Speakers and subwoofers like to be solidly mounted to add structure to the enclosure, they do not like to be in micro motion.
The ONLY reason you would ever want to iso mount a speaker or subwoofer is if the energy of the speaker is transfering into something such that it is audibly resonating, e.g. a suspended wood floor.
In that case you would introduce isolstion of some sort because not using it is worse than using isolation.
isolation is a compromise solution, the speaker is now in micromotion. no isolation is always best if the speaker isnt causing something else to vibrate audibly.
The ONLY reason you would ever want to iso mount a speaker or subwoofer is if the energy of the speaker is transfering into something such that it is audibly resonating, e.g. a suspended wood floor.
In that case you would introduce isolstion of some sort because not using it is worse than using isolation.
isolation is a compromise solution, the speaker is now in micromotion. no isolation is always best if the speaker isnt causing something else to vibrate audibly.