Just as arrows need matching to the bow a new string can require tuning to the bow. Brace height makes a difference, as does silencer type and placement. Optimum silencer location can be found by first adjusting brace height (without silencers) to the lowest noise level (start with low brace and work to higher brace). Once you've found the height where the twang is most quiet (but it'll still be loud), tie on temporary silencers (pieces of cloth will do) on each end of the string, starting from near the respective limb tips and sliding them gradually towards center of string after each shot, a half-inch at a time. When you find the two 'sweet spots' (quietest spots) with the cloth, install your favorite silencer material at those points (same distance from the respective limb tips) and you're done.
BTW, I've found wrap-on yarn puffs to work best as silencers, though rubber whiskers also work well and are more water-resistant. Beaver and other fur balls don't work so well, but they do look nice.
Experiment a little...you'll find what works.