Q. If one is saying one of the sheva brachos, does he need to listen to all the other sheva brachos (which is not always possible because some people don’t enunciate the words clearly, or for some other reason)? Since all the brachos are me’akev one another. Or is it OK even if he did not hear the other brachos?

A. The sheva brochos are actually not meakev nor essential to each other. Therefore, if no one present knows to recite them all, they should still recite the ones they can. (Maseches Kalo Rabbosei 1: 1, Tanya Rabbosei 91, Atzei Arozim 62: 1, China Vechisda 1: 110, et. al. See Yabia Omer 5: 12 that debates the issue).
Horav Shlomo Miller’s Shlit’a opinion is that on the onset all brochos should be recited taking care that both the chosson and the kallah are listening to all of them. Bedieved, after the fact, if they didn’t hear them all, but ten people where there with the chosson and the kallah listening, they complied and the brochos don’t have to be repeated. Both, the Chosson and the Kallah, have to hear the brocho on the wine in order to drink from it.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a