I have often had students ask about the effect that bridge adjusters have on the sound of the instrument and what type of material that works best for these adjusters (aluminum, brass, maple, or the like). Here is a comprehensive study of the effects of these materials on the tone of the double bass. The study is very detailed and is complete with frequency decay analysis, and audio samples of basses with the various bridge adjusters installed. The results are pretty much what I have found when experimenting on double basses with these different adjusters installed.
Check out the study here. Double bass geeks will love this.