I would never stack speakers on top of subs!! Way too many vibrations going both ways. If space is limited put the subs next to the speakers or stuffed in the corner of the room. Put them next to a couch or chair and stick a lamp and a plant or some coffee table books on the subs. Blocky end tables.
Stacking
Greeting, I have a set of LaScala ll looking into horn loaded subs as in the Tuba 24. I'm limited for space, so will it have a negative effect if I stack the LaScalas on top of the sub?