I found the treble and upper midrange on my SC-IIIs somewhat hashy, dry and grainy before installing 3 Audiopoints on each of the plinths. The Audiopoints made the sound much more cohesive from top to bottom, and greatly enhanced focus and clarity.
I don't bi-wire my SC-IIIs, so in an effort to eliminate the need for an external jumper I pulled the rear crossover cover to hook up all the low and high +/- leads to one set of binding posts. I discovered that 1) the nuts that secure the hookup tabs to the binding posts were only hand tightened, and 2) I found in one crossover that a lead from a capacitor had a broken solder joint. After fixing the solder joint, and tightly securing the low and high +/- tabs to one set of binding posts there was a nice improvement in resolution and coherency. The short version is you might want to check the internal connections on your SC-IVs to make sure everthing is tight and there are no loose or broken connections.
I don't bi-wire my SC-IIIs, so in an effort to eliminate the need for an external jumper I pulled the rear crossover cover to hook up all the low and high +/- leads to one set of binding posts. I discovered that 1) the nuts that secure the hookup tabs to the binding posts were only hand tightened, and 2) I found in one crossover that a lead from a capacitor had a broken solder joint. After fixing the solder joint, and tightly securing the low and high +/- tabs to one set of binding posts there was a nice improvement in resolution and coherency. The short version is you might want to check the internal connections on your SC-IVs to make sure everthing is tight and there are no loose or broken connections.