Ducchau, here is what ProAc says about filling the sand cavity......
Quote
"After removing the cover the cavity should be part filled with dry silver sand, then the listener is invited to add or subtract sand, which will tune the bass quality for his taste and room acoustics. As a general rule of thumb, a small amount of sand will give the bass more warmth, adding more sand to the cavity will give a dryer tighter quality, most people will find that half to two thirds full is optimum in most models."
>>>>>>>>>>>>>>>
Also, I assume you are using spikes on the speaker plynth.
.
Quote
"After removing the cover the cavity should be part filled with dry silver sand, then the listener is invited to add or subtract sand, which will tune the bass quality for his taste and room acoustics. As a general rule of thumb, a small amount of sand will give the bass more warmth, adding more sand to the cavity will give a dryer tighter quality, most people will find that half to two thirds full is optimum in most models."
>>>>>>>>>>>>>>>
Also, I assume you are using spikes on the speaker plynth.
.