[VICIII]

I just bought VR-3 and I am impressed.  I have them running with a SVS sub.  Yamaha M-45 Amp and  C-65 preamp.
They are much more efficient than I would have thought.
Does anyone have info on filling sand in the top of the speaker to help out he mid and highs?  It seems like putting sand where it could touch the back of the rear-facing tweeter might be a bad idea.  The read of the tweeter seems like it is solid but to pile sand around it while you have sound waves trying to drive the sand anywhere it would fit seems like I would be asking for trouble.
So anyone have experience?  Is there supposed to be a cover that I am missing? 
I can tell sand was in there at one time. 

[SundayNiagara]

Contact VSA.

[LesterSleepsIn]

Yes, there is a chamber to fill with sand:

“The cabinet construction is exceptional. Primarily, it uses one inch mdf throughout. The mdf panels are thicker in some areas of the bass cabinet, up to 1.5 inches, to increase rigidity and more evenly distribute cabinet resonances. The novel feature of this design is the use of sand! Yes sand. There is a chamber, accessible from the top, to fill the area behind the midrange enclosure. Why? Sand mass loads the cabinet, bringing its already imposing 95 lb. shipping weight up to a back spasming 130 lbs. As well, the sand further damps the midrange. The goal is increased midrange and high-frequency detail, transparency, and palpability.”

https://www.soundstagenetwork.com/das_vr3.htm

Cheers,
Lester