If you walked up to one of your 80s and pushed it, would it start swinging, or are they attached in solid way that prevents that? If they do swing, you run the risk of losing some accuracy. Allow me to explain my theory.
Because every action has an equal and opposite reaction, when your driver cones move forward, your speaker cabinet will move backward, trying to keep the center of mass of the entire speaker in the same place. Likewise, when the driver cones move inward, the speaker cabinet will move forward. Because the speaker cabinet has much more mass than the drivers, you can't really see this happening. The effect would be a subtle muffling of soundwaves.
It's always a good idea to have the speakers anchored as rigidly as possible.
I fully admit that the motion of the speaker cabinets themselves might be small enough that it's virtually non-existent, so this may be a complete non-issue.
