Speaker spikes-worse sound-what gives?

As Pmkalby points out, never is there an always. Your experience mirrors mine exactly, and from the reading I've done here and on Audioasylum, a fair number of people with floorstanders on suspended floors. Spiking the speaker to such a floor, as opposed to decoupling it, results in a significant degradation of the sound in my opinion. With the speaker spiked to such a floor, you can actually place your hand on top of it while playing and feel a ton of "vibration", for lack of a better word, that simply is not there with the speaker decoupled from the floor with something like vibrapods. And the sound with spikes, as you noted, can be pretty grim. It's as though all the flow and life has been sucked out of the music, with the bass being thinned out, the midrange being pushed forward and the highs being overly emphasized. You will probably have many suggestions here with respect to placing concrete pavers, or granite slabs, etc. under the speaker and then spiking the speaker to those. That may work as well, but what I like about the approach I've outlined above is that the laminated glass is 1) very thin so that it does not raise the speaker and the drivers into a very high position that may do more harm than good 2) it is, because of its construction quite inert and acoustically dead and 3) it is cosmetically unobtrusive.

I am currently using vibrapods between the glass and the speakers, but am tempted to try the Herbie's product because of very good performance from another one of his products. It may be worthwile to go with some other type of footer as well, but what I've described is fairly inexpensive and sounds quite good. I'm pretty cheap.

Yea, spiking a speaker couples it to the floor pretty effectively. Whether it's a good idea depends on what you're coupling it to, though. If you're spiking it to something solid, then it will help to stabilize the whole enclosure and can improve the sound by, in my layman's understanding, effectively adding to the inert mass of the enclosure. If, however, you couple to enclosure to a less inert surface (such as a suspended, wooden floor), you are really only expanding the resonating surfaces that can muddy or otherwise affect the sound. Spiking a speaker to a less-than-solid and inert surface is always a crap shoot. Pretty simple to diagnose, though -- if it doesn't sound right, it's probably not a great idea.

There seem to be two basic approaches when straight spiking doesn't work out. You could either seek to decouple the speaker from the uncooperative floor (air bladders, vibra pods, various flavors of isolation shelving, and countless other products or homebrews) or put something solid and massive under the speaker and couple it to that (ye old slab of granite, e.g.). Then, of course, you could always mix and match the two, such as when you hear about folks putting a slab of concrete on a bicycle innertube and then putting the speaker on that. Folks'll argue over what works best but, depending on their gear and circumstances, they're probably all right. I sincerely doubt there's any single cure-all, but I'm sure, in any case, that spikes aint it. Assuming you think it's fun to try new stuff, then anything that sounds like it's worth a go probably is. Have fun and best of luck.

Thanks everybody. I have taken off the spikes and may try some of your suggestions. Keep the ideas coming.

Same worse bass response with spikes on base of 30" metal stands with two way monitors. Low cut pile carpet over a hard floor. Lost the deep bass with spikes attached. Sounded best with them removed and metal bases sunk into the carpet worked just fine. Though the speakers move some when playing loud, the bass response gained outweighs the unneeded anchoring the spikes give. Again, the ears are the judge here and not the theory.

It is possible that the additional height that the speaker is raised off the floor by the spikes may have reduced the bass reinforcement that is normally provided by the floor. This could have reduced the bass frequencies by 3db due to the radiation into 1/2 space, instead of 3/4 space. Placing a small plate over the open space between the bottom of the speaker and the floor may restore that boundary reinforcement, and thus the bass response. It is worth a try.

The spikes generally cause the speaker to be more steady, and improves sound by reducing doppler that is caused by minor speaker rocking on an unsteady base. They can also provide a vibration evacuation path. But if the floor is very unsteady, then this may be a problem.

I agree that some experimentation is in order to find the best result in you situation. I think it is easy to place a temporary plate over the gap between floor and speaker that is created by the spikes raising the speakers off the floor. It just might do the trick for you. Boundary reinforcement is a real effect, and it can be compromised by even a couple of inches gap.