mass loading speakers

Any speaker can be mass loaded. I put a BDR Shelf on top of my Moabs. Anything that adds mass is mass loading.  

Anything you put inside will not only add mass, it will also take up volume, which will change the resonant character of the speaker. Mass will also change the vibrational signature a bit. Mass is only one property of matter. There is also stiffness and damping factor. These three properties combine to give whatever sound change you hear.

I've done this stuff enough to know it does make a difference. How much difference, whether you think the difference is good or bad, all depends on what you want and how you do it.   

A much better approach, in terms of bigger/better results, is to put the speaker on springs, either cheap ones like Nobsound or expensive but really good ones like Townshend. 

guess I should have read the manual better as it said it was for the following speakers and the ones I am thinking of getting are not the Sky Tower.

Recommended for Arro, Sky Tower, Hawk and Forest

i saw the Nobsound that you mentioned and might be worth a try if I decide to get them.

Springs absolutely must be tuned to the load. The beauty of Nobsound, they can be adjusted to carry a wide range of loads simply by removing springs to get to the right sound you want. You can hear the sound change as you do this. Also they are dirt cheap, yet perform better than a lot of much more expensive stuff, and almost as good as some really expensive ones. They are nowhere near the same league as Townshend, but then they are nowhere near the price either! Truly the bargain solution and entry level to discovering spring isolation is the bomb for all components.