I have a Mordaunt Short 914. There is a cabin for Sand Filling. I have not fill it with sand yet. Whats the advantage and disadvantage if I fill it or not?
Mass loading is for the purpose of weighing down the speaker to reduce cabinet resonances that may color the sound.
The disadvantage is it makes the speaker or stand heavy as all heck and moving requires you to empty out the compartment/stand first. Be sure you have the speaker or stand exactly where you want it before you fill `er up.
If the compartment in the speaker is wood, I would use lead shot instead of sand. Less chance of moisture intrusion and potential long term problems.
Ellison - Tevo is all too correct! Most people think sand rejects moisture - but just the opposite is true! I made the mistake - once - of putting some sand in a container - but there was apparently just enough moisture in that sand to create mildew and wood-rot in the container. Putting sand in a speaker compartment might lead to the same problem.
Of course, you could always seal up the sand in a tightly-sealed plastic bag - as I've done with a weight on top of my CD player. Sand inside a plastic bag, covered with a dark sock - so it's not very visible in the cabinet. Just be sure to seal up any sand you use.
Be sure you have the speaker or stand exactly where you want it before you fill `er up.