Sd, Cms, Mmd, Re, Bl, Rms, and Le are the driver parameter inputs. You want to enter Sd, Re, and Le first. The other parameters Hornresp will calculate for you by double clicking the blocks, and entering the required info. I do them in order as well, so Cms, Mmd, Bl, and then Rms. You will need the common parameters Vas, Fs, Qes, and Qms to calculate them.