i just recieved my speakers and there was a manual that talked about loading the speaker with kiln sand, silica or lead shots. im a newbie so what excatly does this do to my speakers. i never heard of this till yesterday.
This normally applies to floorstanding designs, where there is often some space at the bottom of the cabinet to put heavy material, such as sand etc. The reason for 'mass loading' speakers in this way is to make them heavier, because heavier, more secure cabinets keep the drivers 'fixed'. If the drivers of your speaker are rigid in space, then they move air more efficiently. For this reason people often talk about bass being more compact or 'tight'.
If there is a dedicated 'mass loadable chamber' inside the cabinet, then it will most likely be a sealed chamber, accessed usually round the back, by a plug of some sort. Pour in the sand or load it with small bags, containing sand.
The reason your manual suggests using kiln or silica sand is because silica is a natural dessicant; in other words, it leeches out moisture. Remember that sand is prone to gathering moisture, which, if this happens, will most likely damage the cabinets from inside.
Lead shot is a good idea, as the moisture doesn't apply here.
Of course, it's not essential to use this chamber - it is said that heavy objects placed on top, such as bricks or lead weights will keep the enclosure rigid - but beware of making the whole plan turn out top heavy - you wouldn't want it to topple.
Remember though - that a good speaker cabinet is designed taking the amount of space around the drivers as part of the acoustic design. To radically alter the volume of air by loading with dense matter can sometimes cause a deadening effect in some areas. I'd say that if they've been designed with this in mind, you are okay to load them at the bottom. Try and use something which you can remove, or alter the mass, just in case the sound isn't exactly to you liking.
So in conclusion - heavier, more rigid speakers make for tighter bass so that notes seem to stop and start more realistically. Spiked feet on the bottom are also a good measure to employ, too.