I read your posts very carefully. I object to marketing slogans like "structure instantly absorbs the energy generated from the drivers". What does this mean? You know that you do want to hear the energy generated from the front of the driver right? No to mention that Sounds_real_audio was talking about drivers back waves which is different subject all together form cabinet resonance control, which I assume is what you are talking about.
What you are describing is a typical way to build light, yet stiff structures. You get the stiffness all right but Last-a-foam is a very rigid material that will do very little, if anything, to damped vibration. One more thing you do not get with these type of enclosures is the necessary mass to damped high freq vibrations. Go ahead and tap your WB, they have a high pitch sound to them, and that is not a good thing.
What you are describing is a typical way to build light, yet stiff structures. You get the stiffness all right but Last-a-foam is a very rigid material that will do very little, if anything, to damped vibration. One more thing you do not get with these type of enclosures is the necessary mass to damped high freq vibrations. Go ahead and tap your WB, they have a high pitch sound to them, and that is not a good thing.