@mojo771 I'm always fascinated by this topic because i also have my speakers on carpet over concrete. My speakers came with spikes and i do not use them, principally b/c i know that my housing pad (and the area i live generally) is very hard soil that carries vibrations a long way. i can sit on my flagstone patio and feel the vibrations from passing trains that are more than 5 miles away! So i assumed if i coupled my speakers to the concrete i would be transmitting those vibrations into my speakers. At present i don't use anything under my speakers but have been considering acoustic isolation devices and am grateful for this thread and the many who have recommended various products which i'll investigate. W/ respect to the article @sargonicuse provided i intuitively agree with the author's points but note that the author also works for (or did work for) AV Room Service Ltd whose products are designed for isolation/decoupling, so naturally he is against spikes. i found this article more convincing on the topic, not b/c of the spikes argument but because Jim Smith (RIP) was a highly respected voicer of systems and his argument is that speaker placement will affect the sound far more than coupling/decoupling--but in general he seems to argue against spikes unless they have an appropriate interface with the floor that [decouples?] them. FWIW.
https://www.psaudio.com/blogs/copper/spiking-your-speakers-whats-the-point?srsltid=AfmBOooli76fyTL8CjTXiZAz6CaVUwHte3tcUjgGZfgI5aL_EfyyAkxo#:~:text=Quite%20simply%2C%20using%20spikes%20as,that%20the%20bass%20is%20tighter. if the link doesn't work just Google "Spiking Your Speakers-What's the Point and you will see Jim's article as published by PS Audio.