Bloated speakers/weight wise

My speakers are 50 inches tall and weigh in around 70 lbs. There is a 10.5 inch fullrange driver at the very top of the column firing forward. They sit on a plinth that is 12 inches square with a spike in each corner. They do not resonate. The box doesn't talk or rock. They play very loud. They are 101 db efficient. They seem to contradict much of what has been written here. I think the stability issue may be due to the fact that my driver cannot be seen to move, even at loud volumes because the excursion is very short. It seems logical to me that less pistonic excursion would be less apt to cause the box to move. As for resonance control, I don't know how they do it but there does not seem to be any cabinet activity at all.
All this leads me to conclude that mass is a substitute (and not necessarily an effective one)for innovative engineering.

Aha! Onhwy61 has offered a good explanation as to the workings of my speaker. They have a downward firing bass tunnel running the full height of the cabinet and the size of the aperture facing the floor is quite large. The freedom of the backwave to escape and the direction it goes would perhaps explain why the cabinet neither rocks nor vibrates.
My first post was written before his explanation appeared.

Macrojack, my explanation applies to both sealed and non-sealed speakers. A port, if appropriately designed, offers a controlled path for pressure to escape the speaker cabinet. Ported speakers still have to address cabinet flex. If I got it right, doesn't your speaker have a very slick multi-layer cabinet design. And since when did 70 lbs. become a light weight speaker?

Hwy-

I think you are correct about the cabinet but I am not sure.
I think 70 lbs. is light in comparison to the behemoths being mentioned here. And the things are over 4 feet tall besides.

The aperture at the bottom is about 4 inches by 9 inches. I don't know how it is configured inside but I would imagine an opening that large would present little resistance and therefore minimal pressure. Is that correct?

Macrojack, How do you know that your cabinet does not produce any sound? How did you test for this?

After reading some of this thread I did a little experimenting. First I tried to feel vibration on the cabinet with my fingers and could not feel any, so I tried my lips and then my check (the one on my face), still nothing. Next I held a glass up against the cabinet, (you know, like holding a glass up to a door as to hear what is being said on the other side of the closed door), then I could hear something coming through the cabinet. But what worked even better is just to press your ear firmly up against the cabinet, by doing this I could hear even more. Don't forget to plug the other ear and cut the volume off on the other speaker.

Have you tried that? If not, how did you test?