Just to share my experience.
I just replaced my K-77M driver-to-horn gasket with the "Garlock Style 3000 Blue-gard compressed non-asbestos" sheet gasketing (1/32 inch thickness).
I could hear the improvement especially (at least to my hearing) it eliminates the high-end distortion that usually heard whenever I maximised the treble gain on my pre-amp (I'm using VTA-12 tubes pre amp).
Does anybody has the same experience by replacing their K-77 driver-to-horn gaskets especially when there are NO aftermarket gaskets for K-77M driver-to-horn?
My Cornwalll is the 1981 version with all original stocks and Bob Crites' B2 crossovers inside.
Cheers,
Jimmy