Not sure how the whole spike thing got started and why people like them. When using four, no matter what I did to create even support would eventually end up with a rocking motion where one spike would no longer be in contact with the floor to the same degree as the others. Using three is a solution but IMO does not result in as stable a platform, if there is any risk the speaker may be bumped. I believe McCormack was an early proponent with his tiptoes and then of course Audiopoints became hugely popular, and Mapleshade or edenSound brass footers, followed by a whole bevy of spikes and cones. However, none of those serve to isolate vibrations, even on concrete slab floors.
Vibrations are most typically isolated by some sort of spring and damping mechanism tuned to a specific weight range. Think about the springs and shock absorbers in your car’s suspension, or similar types of isolators used for machines, or even buildings.
Vibration isolation can often be modeled as springs and dashpots sort of like the closers on old-time screen door. The company I worked for once designed vibration isolation for an elevated seating section of an historic theatre that had begun hosting rock and gospel concerts where people would jump and stomp in unison causing potential structural damage. The solution used springs and dashpots.
Air bladders can also work well but have generally been problematic in operation - they always seem to leak. You could also look at EVPs by A/V RoomService Ltd. which seem to have a strong following. The primary isolation appears to come from an "air spring" resulting from Owens Corning 703 or 705 one-inch thick rigid fiberglass board, which is then faced with #4 brushed Stainless Steel sheet and either felt or rubber.
I certainly understand how Townshend’s spring solutions gain so many positive reviews. You can do basically the same thing using individual springs with damping, and particularly in my case where I already have Sound Anchors stands that provide a solid base extending beyond the dimensions of my speakers. Another lower cost alternative that many like is the Nobsound spring footers, or similar, which adjust to the weight of the speaker, although those do not appear to provide damping.
I believe Gaia uses an elastomeric material to dampen vibrations inside of their footers and a mechanical orientation to limit movement in certain directions. They have some interesting information posted on their website. Elastomers are sort of like damped springs in that they are inherently damped by the material itself and the spring constant is related to the durometer value, or hardness. Not all elastomers seem to work as effectively for things like speaker isolation. For example, most do not support the use of rubber, but platinum silicone and sorbothane both seem to be commonly accepted. Herbie’s Audio Lab offers a couple of different proprietary materials for their footer solutions. I switched from spikes, to Audiopoints, to Herbie’s products, to springs, and then to platinum silicone hemispheres (linked in my earlier post), which are able to economically achieve a damped spring type support that is suitable for a wide range of speaker weights.
Use what works for you and your budget, but the measurements seem to show the appropriate lossy solutions (i.e., springs and/or elastomers) being superior to spikes/cones, like these from Credo Audio.