The stiffest and heaviest brace on a guitar is the bridge. Changing the mass and/or the design of this important element will have discernible effects on the sound of the strings.
- A relatively heavy bridge will cause the attack (response) to be slow when compared to a relatively light bridge.
- A relatively heavy bridge will also reduce the overall volume as it takes more energy to move a heavier object than a light one. Thus a heavier bridge makes for a less responsive guitar.
- However the law of inertia implies that it will also take longer for the heavier bridge to stop vibrating (An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.) So the heavier bridge augments sustain. How much that matters with the weights involved here is debatable.
Taking all this into account, my approach is to go for maximum attack and volume by using relatively light weight woods for bridges. My target weight is 20 grams for the bridge, not including the saddle. Using a lighter wood like sapele, I can get a bridge as light as 14 grams, which includes a tie block overlay of a denser wood like ebony or gidgee. I also save a few grams by making the saddle from a dense wood like african blackwood or snakewood. The end result, when used in conjunction with properly built composite soundboard with diamond bracing is a very loud and responsive guitar. No one has complained of lacking sustain on these instruments.