look at Isoacoustic pods for the speakers if on a plywood/joist floor or spikes on a carpet/concrete floor