I would be concerned about putting this in a speaker as you have just created an internal acoustically reflective interface in the speaker box and changed the compressability by replacing compressable air with much less compressable sand (air volume modified). This will change the back pressure on the woofer cone and will alter the resonance frequency of the woofer.
I am surprised any speaker manufacturer would actually recommend this (unless the box was designed with space for the sand).
It is also well known that sandy or unconsolidated top soil can turn to liquid during earthquakes (low frequency vibrations).
If you think that having a liquid inside your speaker is good then by all means use sand...perhaps the sound will be more "liquid".
See these two URL's for more info
http://stilton.tnw.utwente.nl/people/rene/animations/3-big03m.mpg
http://stilton.tnw.utwente.nl/people/rene/Granular.html
I am surprised any speaker manufacturer would actually recommend this (unless the box was designed with space for the sand).
It is also well known that sandy or unconsolidated top soil can turn to liquid during earthquakes (low frequency vibrations).
If you think that having a liquid inside your speaker is good then by all means use sand...perhaps the sound will be more "liquid".
See these two URL's for more info
http://stilton.tnw.utwente.nl/people/rene/animations/3-big03m.mpg
http://stilton.tnw.utwente.nl/people/rene/Granular.html