Does a Subwoofer Make Spiking Redundant?

Then mids will still cause vibration. The type of food the speakers are on matter too. Carpet over concrete or wood etc. 

What you are trying to do is fix a small mass to a much larger one to drain away excess vibrational energy, to dampen resonance. It is the exact same principle you use when you fix a cartridge to a tonearm. Ideally you would bolt the speakers to the floor and I have seen people do this. The problem is the mass of your house is not solid. It vibrates also. Here a concrete floor is also a big plus but an option many of us do not have. After bolts spikes are the next best thing. Both subwoofers and main speakers should be fixed although it is more important for subwoofers. Putting speakers on isolation springs is an odd thing to do for two reasons. This allows the speaker to vibrate itself silly and the floor is going to vibrate just the same from the acoustic energy released by the speakers. So, if you want the ultimate, bolt your speakers to a concrete floor.

Unless your floor is concrete, I would think isolating your subwoofer would be better. With standard wood frame construction, you don’t want the sub to couple to the floor which then acts like a radiator vibrating at its resonance frequency, mucking up sound quality. When I isolated my subwoofer from the floor, sound quality went way up. I noticed that it didn’t interact with the room as much - much less vibration coming thru the floor. If your goal was maximum loudness and impact, maybe you want that effect, but you don’t where sound quality is the objective.

Always decouple, everything. You cannot be heavy enough or secure enough. The problem is timing. The floor, weather wood concrete or whatever folks use can’t isolate vibration unless it’s thick rubber, THICK rubber like the Kursk 3" thick.... Most people don’t have that type of isolation. 10-12" thick concrete will work. 3.5 or 5.5" is not thick enough unless it’s on friction piers. That is an expensive slab...

It’s better to use air bags, spring or pods. The better isolation you can afford the less the timing issues. Smearing is a PITA until you get rid of it.. Like magic!

Clean up the huge passive bass radiator from the floor walls and ceiling. Treat the standing wave issues in the room, you’re sittin’ in TALL cotton (as my Mom use to say) I use heavy curtains and two pocket doors that slide open on the back wall in one room. My ears don’t like to much pressure. OB servo subs really help. I use to use inner tubes on 2 12cf bass bins and set the feet in a pocket of 4" memory foam, 95% isolation.

On spikes they would have drilled holes in that 41/4" 80 year old concrete floor, close to 300 lb each.

I have a pair right now 250lb (12cf) with no driver holes yet. A pair of 21" Daytons, would act like pile drivers on spikes. Turn up the bass and it would leave concrete dust on the floor.. LOL

Regards

" bolt your speakers to a concrete floor" - this is completely wrong.

The whole purpose in "decoupling" the speakers, and sub, from the floor is to minimize, or eliminate, the vibration from reflecting back into the speaker. This reflecting vibration muddies up the sound of your speakers. Eliminating the reflecting vibrations tightens up your bass, and the speakers’ sound becomes more clearer. Bolting the speakers to the floor will only insure that the vibration passes from the speaker into the floor, and reflecting back into the speaker cabinets.
Spiking the speakers will only minimize this vibration. The best ways are to use springs, as suggested, seismic podiums, or energy dissipating pucks.