Well, it really depends.
1. Your Contection
2. The hosts contection
3. The amount of bricks, emitters, models, player, anything, and everything rendered by your computer.
To improve 1. Get a better contection, not much else to say.
To improve 2. There is nothing you can do.
To improve 3. Lower the quality of everthing in your options menu. Or, reduce draw distance.