Pro-Ject Bach - Manual (Page 6)

OPTIONAL SANDFILLING
Some of our floorstanding models feature an additional hidden
chamber accessible through the base that may be sand filled
for the final touch in system tuning. Sand filling is an
easy and cheap way to improve the reproduction of the bass
range. It raises the weight and stability of the system and
quiets the enclosures throughout a remarkable damping
effect. To fill in the sand, put the speaker on the top on a
soft cloth to protect the cabinet. Then fill in the sand through
the central hole at the base until the chamber is completely
filled up and seal it with the black stubble.
!Do not use moist sand - it can damage the wooden cabinet!
MAINTENANCE
Your speaker cabinets can be cleaned periodically with a soft,
slightly damp cloth. It is not necessary to wax them. Our
cabinets feature a smooth but strong finish. Still, please keep
them out of direct sunlight and heat, since the colour of the
veneer would pale. Should the bass drivers become dusty, it
is safe to use a soft brush to clean the woofers.
* Under NO circumstances should you attempt to clean dust
from the tweeter. Doing so will damage the delicate silk
domes.