You can buy a device that adheres to the speaker cabinet and will tune out the cabinet resonances. Unfortunately I can't find the catalog where I saw it (MCM I thought). Spend 15 minutes looking and can't *&!#$@%# find it, sorry.
Vibra-pods under speakers will absorb resonances. But the speaker will not be solidly mounted and there could be problems with imaging.
Vibra-pods under speakers will absorb resonances. But the speaker will not be solidly mounted and there could be problems with imaging.